DOE/NETL-2006/1235 

August 2006 

Estimating Freshwater Needs to Meet Future 

Thermoelectric Generation Requirements 
Disclaimer

This report was prepared as an account of work sponsored by an agency of 

the United States Government. Neither the United States Government nor 

any agency thereof, nor any of their employees, makes any warranty, 

express or implied, or assumes any legal liability or responsibility for the 

accuracy, completeness, or usefulness of any information, apparatus, 

product, or process disclosed, or represents that its use would not infringe 

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product, process, or service by trade name, trademark, manufacturer, or 

otherwise does not necessarily constitute or imply its endorsement, 

recommendation, or favoring by the United States Government or any 

agency thereof. The views and opinions of authors expressed therein do 

not necessarily state or reflect those of the United States Government or 

any agency thereof. 
Estimating Freshwater Needs to Meet Future 

Thermoelectric Generation Requirements

DOE/NETL-2006/1235 

August 2006 

NETL Contact: 

Sarah Forbes 

Technical Monitor 

Office of Systems Analyses and Planning 

Prepared by: 

Gary J. Stiegel, Jr., Andrea McNemar, Michael Nemeth, 

Brian Schimmoller, James Murphy, and Lynn Manfredo 

Research and Development Solutions, LLC 

National Energy Technology Laboratory 

www.netl.doe.gov 
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Table of Contents 

Executive Summary.......................................................................................................... 1 

Introduction....................................................................................................................... 6 

Energy-Water Issues...................................................................................................... 7 

Water Availability ....................................................................................................... 7 

NETL Energy-Water R&D Program ............................................................................ 8 

Previous Water Needs Analysis..................................................................................... 9 

Water Requirements for Thermoelectric Generation................................................. 10 

Projections of Thermoelectric Capacity and Generation............................................ 13 

Assumptions and Methodology...................................................................................... 17 

Step 1: Develop model plants....................................................................................... 18 

Fresh versus Saline Water........................................................................................ 18 

Step 2: Calculate water withdrawal and consumption factors................................... 19 

Evaporative Loss Associated with Once-Through Cooling Systems ........................ 19 

Subcritical versus Supercritical Boiler for New Coal-Fired Power Plants ............. 19 

Flue Gas Desulfurization Systems for Retrofit and New Coal-Fired Power Plants. 19 

Integrated Gasification Combined Cycle Plants...................................................... 20 

Natural Gas Combined Cycle Plants........................................................................ 20 

Step 3: Quality Control and Model Validation ........................................................... 20 

Step 4: Develop Future Cases...................................................................................... 23 

Step 5: Calculate regional withdrawal and consumption to 2030 ............................. 24 

Results.............................................................................................................................. 24 

Thermoelectric Generation - National........................................................................ 24 

National Level Results................................................................................................. 25 

Thermoelectric Generation - Regional........................................................................ 33 

Coal-Fired Generation - National............................................................................... 41 

National Conventional Coal Results........................................................................... 42 

Coal-Fired Generation - Regional .............................................................................. 44 

Comparison of 2004 & 2006 study projections........................................................... 50 

Conclusions...................................................................................................................... 52 

Appendix A................................................................................................................... A-1 

Appendix B................................................................................................................... B-1 

Appendix C................................................................................................................... C-1 

Appendix D.................................................................................................................... D-1 

Appendix E .....................................................................................................................E-1 

Appendix F .....................................................................................................................F-1 

References...................................................................................................................... R-1 
Executive Summary 

Growing concerns about freshwater availability must be reconciled with growing demand 

for power if the United States is to maintain economic growth and current standards of 

living. Thermoelectric generating capacity is expected to increase by nearly 22% 

between 2005 and 2030, based on the Energy Information Administration’s (EIA) Annual 

Energy Outlook 2006 (AEO 2006) projections.1

 A previous water needs analysis 

conducted by the Department of Energy’s National Energy Technology Laboratory 

(DOE/NETL) in 2004 suggested that national freshwater withdrawals may increase 

slightly or decline depending on assumptions made, while freshwater consumption will 

likely increase dramatically.2

 However, regional water impacts can be significantly 

different than national data averages might suggest. To characterize the significance of 

the regional impacts on water use, this report compares regional electricity demand and 

capacity forecasts from AEO 2006 with representative water withdrawal and 

consumption estimates to identify regions where water issues could become acute. 

Future freshwater withdrawal and consumption requirements for the U.S. thermoelectric 

generation sector were estimated for five cases, using AEO 2006 regional projections for 

capacity additions and retirements:a

Case 1 – Additions and retirements are proportional to current water source and type of 

cooling system. 

Case 2 – All additions use freshwater and wet recirculating cooling, while retirements are 

proportional to current water source and cooling system. 

Case 3 – 90% of additions use freshwater and wet recirculating cooling, and 10% of 

additions use saline water and once-through cooling, while retirements are proportional to 

current water source and cooling system. 

Case 4 – 25% of additions use dry cooling and 75% of additions use freshwater and wet 

recirculating cooling. Retirements are proportional to current water source and cooling 

system. 

Case 5 – Additions use freshwater and wet recirculating cooling, while retirements are 

proportional to current water source and cooling system. Five percent of existing 

freshwater once-through cooling capacity is retrofitted with wet recirculating cooling 

every five years starting in 2010. 

Summary results for the five cases, on a national basis, are presented in Table ES-1. For 

all cases, withdrawal is expected to decline, and consumption is expected to increase. 

These results are consistent with current and anticipated regulations and industry practice, 

which favor the use of freshwater recirculating cooling systems that have lower 

withdrawal requirements, but higher consumption requirements, than once-through 

cooling systems. Case 5 provides the most extreme water consumption impacts. 

Converting a significant share of existing once-through freshwater power plants to 

recirculating freshwater plants significantly reduces water withdrawal, but significantly 

increases water consumption. Case 4 indicates that dry cooling could have a significant 

 

a

 See Table 7 in the body of the report for a description of the rationale behind each of these cases and their 

assumptions. 

Freshwater Needs for Thermoelectric Generation, August 2006 

1 
impact on water consumption; compared to Cases 1-3, which have an average 

consumption of 8.1 BGD, Case 4 results in a 7% decline, equivalent to more than 200 

billion gallons per year. 

Table ES-1 - Thermoelectric Water Impacts, National Results 

Freshwater withdrawal or consumption (BGD) 

2005 2010 2015 2020 2025 2030 

Withdrawal 149.2 152.7 145.6 147.6 148.8 148.4 Case 1 

Consumption 6.2 6.6 6.8 7.3 7.6 7.9 

Withdrawal 149.2 149.4 141.0 138.6 138.0 136.3 Case 2 

Consumption 6.2 6.7 6.9 7.5 7.9 8.2 

Withdrawal 149.2 149.4 140.9 138.5 137.9 136.1 Case 3 

Consumption 6.2 6.6 6.9 7.4 7.8 8.1 

Withdrawal 149.2 149.3 140.8 138.3 134.6 135.4 Case 4 

Consumption 6.2 6.6 6.8 7.3 7.4 7.5 

Withdrawal 149.2 137.7 122.7 114.2 109.4 103.7 Case 5 

Consumption 6.2 6.9 7.4 8.2 8.7 9.2 

Each of the cases used different assumptions (see Table 7 for rationale behind each case 

and their assumptions). Due to the differences in assumptions, none of the cases can 

truly be considered a baseline for comparison with other cases. However, the year 2005 

can be used as a baseline against which to measure projected future withdrawal and 

consumption. As seen in the 2005 column of Table ES-1, the 2005 withdrawal and 

consumption values for each case are the same. Using this baseline, Table ES-2 was 

generated to show the percent change from the 2005 baseline to each of the future years. 

The negative values in Table ES-2 for withdrawal indicate decreased withdrawal while 

the positive consumption values indicate increasing consumption over time. 

Table ES-2 – Percent Change from 2005 Baseline, National Results 

Percent change from 2005 baseline 

2010 2015 2020 2025 2030 

Withdrawal 2.3 -2.4 -1.1 -0.3 -0.5 Case 1 

Consumption 6.5 9.7 17.7 22.6 27.4 

Withdrawal 0.1 -5.5 -7.1 -7.5 -8.6 Case 2 

Consumption 8.1 11.3 21.0 27.4 32.3 

Withdrawal 0.1 -5.6 -7.2 -7.6 -8.8 Case 3 

Consumption 6.5 11.3 19.4 25.8 30.6 

Withdrawal 0.1 -5.6 -7.3 -9.8 -9.2 Case 4 

Consumption 6.5 9.7 17.7 19.4 21.0 

Withdrawal -7.7 -17.8 -23.5 -26.7 -30.5 Case 5 

Consumption 11.3 19.4 32.3 40.3 48.4 

A comparison of the 2004 and 2006 analysis was conducted for quality control purposes. 

Even though the 2004 water needs analysis and the 2006 water needs analysis were 

conducted using different analytical methodologies, different time periods, and different 

cases, the results are in general agreement. National water withdrawal totals for the two 

analyses are within about 20% of each other for a given year, and the majority of this 

Freshwater Needs for Thermoelectric Generation, August 2006 

2 
difference can be traced to differences in capacity projections, differences in apportioning 

additions and retirements between once-through and recirculating systems, and the 10-

year time lag between the base years for the two studies (with the 2004 and 2006 studies 

using a base year of 1995 and 2005 respectively). National consumption totals don’t 

exhibit the same degree of numerical similarity as the withdrawal totals between the 2004 

and 2006 analyses, but the consumption trends across equivalent 25-year time periods are 

in the same direction and of similar magnitude. These observations will be addressed in 

the results section of this report. 

The regional component of the 2006 water needs analysis revealed some significant 

differences from the national averages. For example, consider Case 2, which represents a 

plausible future cooling system scenario. The national percent changes in Table ES-2 

indicate that water withdrawal will fall by 8.6% and that water consumption will rise by 

32.3% between 2005 and 2030. As shown in Figure ES-1 and Figure ES-2 on a regional 

basis, however, water withdrawal ranges from a 25% increase in Florida to a 30% decline 

in Texas; and while freshwater consumption increases in all regions, the biggest gains 

come in California (352%), Florida (199%), New York (132%) and the Rocky 

Mountain/desert southwest region (74%). 

Figure ES-1 – Average Daily Regional Freshwater Withdrawal for Thermoelectric Power Generation 

– Case 2 

-10.00

0.00

10.00

20.00

30.00

40.00

50.00

NPCC/NE

NPCC/NY

ECAR

MAIN

MAAC

MAPP

SERC

FRCC

SPP

ERCOT

WECC/RM

WECC/NWPP

WECC/CA

Withdrawals (BGD)

Water withdrawal, 2005 Incremental water withdrawal, 2005-2030

Case 2

Freshwater Needs for Thermoelectric Generation, August 2006 

3 
Figure ES-2 - Average Daily Regional Freshwater Consumption for Thermoelectric Power 

Generation – Case 2 

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

NPCC/NE

NPCC/NY

ECAR

MAIN

MAAC

MAPP

SERC

FRCC

SPP

ERCOT

WECC/RM

WECC/NWPP

WECC/CA

Consumption (BGD)

Water consumption, 2005 Incremental water consumption, 2005-2030

Case 2

The regional results reflect recent U.S. population shifts. Regions with strong population 

growth, such as the southeast and southwest, exhibit high growth in water consumption 

requirements, while regions with minimal to modest population growth, such as the 

midwest and mid-Atlantic, exhibit modest growth in water consumption requirements. 

Specific to coal-fired generation, the analysis projects that by 2030, average daily 

national freshwater withdrawals may decrease to 66.0 BGD or increase to 98.2 BGD 

from a baseline level of 91.6 BGD, depending upon case assumptions. The 2005 baseline 

coal-fired plant withdrawal represents 61% of the total thermoelectric plant withdrawal. 

Average daily national freshwater consumption resulting from U.S. coal-fired power 

generation could reach 3.4 BGD to 4.0 BGD from a baseline level of 2.3 BGD, 

depending upon case assumptions. The 2005 baseline coal-fired plant consumption 

represents 37% of the total thermoelectric plant consumption. Case 2, coal-fired, 

regional water withdrawal and consumption are illustrated in Figures ES-3 and ES-4 

respectively. 

Freshwater Needs for Thermoelectric Generation, August 2006 

4 
Figure ES-3 – Average Daily Regional Freshwater Withdrawal for Coal-Fired Power Generation – 

Case 2 

-5.00

0.00

5.00

10.00

15.00

20.00

25.00

30.00

NPCC/NE

NPCC/NY

ECAR

MAIN

MAAC

MAPP

SERC

FRCC

SPP

ERCOT

WECC/RM

WECC/NWPP

WECC/CA

Withdrawals (BGD)

Water withdrawal, 2005 Incremental water withdrawal, 2005-2030

Case 2

Figure ES-4 - Average Daily Regional Freshwater Consumption for Coal-Fired Power Generation – 

Case 2 

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

NPCC/NE

NPCC/NY

ECAR

MAIN

MAAC

MAPP

SERC

FRCC

SPP

ERCOT

WECC/RM

WECC/NWPP

WECC/CA

Consumption (BGD)

Water consumption, 2005 Incremental water consumption, 2005-2030

Case 2

Freshwater Needs for Thermoelectric Generation, August 2006 

5 
This analysis and accompanying report were completed to estimate future freshwater 

needs both for coal-fired generation and for total thermoelectric generation. The results 

from this report will be used as a base forecast against which to compare 

accomplishments in freshwater withdrawal and consumption reductions. Additionally, 

report results will be used to better understand the regional impacts of constrained water 

resources. 

Introduction 

The purpose of this report is to estimate future freshwater needs for thermoelectric power 

generation. Thermoelectric power plants – coal, oil, natural gas and nuclear fueled power 

generators using a steam turbine based on the Rankine thermodynamic cycle – require 

significant quantities of water for generating electrical energy.b For example, a 500-MW 

coal-fired power plant uses over 12 million gallons per hour of water for cooling steam 

turbine exhaust.3,c The water required for thermoelectric plants is withdrawn primarily 

from large volume sources, such as lakes, rivers, oceans, and underground aquifers. 

While both freshwater (approximately 70%) and saline water (approximately 30%) are 

currently used for thermoelectric generation, this report focuses on freshwater because 

freshwater sources are becoming increasingly strained.4 Water consumption is used to 

describe the loss of that water, typically through evaporation into the air. The United 

States Geological Survey (USGS) estimated that thermoelectric generation accounted for 

approximately 39% of freshwater withdrawals, ranking only slightly behind agricultural 

irrigation as the largest source of freshwater withdrawals in the United States in 2000.4

 

However, the corresponding water consumption associated with thermoelectric 

generation accounted for only 2.5% of total U.S. freshwater consumption in 1995.5 As 

U.S. population and associated economic development continues to expand, the demand 

for electricity will increase. The Energy Information Administration’s (EIA) latest 

forecast estimates U.S. thermoelectric generating capacity will grow from approximately 

704 GW in 2005 to 872 GW in 2030.6 As such, thermoelectric power plants may 

increasingly compete for freshwater with other sectors such as domestic, commercial, 

agricultural, industrial, and in-stream use – particularly in regions of the country with 

limited freshwater supplies. In addition, current and future water-related environmental 

regulations and requirements will also challenge the operation of existing power plants 

and the permitting of new thermoelectric generation projects. 

 

b

 Natural gas- and oil-fired combustion turbines are not sources of thermoelectric generation. 

c

 Most of today’s power plants use water as the cooling medium and the amount of water required to 

condense the steam turbine exhaust is similar whether an open-loop or closed-loop cooling system is used 

depending on design conditions. Open-loop cooling systems continuously withdraw water from a local 

water source, and return the same quantity of water to the source. Closed-loop cooling systems circulate a 

similar total volume of water as open-loop systems for a given plant size, but only withdraw a limited 

amount of water to replace evaporative loss and blowdown. Additional information on power plant water 

requirements can be found beginning on page 11 of this report. 

Freshwater Needs for Thermoelectric Generation, August 2006 

6 
Energy-Water Issues 

At the nexus of water and energy lies a wide variety of societal issues, policy and 

regulatory debate, environmental questions, technological challenges, and economic 

concerns. Water is emerging as a significant factor in economic development activities. 

Planning efforts must consider the availability and quality of water resources in a given 

locality or region to ensure that supplies are available to accommodate existing and future 

water consumers over the long term. Failure to do so can result in stunted growth, 

economic flight, inequitable development, and even open conflict. In order for the power 

industry to be ecologically responsible, technologically ready, and economically stable, 

advanced research is imperative. Energy-water issues have become increasingly visible 

in recent years, with a variety of concerns on the mind of industry, regulators, Congress, 

DOE, and the general public. A sampling of these issues includes the passing of the 

Energy Policy Act of 2005; repeated introduction of the Energy-Water Efficiency and 

Supply Technology Bill; increasingly severe regional drought conditions across the 

country; additional difficulty siting new power generating facilities in arid regions; and 

further media attention and public concern over water availability and supply. The 

following is a brief summary of some of the technical, regulatory, and political issues that 

help explain the importance of water to thermoelectric generation. Additional 

background information on energy-water issues is presented in Appendix A. 

Water Availability 

Water shortages, potentially the greatest challenge to face all sectors of the United States 

in the 21st century, will be an especially difficult issue for thermoelectric generators due 

to the large amount of cooling water required for power generation. According to a GAO 

2003 report7

, national water availability has not been comprehensively assessed in 25 

years, thus water availability on a national level is ultimately unknown. However, as the 

report goes on to say, current trends indicate that demands on the nation’s supplies are 

growing while the nation’s capacity to store surface-water is increasingly more limited 

and ground-water is being depleted. 

Water availability issues are intensified by the fact that population increases are occurring 

in water-stressed areas. Figure 1 shows the percent change in population by state from 

1990 to 2000 and Figure 2 displays mean annual precipitation from 1890 to 2002. 

Comparison of the figures shows that areas where precipitation is low, especially in the 

southwest, are also areas of greatest population growth. 

Freshwater Needs for Thermoelectric Generation, August 2006 

7 
Figure 1 - Percent Change in Population by State: 1990 to 20008

Figure 2 - Mean Annual Precipitation, 1890 to 20029,10

NETL Energy-Water R&D Program 

The U.S. Department of Energy, Office of Fossil Energy’s National Energy Technology 

Laboratory (DOE/NETL) is carrying out a comprehensive, integrated research and 

development (R&D) effort under its Innovations for Existing Plants (IEP) Program. The 

overall goal of the IEP Program is to enhance the efficiency and environmental 

performance of the existing fleet of coal-fired power plants, which represent more than 

300 gigawatts (GW) of generating capacity, and apply novel concepts to advanced power 

Freshwater Needs for Thermoelectric Generation, August 2006 

8 
systems. The program goal is to ensure that technologies are available for deployment by 

2015 that can reduce power plant freshwater withdrawal and consumption by 5% to 10% 

while minimizing the impacts of power plant operation on water quality. To achieve this 

goal, the energy-water interface portion of the IEP program conducts research in four 

areas: Non-Traditional Sources of Process and Cooling Water; Innovative Water Reuse 

and Recovery; Advanced Cooling Technology; and Advanced Water Treatment and 

Detection Technology. The portfolio of energy-water nexus technology R&D projects 

encompasses laboratory studies, modeling, and pre-commercial demonstration full-scale 

testing. Project success is intimately tied to key collaborations and partnerships with 

industry, federal, state, and local agencies, and the academic and research communities. 

This water needs analysis was conducted in support of the IEP energy-water R&D 

activity. 

Previous Water Needs Analysis 

In 2004, NETL conducted a similar water needs analysis to estimate how thermoelectric 

power plants will impact national freshwater resources through 2025.2

 Using the EIA 

2004 Annual Energy Outlook’s reference case forecast for electricity generating capacity, 

future freshwater requirements for both total and coal-based thermoelectric generation 

were estimated and compared to current and past water use by the power sector. A 

number of different cases were considered to reflect uncertainties about the source of 

cooling water (fresh or saline) and the cooling technology used by the new and retired 

capacity projected by EIA. 

Case 1 - All additions and retirements occur at facilities using freshwater. 

Case 2 - Additions and retirements are proportional to current source withdrawals (70% 

freshwater/30% saline). 

Case 3 - All additions and retirements occur at facilities using saline water. 

Case 4 - Additions occur at freshwater facilities, while retirements occur at saline 

facilities. 

Case 5 - Additions occur at saline facilities, while retirements occur at freshwater 

facilities. 

Case 6 - All retired coal units are assumed to be once-through cooling. These units are 

repowered rather than retired but the existing once-through cooling system continues to 

be used. New capacity additions are reduced by the repowered units.

The result of these case runs indicated that the amount of freshwater needed to meet 

forecasted increases in U.S. thermoelectric capacity over the next two decades could 

increase slightly or decline to some degree in terms of withdrawal. The analysis 

projected that by 2025 daily freshwater withdrawals required to meet the needs of U.S. 

thermoelectric power generation could decrease to 113 billion gallon per day (BGD) or 

increase to 138 BGD depending upon the assumptions made about source of cooling 

water and type of cooling technology employed for new and retired capacity. This 

compared with USGS estimates that thermoelectric power plants withdrew approximately 

132 BGD of freshwater in 1995 and approximately 136 BGD of freshwater in 2000. 

Freshwater Needs for Thermoelectric Generation, August 2006 

9 
In terms of consumption, several cases projected a large increase on a percentage basis as 

older once-through cooling plants are replaced by new plants with recirculating cooling 

systems. The 2004 study projected that by 2025, 3.3 to 8.7 BGD could be consumed 

compared to USGS estimates that in 1995, freshwater consumption was 3.3 BGD. 

The 2006 analysis includes an additional level of detail and resolution that requires a 

modified methodology from that used in the 2004 analysis. While the 2004 analysis 

looked at freshwater requirements on a national basis, it was recognized that there are 

significant regional differences in projected electricity growth and freshwater demand 

and availability. As a result, the 2006 analysis includes estimates of both national and 

regional water withdrawal and consumption. In addition, the 2006 analysis utilizes 

model plants with regionally specific water withdrawal and consumption factors that 

differentiate coal-fired power plant design parameters including the cooling water 

system, boiler, and flue gas desulfurization (FGD) system. Table 1 presents a 

comparison of the major assumptions and methodologies used for the 2004 and 2006 

analyses.

Table 1 - U.S. Power Generation Industry Water Withdrawal and Use Analysis – Comparison of 

Assumptions and Methodologies

Item 2004 Analysis 2006 Analysis 

Capacity/Generation 

Projections AEO 2004 AEO 2006 

Geographical Breakdown National National and NERC region 

Cooling Water Source 

Breakdown Freshwater and Saline Freshwater and Saline 

Cooling Water System Type Once-through and wet 

recirculating 

Once-through and recirculating 

(dry, wet, and cooling pond) 

Generation Type Breakdown Total thermoelectric and coal 

Total thermoelectric and coal, 

nuclear, non-coal steam, and natural 

gas combined cycle 

Final Year of Projection 2025 2030 

Cases Six cases representing upper 

and lower bounds 

Five cases with conservative 

assumptions 

Water Use Scaling Factors – 

Geographic Coverage National NERC region with adjustment for capacity factor increase 

Water Use Scaling Factors – 

Coal Plant Design Not included 

Boiler type – subcritical or 

supercritical 

FGD type – wet, dry, or none 

Water Requirements for Thermoelectric Generation 

A significant quantity of water is required for thermoelectric power plants to support 

electricity generation. The largest demand for water in thermoelectric plants is cooling 

water for condensing steam. Thermoelectric generation relies on a fuel source (fossil, 

nuclear, or biomass) to heat water to steam that is used to drive a turbine-generator. 

Steam exhausted from the turbine is condensed and recycled to a steam generator or 

Freshwater Needs for Thermoelectric Generation, August 2006 

10 
boiler. The steam condensation typically occurs in a shell-and-tube heat exchanger 

known as a condenser. The steam is condensed on the shell side by the flow of cooling 

water through tube bundles located within the condenser. Cooling water mass flow rates 

of greater than 25 times the steam mass flow rate are necessary depending on the 

allowable temperature rise of the cooling water – typically 15-25oF. The design and 

operating parameters of the cooling system are critically important to overall power 

generation efficiency. At higher condenser cooling water inlet temperatures, the steam 

condensate temperature is higher and subsequently turbine backpressure is higher. The 

turbine backpressure is inversely related to power generation efficiency: the higher the 

turbine backpressure, the lower the power generation efficiency. 

There are basically two types of cooling water system designs: once-through (open loop) 

and recirculating (closed loop). In once-through systems, the cooling water is withdrawn 

from a local body of water such as a lake, river, or ocean and the warm cooling water is 

subsequently discharged back to the same water body after passing through the 

condenser. As a result, plants equipped with once-through cooling water systems have 

relatively high water withdrawal, but low water consumption. 

There are three primary technologies used to support recirculating cooling systems – wet 

cooling towers, cooling ponds, and dry cooling towers. Some plants use a combination 

of these technologies, known as hybrid cooling systems. The most common type of 

recirculating system uses wet cooling towers to dissipate the heat from the cooling water 

to the atmosphere. Figure 3 is a schematic of a wet recirculating cooling water system 

for a 500-MW coal-fired power plant. In wet recirculating systems the warm cooling 

water is typically pumped from the condenser to a cooling tower where the heat is 

dissipated directly to ambient air by evaporation of the water and heating the air. The 

cooling water is then recycled back to the condenser. Because of evaporative losses, a 

portion of the cooling water needs to be discharged from the system – known as 

blowdown − to prevent the buildup of minerals and sediment in the water that could 

adversely affect performance. For a wet recirculating system, only make-up water needs 

to be withdrawn from the local water body to replace water lost through evaporation and 

blowdown. As a result, plants equipped with wet recirculating systems have relatively 

low water withdrawal, but high water consumption, compared to once-through systems. 

A cooling pond serves the same purpose as a wet cooling tower, but relies on natural 

conduction/convection heat transfer from the water to the atmosphere as well as 

evaporation to cool the recirculating water. 

Dry recirculating cooling systems use either direct or indirect air-cooled steam 

condensers. In a direct air-cooled steam condenser the turbine exhaust steam flows 

through air condenser tubes that are cooled directly by conductive heat transfer using a 

high flow rate of ambient air that is blown by fans across the outside surface of the tubes. 

Therefore, cooling water is not used in the direct air-cooled system. In an indirect aircooled steam condenser system a conventional water-cooled surface condenser is used to 

condense the steam, but an air-cooled closed heat exchanger is used to conductively 

 

Freshwater Needs for Thermoelectric Generation, August 2006 

11 
Figure 3 - Wet Recirculating Cooling Water System for a 500-MW Coal-Fired Boiler 

3,804,950 lb/hr 

Boiler 

Feedwater

Steam

Condensate

Warm Water

Cool Water Steam 

Condenser

Evaporation 

& Drift 

Make-up Water Blowdown Water

9,537 gpm 3,161 gpm 

25 oF Rise 

187,600 gpm 

500 MW 

6,415 gpm 

7,645 gpm 

Generator

Turbine

Cooling 

Tower

Boiler 

transfer the heat from the water to the ambient air. As a result, there is no evaporative 

loss of cooling water with an indirect-air dry recirculating cooling system and both water 

withdrawal and consumption are minimal. 

In the United States, existing thermoelectric power plants use each of these types of 

systems, with estimates indicating that 42.7% of generating capacity is once-through, 

41.9% wet recirculating, 0.9% dry cooling, and 14.5% cooling ponds.11 Table 2 presents 

a summary of the current percentage distribution of cooling technology by generation 

type. It should be noted that the data for combined cycle plants represents only about 7% 

of the total combined cycle plants currently in operation. This is because not all plants 

provided cooling data, so the table was created using what information was available at 

the time. If all plants reported cooling data, it is most likely that dry cooling would 

represent a much smaller percentage of the total combined cycle cooling. 

Table 2 - Cooling Technology by Generation Type 

Percentage (%) 

Generation 

Type 

Wet 

Recirculating 

OnceThrough Dry Cooling 

Pond 

Coal 48.0% 39.1% 0.2% 12.7% 

Fossil NonCoal 23.8% 59.2% 0.0% 17.1% 

Combined 

Cycle 30.8% 8.6% 59.0% 1.7% 

Nuclear 43.6% 38.1% 0.0% 18.3% 

Total 41.9% 42.7% 0.9% 14.5% 

Freshwater Needs for Thermoelectric Generation, August 2006 

12 
Historically, the choice of cooling technology for a particular plant depended on the 

quantity and quality of local water sources coupled with cost and performance 

characteristics of the different systems. The use of closed-loop systems, however, is 

likely to become much more pronounced in the future due to the Clean Water Act 316(b) 

provisions and public pressures.d Although once-through cooling systems can still be 

legally permitted under 316(b), the complexity of the permitting, analysis and reporting 

requirements may discourage their use. 

Projections of Thermoelectric Capacity and Generation 

The EIA publishes its Annual Energy Outlook (AEO) to provide a forecast as to where 

the energy sector will be in the future, including projections of thermoelectric capacity 

and generation. The AEO projections are based on EIA’s National Energy Modeling 

System (NEMS), which is revised yearly to reflect technology advances, supply and 

demand adjustments, and other market forces. AEO 2006 projections of capacity and 

generation to 2030 are used in this analysis to calculate future thermoelectric generation 

water withdrawal and consumption. Table 3 summarizes projected changes in U.S. 

electric power generating capacity from 2005 to 2030. Coal-fired generating capacity is 

projected to increase by 148 GW from 2005 to 2030. 

Table 3 - AEO 2006 Thermoelectric Capacity Projections – 2004 to 2030 

 2004 2005 2010 2015 2020 2025 2030 

Net Generating Capacity 

Coal Steam 309.9 309.3 318.6 319.3 345.3 390.1 457.4 

Other Fossil Steam 124.3 122.8 122.4 86.5 80.3 79.3 75.3 

Combined Cycle 158.7 171.6 183.8 189.3 213.8 225.7 230.6 

Nuclear 99.6 100.1 100.9 104.0 108.8 108.8 108.8 

Total 

Thermoelectric 692.5 703.9 725.7 699.1 748.1 803.9 872.1 

Cumulative Additions (Planned and Unplanned) - 2005 Baseline 

Coal Steam 0.0 0.4 12.0 16.3 42.2 87.0 154.4 

Other Fossil Steam 0.0 0.1 0.1 0.1 0.1 0.1 0.1 

Combined Cycle 0.0 13.5 25.7 31.2 55.6 67.6 72.5 

Nuclear 0.0 0.0 0.0 2.2 6.0 6.0 6.0 

Total 

Thermoelectric 0.0 14.0 37.8 49.8 103.9 160.7 233.0 

Cumulative Retirements - 2005 Baseline 

Coal Steam 0.0 0.9 3.0 6.8 6.8 6.8 6.8 

Other Fossil Steam 0.0 1.6 2.0 37.9 44.0 45.1 49.0 

Combined Cycle 0.0 0.6 0.6 0.6 0.6 0.6 0.6 

Nuclear 0.0 0.0 0.0 0.0 0.0 0.0 0.0 

Total 

Thermoelectric 0.0 3.1 5.6 45.3 51.4 52.5 56.4 

 

d

 See Appendix A for more details on CWA 316(b). 

Freshwater Needs for Thermoelectric Generation, August 2006 

13 
AEO 2006 also includes a breakout of thermoelectric capacity and generation by region 

using the 13 North American Electric Reliability Council (NERC) control regions, 

excluding Alaska and Hawaii. The NERC regions are shown in Figure 4 and a 

description of the regional abbreviations is provided in Table 4. 

Figure 4 - NERC Regions 

WECC/ 

NWCC 

MAIN

MAPP

ECAR

NPCC/

NY 

NPCC/ 

NE 

MACC

SERC

FRCC 

SPP ERCOT

WECC/ 

RM 

WECC/ 

CA 

Table 4 – Description of NERC Regions 

Region 

Number 

Abbreviation Region 

1 ECAR East Central Area Reliability Coordination Agreement 

2 ERCOT Electric Reliability Council of Texas 

3 MAAC Mid-Atlantic Area Council 

4 MAIN Mid-America Interconnected Network 

5 MAPP Mid-Continent Area Power Pool 

6 NPCC/NY Northeast Power Coordinating Council/New York 

7 NPCC/NE Northeast Power Coordinating Council/New England 

8 FRCC Florida Reliability Coordinating Council 

9 SERC Southeastern Electric Reliability Council 

10 SPP Southwest Power Pool 

11 WECC/NWCC Western Electricity Coordinating Council/Northwest Power 

Pool 

12 WECC/RM Western Electricity Coordinating Council/Rocky Mountains, 

AZ, NM, southern NV 

13 WECC/CA Western Electricity Coordinating Council/California 

Freshwater Needs for Thermoelectric Generation, August 2006 

14 
Figure 5 and 6 show that thermoelectric capacity (GW) and generation (billion kWh) will 

increase in most of the NERC regions by 2030, reflecting required generation to meet 

anticipated demand growth. Both capacity and generation growth are presented because 

the two are not necessarily directly linked. For example, if unutilized capacity exists in a 

region, generation can increase without a change to capacity. The regions of greatest 

growth are indicated in the figures, and correspond to the areas where water concerns are 

growing as well, particularly in the west. The FRCC region and all WECC regions show 

approximately a 50% increase in thermoelectric generating capacity. 

Figure 5 - Thermoelectric Capacity, 2005 vs. 2030, by NERC region 

0.0

50.0

100.0

150.0

200.0

250.0

NPCC/NE

NPCC/NY

ECAR

MAIN

MAAC

MAPP

SERC

FRCC

SPP

ERCOT

WECC/RM

WECC/NWPP

WECC/CA

Capacity (GW)

Thermoelectric capacity, 2005 Incremental thermoelectric capacity, 2005-2030

Regions with greater than 50% 

increase in incremental capacity - 

same as regions of growing water 

concerns

Figure 7 and Figure 8 present the same information for the portion of the total 

thermoelectric capacity and generation that correspond to coal-fired plants. Coal-fired 

capacity and generation will also increase in most of the NERC regions by 2030. The 

regions with growing water concerns are also projected to experience greater than 100% 

increase in incremental coal capacity.

Freshwater Needs for Thermoelectric Generation, August 2006 

15 
Figure 6 - Thermoelectric Generation, 2005 vs. 2030, by NERC region 

0.0

200.0

400.0

600.0

800.0

1000.0

1200.0

1400.0

NPCC/NE

NPCC/NY

ECAR

MAIN

MAAC

MAPP

SERC

FRCC

SPP

ERCOT

WECC/RM

WECC/NWPP

WECC/CA

Generation (billion kWh)

Thermoelectric generation, 2005 Incremental thermoelectric generation 2005-2030

Figure 7 – Coal-Fired Capacity, 2005 vs. 2030, by NERC region 

0.0

20.0

40.0

60.0

80.0

100.0

120.0

140.0

NPCC/NE

NPCC/NY

ECAR

MAIN

MAAC

MAPP

SERC

FRCC

SPP

ERCOT

WECC/RM

WECC/NWPP

WECC/CA

Capacity (GW)

Coal-fired capacity, 2005 Incremental coal-fired capacity, 2005-2030

Regions with greater than 100% 

increase in incremental coal capacity -

IGCC satisfies California's 500% 

demand increase for coal-fired 

electricity

Freshwater Needs for Thermoelectric Generation, August 2006 

16 
Figure 8 – Coal-Fired Generation, 2005 vs. 2030, by NERC region 

0.0

100.0

200.0

300.0

400.0

500.0

600.0

700.0

800.0

900.0

NPCC/NE

NPCC/NY

ECAR

MAIN

MAAC

MAPP

SERC

FRCC

SPP

ERCOT

WECC/RM

WECC/NWPP

WECC/CA

Generation (billion kWh)

Coal-fired generation, 2005 Incremental coal-fired generation, 2005-2030

Regions with greater than 125% 

increase in incremental coal generation 

- IGCC satisfies California's 500% 

demand increase for coal-fired 

electricity

Assumptions and Methodology 

Using the electricity capacity and generation forecasts provided by AEO 2006 and the 

water use estimates provided by EIA-767, an estimate of freshwater consumption and 

withdrawal was obtained for the U.S. thermoelectric power generation industry over the 

next 25 years. Table 5 lists the resources used for this analysis, and summarizes how 

each resource supported the analysis. 

These sources provided data from which water withdrawal and consumption factors 

(water use scaling factors) could be calculated for a given category of power plant in a 

given region. The water use scaling factors indicate average rate of water use per unit of 

electrical output – gallon per hour per kilowatt (gal/kWh). 

Figure 9 provides a flowchart depiction of the methodology used to conduct the analysis. 

A brief description of each step in the process is presented below. A more detailed 

discussion of the methodology is provided in Appendix B. 

Freshwater Needs for Thermoelectric Generation, August 2006 

17 
Table 5 – Data Resources 

Resource Type of Data 

AEO 2006 • Projections of capacity and generation by 

NERC region for coal, non-coal fossil, and 

nuclear plants 

• Coal capacity, generation, and capacity factor 

breakdown by four categories: existing 

unscrubbed, existing scrubbed, new PC 

(scrubbed), and IGCC 

NETL 2005 Coal Power Plant Database – 

Including data from 2003 EIA-767 

• Plant generation 

• Average water withdrawal and consumption 

• Cooling water source 

• Type of cooling water system 

• Type of boiler 

• Type of FGD system 

EIA-860 • Plant location by NERC region 

• Plant summer capacity 

CMU – Integrated Environmental Control Model 

(IECM) 

• Water use factors for wet FGD and dry FGD 

Parsons - Power Plant Water Consumption Study, 

August 2005 

• Water use factors for boiler make-up 

• Water use factors for IGCC plants 

Figure 9 - Methodology for the 2006 Water Needs Analysis 

Develop 

model plants 

to represent 

existing 

thermoelectric fleet

Calculate 

water 

withdrawal 

and 

consumption 

factors

Quality 

control and 

model 

validation

Develop 

future 

cases to 

evaluate

Calculate 

regional 

withdrawal 

and 

consumption 

to 2030

Step 1 Step 2 Step 3 Step 4 Step 5

Step 1: Develop model plants 

To obtain the resolution desired for this analysis, water withdrawal and consumption 

factors were determined for a large number of plant configurations, based on location, 

generation type, cooling water source, cooling system type, and where applicable, boiler 

type and type of FGD system. The existing thermoelectric fleet was segregated into 

numerous configurations, called “model plants” using data contained in several sources: 

the NETL Coal Plant Database, EIA-767, and EIA-860. 

Fresh versus Saline Water 

The analysis focuses on freshwater impacts associated with future thermoelectric power 

plants. It is recognized that saline water is used at a number of power plants in oncethrough cooling systems. However, in light of 316(b) regulations for new facilities that 

favor recirculating systems and siting difficulties for coastal-based power plants, the 

percentage of saline-based cooling systems at new plants is expected to be relatively 

Freshwater Needs for Thermoelectric Generation, August 2006 

18 
small. Furthermore, no distinction is made between surface and groundwater; both are 

included as freshwater. 

Step 2: Calculate water withdrawal and consumption factors 

For each model plant defined in Step 1, water withdrawal and consumption factors were 

calculated using the data sources outlined above. For coal-fired plants, the water 

withdrawal and consumption factors were based on the sum of three components: 

1) boiler make-up water; 2) FGD make-up water; and 3) cooling water. Average water 

withdrawal (gal/hr), average water consumption (gal/hr), and summer capacity were used 

to calculate average withdrawal and consumption scaling factors (gal/kWh) for each 

model plant in each of the NERC regions. Nuclear, oil steam, gas steam, and natural gas 

combined-cycle plants were classified according to NERC region, cooling water source 

(fresh or saline), and cooling water system (recirculating or once-through). A summary 

of the regional water withdrawal and consumption factors used in the analysis is included 

in Appendix D.

The following is a brief discussion of the more important assumptions made in 

calculating the water use factors. 

Evaporative Loss Associated with Once-Through Cooling Systems 

One important point needs to be made regarding consumption levels for once-through 

cooling systems. Although once-through consumption levels are extremely small at the 

plant boundaries, downstream consumption (evaporation) due to the elevated discharge 

temperature is not insignificant. An Electric Power Research Institute (EPRI) study 

estimated that once-through consumption levels, when including downstream 

evaporation, are less than, but of the same magnitude as, wet recirculating cooling system 

consumption levels.12 EPRI estimated once-through fossil plant water consumption 

levels of 300 gal/MWh versus closed-loop water consumption levels of 480 gal/MWh. 

For nuclear plants, the corresponding numbers are 400 gal/MWh and 720 gal/MWh. 

However, since this analysis relies on the water withdrawal and consumption data 

reported by power plants to EIA, it does not account for this downstream evaporative 

loss. 

Subcritical versus Supercritical Boiler for New Coal-Fired Power Plants 

The analysis uses different water use scaling factors for coal-fired power plants based on 

boiler type. A supercritical boiler is more efficient and therefore requires less cooling 

water flow than a subcritical boiler for an equivalent amount of electrical generation 

output. Future coal-fired plant capacity is assumed to be split as 70% supercritical and 

30% subcritical for the water analysis. Appendix C provides additional background 

information and justification for this assumption. 

Flue Gas Desulfurization Systems for Retrofit and New Coal-Fired Power Plants 

The FGD make-up water requirement depends on the type of FGD system – either wet or 

dry. Dry FGD systems require much less water than wet FGD systems, for example, so 

different factors were used. The FGD make-up water factors were calculated using 

Freshwater Needs for Thermoelectric Generation, August 2006 

19 
material balance data contained in Carnegie Mellon University’s Integrated 

Environmental Control Model (IECM).13 The amount of existing non-scrubbed capacity 

projected to be retrofit with FGD was obtained from EIA based on AEO2006 data. It 

was further assumed that all new coal-fired plants would be equipped with FGD. Since 

emission regulations do not dictate technology selection, the analysis apportions FGD 

type to retrofit and new capacity additions based on the existing split in the coal-fired 

power fleet (by summer capacity), which is 90% wet/10% dry. 

Integrated Gasification Combined Cycle Plants 

Water requirements for integrated gasification combined cycle (IGCC) plants were 

obtained from a study Parsons conducted for DOE/NETL in 2005.3 Of the several IGCC 

processes analyzed in the Parsons Study, the Conoco-Phillips E-Gas water withdrawal 

and consumption estimates were used for this analysis. The water requirements for IGCC 

facilities differ from those at pulverized coal facilities. While both require cooling water, 

IGCC requires substantially less since a large fraction of the output from an IGCC plant 

is produced from the combustion turbines, which require minimal water. Moreover, 

since IGCC relies on water for significant process (non-cooling) use, it is unlikely that a 

saline water source would be desirable. The model IGCC coal plant, therefore, is 

restricted to freshwater use. 

Natural Gas Combined Cycle Plants 

In calculating water withdrawal and consumption quantities for combined-cycle plants, 

an adjustment was made to account for the fact that the gas turbine portion of the plant 

does not require cooling water. The design capacity of the gas turbine portion of a 

combined-cycle facility is typically twice that of the steam turbine portion; in other 

words, two-thirds of a combined-cycle plant’s total output is derived from the gas 

turbine(s). Therefore, only about one-third of the plant output is used for steam 

generation, with its associated water requirements. For this analysis, water withdrawal 

and consumption factors were applied to only one-third of the combined-cycle capacity. 

Appendix E provides additional background information and justification for this 

assumption. 

Step 3: Quality Control and Model Validation 

Step 3 represents efforts designed to ensure quality control for the analysis. The water 

withdrawal and consumption factors that were used in the model were obtained through a 

rigorous statistical evaluation of data from EIA. SPSS statistical software was utilized to 

generate boxplots of data that were used to identify outliers. These outliers were not 

considered during the calculation of water withdrawal and consumption factors. The 

following is a detailed description of the process used to identify outliers. 

For each coal, fossil non-coal, and nuclear plant identified in EIA-767, a withdrawal 

usage factor (gal/MWh) was calculated. The plants were then segregated into the 

following groups by fuel, cooling system type, and boiler type (where applicable): 

Freshwater Needs for Thermoelectric Generation, August 2006 

20 
• Coal Recirculating Subcritical 

• Coal Recirculating Supercritical 

• Coal Once-Through Subcritical 

• Coal Once-Through Supercritical 

• Coal Cooling Pond Subcritical 

• Coal Cooling Pond Supercritical 

• Fossil Non-Coal Recirculating 

• Fossil Non-Coal Once-Through 

• Fossil Non-Coal Cooling Pond 

• Nuclear Recirculating 

• Nuclear Once-Through 

For once-through and cooling pond plants, withdrawal usage factors were multiplied by 

the corresponding cooling system design temperature rise to normalize the data. For 

recirculating plants, this step was not taken since the temperature rise would affect the 

size of the cooling tower, but not the amount of evaporative loss or blowdown that 

determine the make-up withdrawal rate. 

The appropriate data (gal/MWh for recirculating plants and gal/MWh x ΔT for oncethrough plants) for the above categories was collected and inserted into SPSS to generate 

boxplots of the data in each of the above categories to identify outliers. An outlier is a 

data point "far away" from the rest of the data. Some of the water usage data points 

calculated from the EIA databases were further away from the general data population 

than what seems reasonable. The outliers can indicate faulty data entry, or possibly 

unusual operation conditions. For purposes of calculating the regional water usage 

factors for this study, it was decided to identify and eliminate the statistically significant 

outliers using the box plot technique described below. 

Boxplots are a graphical tool used to identify the center, spread, extent and nature of any 

departure from symmetry, and outliers contained in a data set. To construct such a plot, 

data must be ordered in value from smallest to largest. The lower fourth and upper fourth 

of the data can then be identified. The lower fourth is the median of the smallest n/2 

observations when n is even, and the median of the smallest (n+1)/2 observations when n 

is odd. The upper fourth is the median of the largest n/2 observations when n is even, and 

the median of the largest (n+1)/2 observations when n is odd. The fourth spread, fs, is the 

difference between the upper and lower fourths. Any observation farther than 1.5fs from 

the closest fourth is a mild outlier while those observations farther than 3fs from the 

closest fourth are extreme outliers26. 

Figure 10 provides an example of a typical boxplot. In this plot, the upper edge of the 

box represents the upper fourth, while the lower edge represents the lower fourth. The 

horizontal line passing through the box indicates the median value of the data. The 

circles above and below the box indicate outliers while the vertical lines extending above 

and below the box represent the highest and lowest observations not considered outliers. 

Freshwater Needs for Thermoelectric Generation, August 2006 

21 
Figure 10 – Example Boxplot27 

Outliers identified by SPSS boxplots were eliminated from the calculation of water usage 

factors. Table 6 presents the number of data points available as well as the number of 

outliers identified in each of the 11 categories considered. 

Table 6 – Data Points and Outlier Totals for QA/QC Categories 

Category Data Points Available Outliers Eliminated 

Coal Recirculating Subcritical 199 51 

Coal Recirculating Supercritical 46 7 

Coal Once-Through Subcritical 400 71 

Coal Once-Through Supercritical 40 3 

Coal Cooling Pond Subcritical 62 0 

Coal Cooling Pond Supercritical 9 4 

Fossil Non-Coal Recirculating 88 34 

Fossil Non-Coal Once-Through 289 55 

Fossil Non-Coal Cooling Pond 6 0 

Nuclear Recirculating 39 7 

Nuclear Once-Through 55 9 

Appendix F presents SPSS boxplots generated from the original data for each of the 

above categories as well as boxplots generated after outliers were eliminated from the 

data set. 

To ensure that the estimates generated by the water needs analysis model were 

reasonable, the 2006 projections were compared to the 2004 analysis results. This 

comparison is presented in the results section. Since the 2004 projections are based on 

USGS data, comparing the 2006 results with those of the 2004 study serves to provide 

corroboration with USGS data. 

Freshwater Needs for Thermoelectric Generation, August 2006 

22 
Step 4: Develop Future Cases 

Future water withdrawal and consumption for the U.S. thermoelectric generation sector 

are estimated for five cases – one reflecting status quo conditions, two reflecting varying 

levels of regulations regarding cooling water source, one incorporating dry cooling, and 

one reflecting regulatory pressures to convert existing once-through capacity to 

recirculating capacity. Table 7 presents the description and rationale for the five selected 

cases. 

Table 7 – Case Descriptions for 2006 Water Needs Analysis 

Case Description Rationale 

Case 1: Additions and retirements 

proportional to current water source 

and type of cooling system. 

Status quo scenario case. Assumes additions and retirements 

follow current trends. 

Case 2: All additions use freshwater 

and wet recirculating cooling, while 

retirements are proportional to 

current water source and cooling 

system. 

Regulatory-driven case. Assumes 316(b) and future regulations 

dictate the use of recirculating systems for all new capacity. 

Retirement decisions hinge on age and operational costs rather 

than water source and type of cooling system. 

Case 3: 90% of additions use 

freshwater and wet recirculating 

cooling, and 10% of additions use 

saline water and once-through 

cooling, while retirements are 

proportional to current water source 

and cooling system. 

Regulatory-light case. New additions favor the use of freshwater 

recirculating systems, but some saline capacity is permitted. 

Retirement decisions remain tied to age and operational costs, 

tracking current source withdrawals. 

Case 4: 25% of additions use dry 

cooling and 75% of additions use 

freshwater and wet recirculating 

cooling. Retirements are proportional 

to current water source and cooling 

system. 

Dry cooling case. Regulatory and public pressures result in 

significant market penetration of dry cooling technology. 

Retirement decisions remain tied to age and operational costs, 

tracking current source withdrawals. 

Case 5: Additions use freshwater and 

wet recirculating cooling, while 

retirements are proportional to 

current water source and cooling 

system. 5% of existing freshwater 

once-through cooling capacity 

retrofitted with wet recirculating 

cooling every 5 years starting in 

2010. 

Conversion case. Same as Case 2, except regulatory and public 

pressures compel state agencies to dictate the conversion of a 

significant amount of existing freshwater once-through cooling 

systems to wet recirculating. 

The five cases were selected to cover the range of possible design choices for new power 

plants including the source of water (fresh or saline) and type of cooling system (wet 

recirculating or dry). In addition, Case 5 assumes that 25% of existing power plants with 

a once-through cooling system are retrofit with a wet recirculating system. For all five 

cases, it is assumed that plant retirements occur proportional to current water source and 

cooling system type. A comparison of these cases with those used in the 2004 Water 

Needs Analysis can be found in Appendix B. 

Freshwater Needs for Thermoelectric Generation, August 2006 

23 
Step 5: Calculate regional withdrawal and consumption to 2030 

Step 5 integrates the water withdrawal and consumption factors calculated in Step 2 with 

the various cases defined in Step 4 to assess the regional and national impacts on water 

withdrawal and consumption out to 2030. The Annual Energy Outlook provides 

projections of future electricity generating capacity by year, by generation type and by 

NERC region. Apportioning this capacity among the chosen model plants for a given 

case and then applying the water withdrawal and consumption factors enabled the 

calculation of estimated water withdrawal and consumption trends for each of the five 

future cases. 

Results

Water withdrawal and consumption projections for each of the five cases are presented 

below both nationally and regionally for total thermoelectric generation and the coal-fired 

generation component of thermoelectric generation. 

Thermoelectric Generation - National 

The analysis projects that by 2030, average daily national freshwater withdrawals 

required to meet the needs of U.S. thermoelectric power generation could range from 

148.4 BGD to 103.7 BGD depending upon case assumptions. This compares with USGS 

estimates that thermoelectric power plants withdrew approximately 132 BGD of 

freshwater in 1995 and approximately 136 BGD of freshwater in 2000. Table 8 presents 

the range of average daily national freshwater withdrawal for each of the five cases from 

2005 through 2030. This same data is presented graphically in Figure 11. 

Table 8 – Average National Freshwater Withdrawal for Thermoelectric Power Generation (BGD) 

 2005 2010 2015 2020 2025 2030 

Case 1 149.2 152.7 145.6 147.6 148.8 148.4 

Case 2 149.2 149.4 141.0 138.6 138.0 136.3 

Case 3 149.2 149.4 140.9 138.5 137.9 136.1 

Case 4 149.2 149.3 140.8 138.3 134.8 135.8 

Case 5 149.2 137.7 122.7 114.2 109.4 103.7 

Maximum 149.2 152.7 145.6 147.6 148.8 148.4 

Minimum 149.2 137.7 122.7 114.2 109.4 103.7 

The analysis projects that by 2030, average daily national freshwater consumption 

resulting from U.S. thermoelectric power generation could range from 7.8 BGD to 9.2 

BGD depending upon case assumptions. This compares with USGS estimates that in 

1995, freshwater consumption by U.S. thermoelectric power plants was approximately 

3.3 BGD. Table 9 presents the range of average daily national freshwater consumption 

for each of the five cases from 2005 through 2030. This same data is presented 

graphically in Figure 12. 

Freshwater Needs for Thermoelectric Generation, August 2006 

24 
Figure 11 – Average Daily National Freshwater Withdrawal for Thermoelectric Power Generation 

0.0

20.0

40.0

60.0

80.0

100.0

120.0

140.0

160.0

180.0

2005 2010 2015 2020 2025 2030

Year

Daily Withdrawals (billion gpd)

600

650

700

750

800

850

900

Thermoelectric Generating Capacity (GW)

Case 1

Case 2

Case 3

Case 4

Case 5

Thermoelectric Capacity

Table 9 – Average National Freshwater Consumption for Thermoelectric Power Generation (BGD) 

 2005 2010 2015 2020 2025 2030 

Case 1 6.2 6.6 6.8 7.3 7.6 7.9 

Case 2 6.2 6.7 6.9 7.5 7.9 8.2 

Case 3 6.2 6.6 6.9 7.4 7.8 8.1 

Case 4 6.2 6.6 6.9 7.3 7.6 7.8 

Case 5 6.2 6.9 7.4 8.2 8.7 9.2 

Maximum 6.2 6.9 7.4 8.2 8.7 9.2 

Minimum 6.2 6.6 6.8 7.3 7.6 7.8 

National Level Results 

Case 1 

Total thermoelectric generation freshwater withdrawal is projected to remain relatively 

constant from 2005 through 2030 for Case 1 – decreasing slightly from 149.2 BGD to 

148.4 BGD – despite the overall 23% increase in generation capacity from 704 GW to 

865 GW. At first glance this result seems inconsistent with the Case 1 status quo 

assumptions that additions and retirements are proportional to current water source and 

type of cooling water system. The explanation for this apparent inconsistency is that 

AEO2006 projects capacity retirements primarily from the non-FGD coal and non-coal 

 

Freshwater Needs for Thermoelectric Generation, August 2006 

25 
Figure 12 – Average Daily National Freshwater Consumption for Thermoelectric Power Generation 

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

2005 2010 2015 2020 2025 2030

Year

Daily Consumption (billion gpd)

600

650

700

750

800

850

900

Thermoelectric Generating Capacity (GW)

Case 1

Case 2

Case 3

Case 4

Case 5

Thermoelectric Capacity

fossil generation categories, which have a relatively high proportion of once-through 

cooling systems, while capacity additions are primarily in the FGD coal, IGCC, and 

NGCC generation categories, which have a relatively high proportion of wet recirculating 

cooling systems. In addition, the steam cycle portion of IGCC and NGCC plants is only 

one-third of their total capacity. Since average freshwater withdrawal for once-through 

cooling is significantly higher than wet recirculating cooling – approximately 25 gal/kWh 

versus 0.5 gal/kWh – the net effect is no significant change in overall freshwater 

withdrawal over the next 25 years. 

National freshwater withdrawal for each fuel type in Case 1 is presented in Figure 13. 

The figure shows the relatively unchanged total withdrawal, and the mirroring of 

scrubbed and unscrubbed coal (with scrubbed increasing over time as unscrubbed 

decreases). There is a slight decrease in fossil non-coal withdrawal and a slight increase 

in nuclear withdrawal. 

Total thermoelectric generation freshwater consumption is projected to increase 27% 

from 2005 through 2030 for Case 1 – growing from 6.2 BGD to 7.9 BGD – consistent 

with the increase in generation capacity from 704 GW to 865 GW. Since once-through 

cooling systems have minimal water consumption, the retirement of these systems does 

not have the same effect on national consumption levels as they do on withdrawal levels 

as described above. 

Freshwater Needs for Thermoelectric Generation, August 2006 

26 
Figure 13 - Average Daily National Freshwater Withdrawal by Fuel for Thermoelectric Power 

Generation – Case 1 

National Withdrawal (Case 1)

0.000

20.000

40.000

60.000

80.000

100.000

120.000

140.000

160.000

180.000

2005 2010 2015 2020 2025 2030

Year

Withdrawal (BGD)

Coal Unscrubbed

Coal Scrubbed

Coal w/ & w/out Scrubber

Fossil Non-Coal

Nuclear

Combined Cycle

IGCC

Total

The changes in results over time reveal some interesting trends. Although total water 

withdrawal declines slightly between 2005 and 2030, the decline is not uniform. 

Between 2005 and 2010, in fact, water withdrawal increases from 149.2 BGD to 152.7 

BGD, before falling off to 145.6 BGD by 2015. The initial increase is due to new coal 

and combined-cycle additions (more than 20 GW), while the subsequent decline is due to 

significant retirement of fossil non-coal capacity (more than 35 GW). This difference 

appears in the other cases as well, although to a lesser degree because of competing 

influences unique to each specific case. 

The growing importance of IGCC technology is evident in the results over time. From a 

level of less than 500 MW in 2005, IGCC is expected to account for almost 85 GW by 

2030. While this capacity impact is quite large, the water impact is remarkably small – 

due primarily to the assumption that all new IGCC capacity will be equipped with wet 

recirculating cooling. In 2030, water withdrawal for IGCC is only 0.49 BGD and water 

consumption is 0.374 BGD. 

National freshwater consumption for each fuel type in Case 1 is presented in Figure 14. 

The effects of increased use of NGCC and IGCC can more clearly be seen in the 

consumption graph than in the previous withdrawal graph. Consumption increases for 

each fuel type except unscrubbed coal and fossil non-coal, which decrease. 

Freshwater Needs for Thermoelectric Generation, August 2006 

27 
Figure 14 - Average Daily National Freshwater Consumption by Fuel for Thermoelectric Power 

Generation – Case 1 

National Consumption (Case 1)

0.000

1.000

2.000

3.000

4.000

5.000

6.000

7.000

8.000

9.000

2005 2010 2015 2020 2025 2030

Year

Consumption (BGD)

Coal Unscrubbed

Coal Scrubbed

Coal w/ & w/out Scrubber

Fossil Non-Coal

Nuclear

Combined Cycle

IGCC

Total

Case 2 

Total thermoelectric generation freshwater withdrawal is projected to decrease 

approximately 9% (149.2 BGD to 136.3 BGD) from 2005 through 2030 for Case 2. This 

trend is consistent with the assumptions that all capacity additions use freshwater and wet 

recirculating cooling systems, while capacity retirements are proportional to current 

water source and type of cooling water system. 

Figure 15 displays Case 2 national withdrawal for each fuel type. The decrease in total 

withdrawal can be seen along with a decrease in fossil non-coal and a slight decrease on 

the line representing the combination of scrubbed and unscrubbed coal. Again scrubbed 

coal increases, while unscrubbed decreases. 

Similar to Case 1, total thermoelectric generation freshwater consumption is projected to 

increase – growing 32% from 6.2 BGD to 8.2 BGD between 2005 and 2030 – consistent 

with both the 23% increase in generation capacity and increased use of wet recirculating 

cooling water systems. 

Figure 16 displays Case 2 national consumption for each fuel type. Consumption 

increases are seen in every fuel type except unscrubbed coal and fossil non-coal, which 

decrease. 

Freshwater Needs for Thermoelectric Generation, August 2006 

28 
Figure 15 - Average Daily National Freshwater Withdrawal by Fuel for Thermoelectric Power 

Generation – Case 2 

National Withdrawal (Case 2)

0.000

20.000

40.000

60.000

80.000

100.000

120.000

140.000

160.000

2005 2010 2015 2020 2025 2030

Year

Withdrawal (BGD)

Coal Unscrubbed

Coal Scrubbed

Coal w/ & w/out Scrubber

Fossil Non-Coal

Nuclear

Combined Cycle

IGCC

Total

Case 3 

The Case 3 assumptions are similar to Case 2, except that 90% of capacity additions use 

freshwater and wet recirculating cooling and 10% use saline water with once-through 

cooling. As might be expected, both thermoelectric generation freshwater withdrawal 

and consumption levels for Case 3 are slightly less than the respective values from 

Case 2. In 2030, freshwater withdrawal is 136.3 BGD in Case 2 compared to 136.1 in 

Case 3. Similarly, freshwater consumption in 2030 is 8.2 BGD and 8.1 BGD for Cases 2 

and 3, respectively. 

National freshwater withdrawal for each fuel type in Case 3 is presented in Figure 17. As 

the figure shows, total withdrawal decreases over time. Fossil non-coal and coal 

unscrubbed also display a noticeable decrease. National freshwater consumption for each 

fuel type in Case 3 is presented in Figure 18. Freshwater consumption is shown to 

increase over time. As with previous consumption cases, only coal unscrubbed and fossil 

non-coal consumption decreases from 2005 to 2030. 

Freshwater Needs for Thermoelectric Generation, August 2006 

29 
Figure 16 - Average Daily National Freshwater Consumption by Fuel for Thermoelectric Power 

Generation – Case 2 

National Consumption (Case 2)

0.000

1.000

2.000

3.000

4.000

5.000

6.000

7.000

8.000

9.000

2005 2010 2015 2020 2025 2030

Year

Consumption (BGD)

Coal Unscrubbed

Coal Scrubbed

Coal w/ & w/out Scrubber

Fossil Non-Coal

Nuclear

Combined Cycle

IGCC

Total

Figure 17 - Average Daily National Freshwater Withdrawal by Fuel for Thermoelectric Power 

Generation – Case 3 

National Withdrawal (Case 3)

0.000

20.000

40.000

60.000

80.000

100.000

120.000

140.000

160.000

2005 2010 2015 2020 2025 2030

Year

Withdrawal (BGD) Coal Unscrubbed

Coal Scrubbed

Coal w/ & w/out Scrubber

Fossil Non-Coal

Nuclear

Combined Cycle

IGCC

Total

Freshwater Needs for Thermoelectric Generation, August 2006 

30 
Figure 18 - Average Daily National Freshwater Consumption by Fuel for Thermoelectric Power 

Generation – Case 3 

National Consumption (Case 3)

0.000

1.000

2.000

3.000

4.000

5.000

6.000

7.000

8.000

9.000

2005 2010 2015 2020 2025 2030

Year

Consumption (BGD)

Coal Unscrubbed

Coal Scrubbed

Coal w/ & w/out Scrubber

Fossil Non-Coal

Nuclear

Combined Cycle

IGCC

Total

Case 4 

ential impact of dry cooling systems on water demand is evident in the results of 

igure 19 displays Case 4 national withdrawal for each fuel type. The total freshwater 

The pot

Case 4, where 25% of new capacity is assumed to be equipped with dry cooling, rather 

than wet recirculating cooling. Thermoelectric generation freshwater withdrawal and 

consumption levels for Case 4 are less than the respective values from Case 2. By 2030, 

freshwater withdrawal is projected to be approximately 1% less in Case 4 compared to 

Case 2 – 135.4 BGD vs. 136.3 BGD. More significantly, freshwater consumption is 

projected to be approximately 9% less – 7.5 BGD in Case 4 vs. 8.2 BGD in Case 2. The 

results suggest that dry cooling has the potential to play a significant roll in minimizing 

freshwater consumption in future years if technology is developed to cost effectively 

build and operate dry cooling plants. 

F

withdrawal decreases over time, as does coal unscrubbed, fossil non-coal, and the line 

representing the combination of scrubbed and unscrubbed coal. Figure 20 displays Case 

4 national consumption for each fuel type. Total consumption is shown to increase from 

2005 to 2030, with only coal unscrubbed and fossil non-coal decreasing during that 

period. 

Freshwater Needs for Thermoelectric Generation, August 2006 

31 
Figure 19 - Average Daily National Freshwater Withdrawal by Fuel for Thermoelectric Power 

Generation – Case 4 

National Withdrawal (Case 4)

0.000

20.000

40.000

60.000

80.000

100.000

120.000

140.000

160.000

2005 2010 2015 2020 2025 2030

Year

Withdrawal (BGD)

Coal Unscrubbed

Coal Scrubbed

Coal w/ & w/out Scrubber

Fossil Non-Coal

Nuclear

Combined Cycle

IGCC

Total

Figure 20 - Average Daily National Freshwater Consumption by Fuel for Thermoelectric Power 

Generation – Case 4 

National Consumption (Case 4)

0.000

1.000

2.000

3.000

4.000

5.000

6.000

7.000

8.000

2005 2010 2015 2020 2025 2030

Year

Consumption (BGD)

Coal Unscrubbed

Coal Scrubbed

Coal w/ & w/out Scrubber

Fossil Non-Coal

Nuclear

Combined Cycle

IGCC

Total

Freshwater Needs for Thermoelectric Generation, August 2006 

32 
Case 5 

The Case 5 assumptions for capacity additions and retirements are the same as Case 2. 

However, Case 5 also assumes that 25% of existing freshwater once-through cooling 

capacity is converted to wet recirculating cooling. As a result, Case 5 represents the most 

extreme conditions of the analysis and significantly impacts projections for both 

freshwater withdrawal and consumption. By 2030, total thermoelectric generation 

freshwater withdrawal is projected to be approximately 24% less in Case 5 compared to 

Case 2 – 103.7 BGD vs. 136.3 BGD – while consumption is projected to be 

approximately 12% more – 9.2 BGD in Case 5 vs. 8.2 BGD in Case 2. 

National freshwater withdrawal for each fuel type in Case 5 is presented in Figure 21. 

Total freshwater withdrawal decreases over time, as does withdrawal for all fuel types 

except scrubbed coal (which increases as unscrubbed coal decreases). National 

freshwater consumption for each fuel type in Case 5 is presented in Figure 22. As with 

previous consumption cases, total freshwater consumption increases and unscrubbed coal 

and fossil non-coal are the only fuel types shown to decrease. 

Thermoelectric Generation - Regional

Figures 23-27 show the results of the regional water withdrawal analysis for total U.S. 

thermoelectric generation comparing 2005 to 2030 for each of the five cases. The graphs 

show that aside from Case 1, where the water withdrawal of the SERC region increases, 

the ECAR, SERC, and ERCOT regions experience the largest decreases in water 

withdrawal in each case. Figures 28-32 show the results of the regional water 

consumption analysis for total U.S. thermoelectric generation comparing 2005 to 2030 

for each of the five cases. Inverse to the water withdrawal regional data, the regional 

consumption graphs indicate that the ECAR, SERC, and ERCOT regions, along with the 

western regions WECC/CA, WECC/NWPP, and WECC/RM are all increasing water 

consumption significantly. 

Case 1 

As discussed previously, total thermoelectric generation freshwater withdrawal is 

projected to remain relatively constant from 2005 through 2030 for Case 1 – decreasing 

slightly from 149.2 BGD to 148.4 BGD On a regional basis, freshwater withdrawal 

increases in the MAIN, MAPP, SERC, FRCC, WECC/NW, and WECC/CA regions. 

Decreases occurred in all other regions, with the most significant decreases in the ECAR 

and ERCOT regions (Figure 23). 

Total thermoelectric generation freshwater consumption is projected to increase 27% 

from 2005 through 2030 for Case 1 – growing from 6.2 BGD to 7.9 BGD. Freshwater 

consumption increases in all of the regions, with relatively large percentage increases 

occurring in the NPCC/NY (130%), FRCC (121%), WECC/RM (82%), and WECC/CA 

(298%) regions (Figure 28). 

Freshwater Needs for Thermoelectric Generation, August 2006 

33 
Figure 21 - Average Daily National Freshwater Withdrawal by Fuel for Thermoelectric Power 

Generation – Case 5 

National Withdrawal (Case 5)

0.000

20.000

40.000

60.000

80.000

100.000

120.000

140.000

160.000

2005 2010 2015 2020 2025 2030

Year

Withdrawal (BGD)

Coal Unscrubbed

Coal Scrubbed

Coal w/ & w/out Scrubber

Fossil Non-Coal

Nuclear

Combined Cycle

IGCC

Total

Figure 22 - Average Daily National Freshwater Consumption by Fuel for Thermoelectric Power 

Generation – Case 5 

National Consumption (Case 5)

0.000

1.000

2.000

3.000

4.000

5.000

6.000

7.000

8.000

9.000

10.000

2005 2010 2015 2020 2025 2030

Year

Consumption (BGD)

Coal Unscrubbed

Coal Scrubbed

Coal w/ & w/out Scrubber

Fossil Non-Coal

Nuclear

Combined Cycle

IGCC

Total

Freshwater Needs for Thermoelectric Generation, August 2006 

34 
Figure 23 – Average Daily Regional Freshwater Withdrawal for Thermoelectric Power Generation – 

Case 1 

-10.00

0.00

10.00

20.00

30.00

40.00

50.00

60.00

NPCC/NE

NPCC/NY

ECAR

MAIN

MAAC

MAPP

SERC

FRCC

SPP

ERCOT

WECC/RM

WECC/NWPP

WECC/CA

Withdrawals (BGD)

Water withdrawal, 2005 Incremental water withdrawal, 2005-2030

Case 1

Figure 24 – Average Daily Regional Freshwater Withdrawal for Thermoelectric Power Generation – 

Case 2 

-10.00

0.00

10.00

20.00

30.00

40.00

50.00

NPCC/NE

NPCC/NY

ECAR

MAIN

MAAC

MAPP

SERC

FRCC

SPP

ERCOT

WECC/RM

WECC/NWPP

WECC/CA

Withdrawals (BGD)

Water withdrawal, 2005 Incremental water withdrawal, 2005-2030

Case 2

Freshwater Needs for Thermoelectric Generation, August 2006 

35 
Figure 25 – Average Daily Regional Freshwater Withdrawal for Thermoelectric Power Generation – 

Case 3 

-10.00

0.00

10.00

20.00

30.00

40.00

50.00

NPCC/NE

NPCC/NY

ECAR

MAIN

MAAC

MAPP

SERCFRCC

SPP

ERCOT

WECC/RM

WECC/NWPP

WECC/CA

Withdrawals (BGD)

Water withdrawal, 2005 Incremental water withdrawal, 2005-2030

Case 3

Figure 26 – Average Daily Regional Freshwater Withdrawal for Thermoelectric Power Generation – 

Case 4 

-10.00

0.00

10.00

20.00

30.00

40.00

50.00

NPCC/NE

NPCC/NY

ECAR

MAIN

MAAC

MAPP

SERC

FRCC

SPP

ERCOT

WECC/RM

WECC/NWPP

WECC/CA

Withdrawals (BGD)

Water withdrawal, 2005 Incremental water withdrawal, 2005-2030

Case 4

Freshwater Needs for Thermoelectric Generation, August 2006 

36 
Figure 27 – Average Daily Regional Freshwater Withdrawal for Thermoelectric Power Generation – 

Case 5 

-20.00

-10.00

0.00

10.00

20.00

30.00

40.00

50.00

NPCC/NE

NPCC/NY

ECAR

MAIN

MAAC

MAPP

SERC

FRCC

SPP

ERCOT

WECC/RM

WECC/NWPP

WECC/CA

Withdrawals (BGD)

Water withdrawal, 2005 Incremental water withdrawal, 2005-2030

Case 5

Figure 28 – Average Daily Regional Freshwater Consumption for Thermoelectric Power Generation 

– Case 1 

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

NPCC/NE

NPCC/NY

ECAR

MAIN

MAAC

MAPP

SERC

FRCC

SPP

ERCOT

WECC/RM

WECC/NWPP

WECC/CA

Consumption (BGD)

Water consumption, 2005 Incremental water consumption, 2005-2030

Case 1

Freshwater Needs for Thermoelectric Generation, August 2006 

37 
Figure 29 – Average Daily Regional Freshwater Consumption for Thermoelectric Power Generation 

– Case 2 

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

NPCC/NE

NPCC/NY

ECAR

MAIN

MAAC

MAPP

SERC

FRCC

SPP

ERCOT

WECC/RM

WECC/NWPP

WECC/CA

Consumption (BGD)

Water consumption, 2005 Incremental water consumption, 2005-2030

Case 2

Figure 30 – Average Daily Regional Freshwater Consumption for Thermoelectric Power Generation 

– Case 3 

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

NPCC/NE

NPCC/NY

ECAR

MAIN

MAAC

MAPP

SERC

FRCC

SPP

ERCOT

WECC/RM

WECC/NWPP

WECC/CA

Consumption (BGD)

Water consumption, 2005 Incremental water consumption, 2005-2030

Case 3

Freshwater Needs for Thermoelectric Generation, August 2006 

38 
Figure 31 – Average Daily Regional Freshwater Consumption for Thermoelectric Power Generation 

– Case 4 

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

NPCC/NE

NPCC/NY

ECAR

MAIN

MAAC

MAPP

SERC

FRCC

SPP

ERCOT

WECC/RM

WECC/NWPP

WECC/CA

Consumption (BGD)

Water consumption, 2005 Incremental water consumption, 2005-2030

Case 4

Figure 32 – Average Daily Regional Freshwater Consumption for Thermoelectric Power Generation 

– Case 5 

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

NPCC/NE

NPCC/NY

ECAR

MAIN

MAAC

MAPP

SERC

FRCC

SPP

ERCOT

WECC/RM

WECC/NWPP

WECC/CA

Consumption (BGD)

Water consumption, 2005 Incremental water consumption, 2005-2030

Case 5

Freshwater Needs for Thermoelectric Generation, August 2006 

39 
Case 2 

Total thermoelectric generation freshwater withdrawal is projected to decrease 

approximately 9% (149.2 BGD to 136.3 BGD) from 2005 through 2030 for Case 2. 

Similar to Case 1, total thermoelectric generation freshwater consumption is projected to 

increase – growing 32% from 6.2 BGD to 8.2 BGD between 2005 and 2030. On a 

regional basis, freshwater withdrawal increases slightly in the FRCC and WECC/NWPP 

regions; and decreases significantly in the ECAR, SERC, and ERCOT regions 

(Figure 24). Similar to Case 1, freshwater consumption increases in all of the regions, 

with relatively large percentage increases occurring in the NPCC/NY (132%), FRCC 

(199%), WECC/RM (74%), and WECC/CA (352%) regions (Figure 29). 

Case 3 

Both thermoelectric generation freshwater withdrawal and consumption levels for Case 3 

are slightly less than the respective values from Case 2. In 2030, freshwater withdrawal 

is 136.3 BGD in Case 2 compared to 136.1 in Case 3. Similarly, freshwater consumption 

in 2030 is 8.2 BGD and 8.1 BGD for Cases 2 and 3, respectively. On a regional basis, 

freshwater withdrawal and consumption increases and decreases are also similar to 

Case 2 (Figure 25 and Figure 30). 

Case 4 

Thermoelectric generation freshwater withdrawal and consumption levels for Case 4 are 

less than the respective values from Case 2. By 2030, freshwater withdrawal is projected 

to be approximately 1% less in Case 4 compared to Case 2 – 135.4 BGD vs. 136.3 BGD. 

More significantly, freshwater consumption is projected to be approximately 9% less – 

7.5 BGD in Case 4 vs. 8.2 BGD in Case 2. On a regional basis, freshwater withdrawal 

and consumption increases and decreases are also similar to Case 2 (Figure 26 and 

Figure 31). 

Case 5 

The Case 5 assumptions for capacity additions and retirements are the same as Case 2, 

but Case 5 also assumes that 25% of existing freshwater once-through cooling capacity is 

converted to wet recirculating cooling. By 2030, total thermoelectric generation 

freshwater withdrawal is projected to be approximately 24% less in Case 5 compared to 

Case 2 – 103.7 BGD vs. 136.3 BGD – while consumption is projected to be 

approximately 12% more – 9.2 BGD in Case 5 vs. 8.2 BGD in Case 2. On a regional 

basis, freshwater withdrawal increases in the FRCC (9%) and WECC/NWPP (21%) 

regions; and decreases in all other regions, with significant decreases in the NPCC/NY 

(24%), ECAR (48%), MAIN (19%), MAAC (21%), MAPP (25%), SERC (23%), SPP 

(23%), ERCOT (43%), and WECC/RM (39%) regions (Figure 27). Freshwater 

consumption increases in all of the regions, with relatively large percentage increases 

occurring in the NPCC/NE (72%), NPCC/NY (271%), ECAR (56%), SERC (49%), 

FRCC (231%), WECC/RM (74%), and WECC/CA (356%) regions (Figure 32). 

Freshwater Needs for Thermoelectric Generation, August 2006 

40 
Coal-Fired Generation - National

Coal-fired generating capacity is projected to increase by 148 GW from 2005 to 2030. 

The analysis projects that by 2030, average daily national freshwater withdrawals 

required to meet the needs of the U.S. coal-fired generation component of thermoelectric 

generation may decrease to 66.0 BGD (28%) or increase to 98.2 BGD (7%) depending 

upon case assumptions. Table 10 presents the range of average daily national freshwater 

withdrawal for each of the five cases from 2005 through 2030. This same data is 

presented graphically in Figure 33. 

Table 10 –Average National Freshwater Withdrawal for Coal-Fired Power Generation (BGD) 

 2005 2010 2015 2020 2025 2030 

Case 1 91.7 94.9 94.1 95.4 97.0 98.2 

Case 2 91.6 91.6 90.4 89.4 89.1 89.0 

Case 3 91.6 91.6 90.4 89.3 89.0 88.9 

Case 4 91.6 91.5 90.3 89.2 88.9 88.6 

Case 5 91.6 82.3 76.7 71.3 68.6 66.0 

Maximum 91.7 94.9 94.1 95.4 97.0 98.2 

Minimum 91.6 82.3 76.7 71.3 68.6 66.0 

Figure 33 –Average Daily National Freshwater Withdrawal for Coal-Fired Power Generation 

0.0

20.0

40.0

60.0

80.0

100.0

120.0

2005 2010 2015 2020 2025 2030

Year

Daily Withdrawals (billion gpd)

250

300

350

400

450

500

Case 1

Coal-Fired Generating Capacity (GW)

Case 2

Case 3

Case 4

Case 5

Coal-Fired Capacity

The analysis projects that by 2030, average daily national freshwater consumption 

resulting from U.S. coal-fired power generation could range from 3.4 BGD to 4.0 BGD 

depending upon case assumptions. This represents an increase of 48% and 74% 

Freshwater Needs for Thermoelectric Generation, August 2006 

41 
respectively. Table 11 presents the range of average daily national freshwater 

consumption for each of the five cases from 2005 through 2030. This same data is 

presented graphically in Figure 34. 

Table 11 – Average National Freshwater Consumption for Coal-Fired Power Generation (BGD) 

 2005 2010 2015 2020 2025 2030 

Case 1 2.3 2.6 2.6 2.9 3.2 3.6 

Case 2 2.3 2.6 2.7 2.9 3.3 3.7 

Case 3 2.3 2.6 2.7 2.9 3.2 3.6 

Case 4 2.3 2.6 2.6 2.8 3.1 3.4 

Case 5 2.3 2.8 2.9 3.2 3.6 4.0 

Maximum 2.3 2.8 2.9 3.2 3.6 4.0 

Minimum 2.3 2.6 2.6 2.8 3.1 3.4 

Figure 34 – Average Daily National Freshwater Consumption for Coal-Fired Power Generation 

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

2005 2010 2015 2020 2025 2030

Year

Daily Consumption (billion gpd)

250

300

350

400

450

500

Coal-Fired Generating Capacity (GW)

Case 1

Case 2

Case 3

Case 4

Case 5

Coal-Fired Capacity

National Conventional Coal Results 

Case 1 

The conventional coal (not including IGCC) portion of thermoelectric generation 

freshwater withdrawal is projected to increase approximately 7% from 2005 through 

2030 for Case 1 – from 91.7 BGD to 97.7 BGD – consistent with the overall 18% 

increase in generation capacity from 309 GW to 366 GW and roughly equal distribution 

of once-through and wet recirculating cooling water systems. More significantly, 

Freshwater Needs for Thermoelectric Generation, August 2006 

42 
conventional coal generation freshwater consumption is projected to increase 39% from 

2005 through 2030 for Case 1 – growing from 2.3 BGD to 3.2 BGD. See Figure 13 and 

Figure 14 for plots of coal withdrawal and consumption from 2005-2030. 

Case 2 

Conventional coal generation freshwater withdrawal is projected to decrease 

approximately 3% (91.6 BGD to 88.5 BGD) from 2005 through 2030 for Case 2. This 

trend is consistent with the assumptions that all capacity additions use freshwater and wet 

recirculating cooling systems, while capacity retirements are proportional to current 

water source and type of cooling water system. 

Similar to Case 1, conventional coal generation freshwater consumption is projected to 

increase in Case 2 – growing 43% from 2.3 BGD to 3.3 BGD between 2005 and 2030 – 

consistent with both the 18% increase in generation capacity and increased use of wet 

recirculating cooling water systems. See Figure 15 and Figure 16 for plots of coal 

withdrawal and consumption from 2005-2030. 

Case 3 

The Case 3 assumptions are similar to Case 2, except that 90% of capacity additions use 

freshwater and wet recirculating cooling and 10% use saline water with once-through 

cooling. As might be expected, both conventional coal generation freshwater withdrawal 

and consumption levels for Case 3 are slightly less than the respective values from 

Case 2. In 2030, freshwater withdrawal is 88.5 BGD in Case 2 compared to 88.4 in 

Case 3. Similarly, freshwater consumption in 2030 is 3.3 BGD and 3.2 BGD for Cases 2 

and 3, respectively. See Figure 17 and Figure 18 for plots of coal withdrawal and 

consumption from 2005-2030. 

Case 4 

The potential impact of dry cooling systems on water demand is evident in the results of 

Case 4, where 25% of new conventional coal capacity is assumed to be equipped with dry 

cooling, rather than wet recirculating cooling. Conventional coal generation freshwater 

withdrawal and consumption levels for Case 4 are less than the respective values from 

Case 2. By 2030, freshwater withdrawal is projected to be slightly less in Case 4 

compared to Case 2 – 88.3 BGD vs. 88.5 BGD. Freshwater consumption is projected to 

be approximately 6% less – 3.1 BGD in Case 4 vs. 3.3 BGD in Case 2. See Figure 19 

and Figure 20 for plots of coal withdrawal and consumption from 2005-2030. 

Case 5 

The Case 5 assumptions for conventional coal capacity additions and retirements are the 

same as Case 2. However, Case 5 also assumes that 25% of existing freshwater oncethrough cooling capacity is converted to wet recirculating cooling. As a result, Case 5 

represents the most extreme conditions of the analysis and significantly impacts 

projections for both freshwater withdrawal and consumption. By 2030, total 

conventional coal generation freshwater withdrawal is projected to be approximately 26% 

less in Case 5 compared to Case 2 – 65.5 BGD vs. 88.5 BGD – while consumption is 

Freshwater Needs for Thermoelectric Generation, August 2006 

43 
projected to be approximately 12% more – 3.7 BGD in Case 5 vs. 3.3 BGD in Case 2. 

See Figure 21 and Figure 22 for plots of coal withdrawal and consumption from 2005-

2030. 

Coal-Fired Generation - Regional 

Figures 35-39 shows the results of the regional water withdrawal analysis for total U.S. 

coal-fired generation comparing 2005 to 2030 for each of the five cases. With each 

successive case, the water withdrawal of the regions displays greater decreases, with Case 

5 showing the largest overall decrease in water withdrawal. Figures 40-44 show the 

results of the regional water consumption analysis for total U.S. coal-fired generation 

comparing 2005 to 2030 for each of the five cases. Aside from Case 5, where water 

consumption increases more than other cases, the water consumption regionally stays 

rather consistent. 

Case 1 

Conventional coal generation freshwater withdrawal is projected to increase 

approximately 7% from 2005 through 2030 for Case 1 – from 91.7 BGD to 97.7 BGD. 

Conventional coal freshwater consumption is projected to increase 39% from 2005 

through 2030 for Case 1 – growing from 2.3 BGD to 3.2 BGD. On a regional basis, 

freshwater withdrawal increases in the MAIN, SERC, FRCC, SPP, ERCOT, WECC/RM, 

and WECC/CA regions; and decreases in the NPCC/NE (3%), NPCC/NY (1%), and 

ECAR (3%) regions (Figure 35). Freshwater consumption increases in all of the regions, 

with relatively large percentage increases occurring in the NPCC/NE (1,000%), 

NPCC/NY (587%), FRCC (173%), WECC/RM (132%), and WECC/CA (540%) regions 

(Figure 40). 

Case 2 

Conventional coal generation freshwater withdrawal is projected to decrease 

approximately 3% (91.6 BGD to 88.5 BGD) from 2005 through 2030 for Case 2. Similar 

to Case 1, conventional coal generation freshwater consumption is projected to increase 

in Case 2 – growing 43% from 2.3 BGD to 3.3 BGD between 2005 and 2030. On a 

regional basis, freshwater withdrawal increases slightly in the FRCC, WECC/RM, 

WECC/NWPP, and WECC/CA regions; and decreases slightly in the ECAR, MAIN, 

MAPP, SERC, and SPP regions (Figure 36). Similar to Case 1, freshwater consumption 

increases in all of the regions, with relatively large percentage increases occurring in the 

NPCC/NE (1,000%), NPCC/NY (587%), MAIN (86%), FRCC (298%), ERCOT (88%), 

WECC/RM (120%), WECC/NWPP (81%), and WECC/CA (665%) regions (Figure 41). 

Case 3 

Both conventional coal generation freshwater withdrawal and consumption levels for 

Case 3 are slightly less than the respective values from Case 2. In 2030, freshwater 

withdrawal is 88.5 BGD in Case 2 compared to 88.4 in Case 3 (Figure 37). Similarly, 

freshwater consumption in 2030 is 3.3 BGD and 3.2 BGD for Cases 2 and 3, respectively 

(Figure 42). On a regional basis, freshwater withdrawal and consumption increases and 

decreases are also similar to Case 2. 

Freshwater Needs for Thermoelectric Generation, August 2006 

44 
Figure 35 – Average Daily Regional Freshwater Withdrawal for Coal-Fired Power Generation – 

Case 1 

-5.00

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

NPCC/NE

NPCC/NY

ECAR

MAIN

MAAC

MAPP

SERC

FRCC

SPP

ERCOT

WECC/RM

WECC/NWPP

WECC/CA

Withdrawals (BGD)

Water withdrawal, 2005 Incremental water withdrawal, 2005-2030

Case 1

Figure 36 – Average Daily Regional Freshwater Withdrawal for Coal-Fired Power Generation – 

Case 2 

-5.00

0.00

5.00

10.00

15.00

20.00

25.00

30.00

NPCC/NE

NPCC/NY

ECAR

MAIN

MAAC

MAPP

SERC

FRCC

SPP

ERCOT

WECC/RM

WECC/NWPP

WECC/CA

Withdrawals (BGD)

Water withdrawal, 2005 Incremental water withdrawal, 2005-2030

Case 2

Freshwater Needs for Thermoelectric Generation, August 2006 

45 
Figure 37 – Average Daily Regional Freshwater Withdrawal for Coal-Fired Power Generation – 

Case 3 

-5.00

0.00

5.00

10.00

15.00

20.00

25.00

30.00

NPCC/NE

NPCC/NY

ECAR

MAIN

MAAC

MAPP

SERC

FRCC

SPP

ERCOT

WECC/RM

WECC/NWPP

WECC/CA

Withdrawals (BGD)

Water withdrawal, 2005 Incremental water withdrawal, 2005-2030

Case 3

Figure 38 – Average Daily Regional Freshwater Withdrawal for Coal-Fired Power Generation – 

Case 4 

-10.00

-5.00

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

NPCC/NE

NPCC/NY

ECAR

MAIN

MAAC

MAPP

SERC

FRCC

SPP

ERCOT

WECC/RM

WECC/NWPP

WECC/CA

Withdrawals (BGD)

Water withdrawal, 2005 Incremental water withdrawal, 2005-2030

Case 4

Freshwater Needs for Thermoelectric Generation, August 2006 

46 
Figure 39 – Average Daily Regional Freshwater Withdrawal for Coal-Fired Power Generation – 

Case 5 

-20.00

-15.00

-10.00

-5.00

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

NPCC/NE

NPCC/NY

ECAR

MAIN

MAAC

MAPP

SERCFRCC

SPP

ERCOT

WECC/RM

WECC/NWPP

WECC/CA

Withdrawals (BGD)

Water withdrawal, 2005 Incremental water withdrawal, 2005-2030

Case 5

Figure 40 – Average Daily Regional Freshwater Consumption for Coal-Fired Power Generation – 

Case 1 

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

NPCC/NE

NPCC/NY

ECAR

MAIN

MAAC

MAPP

SERC

FRCC

SPP

ERCOT

WECC/RM

WECC/NWPP

WECC/CA

Consumption (BGD)

Water consumption, 2005 Incremental water consumption, 2005-2030

Case 1

Freshwater Needs for Thermoelectric Generation, August 2006 

47 
Figure 41 – Average Daily Regional Freshwater Consumption for Coal-Fired Power Generation – 

Case 2 

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

NPCC/NE

NPCC/NY

ECAR

MAIN

MAAC

MAPP

SERC

FRCC

SPP

ERCOT

WECC/RM

WECC/NWPP

WECC/CA

Consumption (BGD)

Water consumption, 2005 Incremental water consumption, 2005-2030

Case 2

Figure 42 – Average Daily Regional Freshwater Consumption for Coal-Fired Power Generation – 

Case 3 

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

NPCC/NE

NPCC/NY

ECAR

MAIN

MAAC

MAPP

SERC

FRCC

SPP

ERCOT

WECC/RM

WECC/NWPP

WECC/CA

Consumption (BGD)

Water consumption, 2005 Incremental water consumption, 2005-2030

Case 3

Freshwater Needs for Thermoelectric Generation, August 2006 

48 
Figure 43 – Average Daily Regional Freshwater Consumption for Coal-Fired Power Generation – 

Case 4 

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

NPCC/NE

NPCC/NY

ECAR

MAIN

MAAC

MAPP

SERC

FRCC

SPP

ERCOT

WECC/RM

WECC/NWPP

WECC/CA

Consumption (BGD)

Water consumption, 2005 Incremental water consumption, 2005-2030

Case 4

Figure 44 – Average Daily Regional Freshwater Consumption for Coal-Fired Power Generation – 

Case 5 

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

NPCC/NE

NPCC/NY

ECAR

MAIN

MAAC

MAPP

SERC

FRCC

SPP

ERCOT

WECC/RM

WECC/NWPP

WECC/CA

Consumption (BGD)

Water consumption, 2005 Incremental water consumption, 2005-2030

Case 5

Freshwater Needs for Thermoelectric Generation, August 2006 

49 
Case 4 

Conventional coal generation freshwater withdrawal and consumption levels for Case 4 

are less than the respective values from Case 2. By 2030, freshwater withdrawal is 

projected to be slightly less in Case 4 compared to Case 2 – 88.3 BGD vs. 88.5 BGD 

(Figure 38). Freshwater consumption is projected to be approximately 6% less – 3.1 

BGD in Case 4 vs. 3.3 BGD in Case 2 (Figure 43). On a regional basis, freshwater 

withdrawal and consumption increases and decreases are also similar to Case 2. 

Case 5 

By 2030, total conventional coal generation freshwater withdrawal is projected to be 

approximately 26% less in Case 5 compared to Case 2 – 65.5 BGD vs. 88.5 BGD – while 

consumption is projected to be approximately 12% more – 3.7 BGD in Case 5 vs. 3.3 

BGD in Case 2. On a regional basis, freshwater withdrawal increases in the WECC/RM 

(113%) region; and decreases significantly in the NPCC/NY (22%), ECAR (45%), 

MAIN (18%), MAAC (21%), MAPP (25%), SERC (24%), SPP (16%), and ERCOT 

(18%) regions (Figure 39). Freshwater consumption increases in all of the regions, with 

relatively large percentage increases occurring in the NPCC/NE (1,136%), NPCC/NY 

(838%), ECAR (53%), MAIN (120%), SERC (56%), FRCC (352%), ERCOT (115%), 

WECC/RM (120%), WECC/NWPP (81%), and WECC/CA (669%) regions (Figure 44). 

Comparison of 2004 & 2006 study projections 

Comparing the results of the 2004 water needs analysis with the results of the updated 

2006 water needs analysis must begin with a discussion of the different methodologies 

used for each analysis. Because the two studies used fundamentally different analytical 

approaches, the results must be examined in terms of general agreement and consistent 

trends, not in terms of close numerical similarity. 

As a broad generalization of the two methodologies employed, the 2004 study provided a 

top-down analysis, while the 2006 study provided a bottoms-up analysis. The 2004 

analysis used as its starting point the thermoelectric water withdrawal estimated by the 

U.S. Geologic Survey in its 1995 survey. In other words, the estimated total 

thermoelectric withdrawal, 132.1 BGD, represented the baseline withdrawal for all six 

cases considered (a description of the cases used in the 2004 analysis can be found in the 

Introduction section of this paper). Changes in withdrawal and consumption over time 

were calculated from this base for each case using the capacity additions and retirements 

projected by the Annual Energy Outlook 2004 out to 2025; single-point national average 

withdrawal and consumption factors for fossil and nuclear power plants (recirculating 

and once-through); and AEO 2004’s capacity factor projections. 

The 2006 analysis, on the other hand, used as its starting point the water withdrawal and 

consumption quantities associated with specific power plant configurations in a particular 

region. In other words, water withdrawal and consumption factors were calculated from 

plant data (see Table 5 for data sources) for a number of different power plant types; 

these factors were then applied to the capacity of each plant type in each region to 

calculate regional water withdrawal and consumption amounts. The regional quantities 

could be summed to assess national impacts. Changes in withdrawal and consumption 

Freshwater Needs for Thermoelectric Generation, August 2006 

50 
over time were calculated for each case using the capacity additions and retirements 

projected by the Annual Energy Outlook 2006 out to 2030; the plant type-specific and 

region-specific withdrawal and consumption factors described above; and AEO 2006’s 

capacity factor projections. 

Although the 2004 water needs analyses evaluated six cases, and the 2006 water needs 

analysis evaluated five cases, only one was the same (Case 2 in the 2004 analysis and 

Case 1 in the 2006 analysis), in which additions and retirements are proportional to 

current source withdrawals. Table 12 presents the results of these two cases over 

equivalent 25-year periods. For the 2004 analysis, the baseline thermoelectric water 

withdrawal, as noted above, was 132.1 BGD in 1995. For the 2006 analysis, the baseline 

thermoelectric water withdrawal was 149.2 BGD in 2005. The 13% difference in the 

baseline estimate is relatively small considering the 10-year time lag and the difference in 

the analytical methodologies between the two studies. As another point of comparison, 

USGS estimated thermoelectric water withdrawal for the year 2000 as 136 BGD, 

indicating a 3% increase in water withdrawal from 1995 to 2000. Extrapolating this 3% 

increase to 2005 results in a thermoelectric water withdrawal estimate of 140 BGD in 

2005, or about 6% less than the 2005 withdrawal value calculated in the 2006 analysis. It 

should be pointed out, however, that about 200 GW of new capacity came on-line 

between 2000 and 2005 – a large fraction of which was combined-cycle capacity. 

Combined-cycle plants have lower water requirements than conventional fossil steam 

plants because only about one-third of the plant capacity operates on the Rankine steam 

cycle, but the water requirements are not insignificant, particularly across 100+ GW. 

Table 12 - Results Comparison, 2004 vs. 2006 Water Needs Analysis 

Year 1995 2001 2002 2005 2010 2015 2020 2025 2030 

Withdrawal 

(BGD) 

132.1 131.3 131.4 123.6 123.5 123.3 123.1 2004 

Analysis, 

Case 2 Consumption 

(BGD) 

3.3 3.6 3.9 4.7 5.4 6.1 7.1 

Withdrawal 

(BGD) 

149.2 152.7 145.6 147.6 148.8 148.4 2006 

Analysis, 

Case 1 Consumption 

(BGD) 

6.2 6.6 6.8 7.3 7.6 7.9 

Case 2 from the 2004 analysis projected a 6.6% decline in water withdrawal over a 25-

year period from 1995 to 2020, from 132.1 BGD to 123.3 BGD. The corresponding 

Case 1 from the 2006 analysis projected a 0.5% decline in water withdrawal over a 25-

year period from 2005 to 2030, from 149.2 BGD to 148.4 BGD. The 2004 study reports 

a much larger decline in withdrawal because all retirements in the 2004 analysis are 

assumed to be from plants equipped with once-through cooling systems (with their higher 

water withdrawal requirements), while the 2006 analysis assumes retirements are divided 

among once-through and recirculating systems according to their relative percentage in 

2005. 

In terms of consumption, comparing values between the 2004 and 2006 analyses is less 

meaningful than comparing trends. The baseline thermoelectric consumption from the 

Freshwater Needs for Thermoelectric Generation, August 2006 

51 
2004 water needs analysis, 3.3 BGD, came from USGS’s 1995 estimate, and equals 2.5% 

of withdrawal. For the 2006 analysis, consumption was computed from the individual 

plant and regional calculations. The baseline thermoelectric water consumption for Case 

1 in the 2006 analysis was 6.2 BGD, which represents about 4% of withdrawal. 

Consumption trends across equivalent 25-year time periods are in the same direction and 

of similar magnitude between the 2004 and 2006 analyses. Case 2 of the 2004 water 

needs analysis projected an increase in consumption from 1995 to 2020 of 85%, from 3.3 

BGD to 6.1 BGD. Case 1 of the 2006 water needs analysis projected an increase in 

consumption from 2005 to 2030 of 27%, from 6.2 BGD to 7.9 BGD. The greater 

numerical increase in consumption for the 2004 analysis is due to the 2004 assumption 

that all new plants would use freshwater recirculating systems and to the higher water 

consumption factors used for recirculating systems. 

Conclusions

Population shifts, increasing power demand, and greater competition for water resources 

has heightened interest in the link between energy and water. The EIA projects about a 

24% increase in total generating capacity by 2030 compared to 2005. Of the 312 GW of 

new capacity, more than 233 GW will be thermoelectric generation. 

On a national basis, this analysis indicates that the potential impacts on future freshwater 

withdrawals to meet forecasted increases in electricity generating capacity would be 

relatively low, with most cases exhibiting a decrease in daily withdrawals. The national 

freshwater withdrawal requirements to operate the 233 GW of new thermoelectric 

generating capacity in 2030 will range from a 1% to a 30% decrease compared to 

freshwater withdrawals in 2005. Conversely, many of the cases project a significant 

increase in freshwater consumption by 2030 on a percentage basis. Changes in 

freshwater consumption in 2030 will range from a 21% to as much as a 48% increase 

compared to 2005. Similar trends in freshwater withdrawal and consumption are 

projected for the additional coal-based generating capacity that will come on line by 

2030, with withdrawal ranging from a 28% decrease to a 7% increase and consumption 

ranging from a 48% to a 74% increase. 

The regional component of the 2006 water needs analysis revealed some significant 

differences from the national averages, reflecting recent U.S. population shifts. Regions 

with strong population growth, such as the southeast and southwest, exhibit high growth 

in water consumption requirements, while regions with minimal to modest population 

growth, such as the midwest and mid-Atlantic, exhibit modest growth in water 

consumption requirements. EIA projects a 66% increase in thermoelectric capacity by 

2030 for the western United States and a 61% increase in the southeast compared to the 

24% increase nationally. These increases in projected capacity will occur in regions of 

the United States that are challenged in terms of both current and future availability of 

freshwater. For example, consider Case 2, a plausible future cooling system scenario that 

assumes all capacity additions use freshwater and wet recirculating cooling. The national 

percent changes indicate that water withdrawal will fall by 8.6% and that water 

Freshwater Needs for Thermoelectric Generation, August 2006 

52 
consumption will rise by 32.3% between 2005 and 2030. On a regional basis, however, 

water withdrawal ranges from a 25% increase in Florida to a 30% decline in Texas; and 

while freshwater consumption increases in all regions, the biggest gains come in 

California (352%), Florida (199%), New York (132%) and the Rocky Mountain/desert 

southwest region (74%). 

The thermoelectric power generation sector will remain a significant water consumer for 

the foreseeable future. While national water withdrawals are projected to decline slightly 

over the 25-year time period evaluated in this analysis, the amount of water withdrawal is 

huge, on the order of 135 to 140 billion gallons per day. On a consumption basis, 

although the magnitude is much less than that for withdrawal, the trend is steadily 

upward, regardless of the case considered. National water consumption is expected to 

grow from 6.2 billion gallons per day in 2005 to 8 or 9 billion gallons per day by 2030. 

In the face of growing competition for water resources – particularly in the arid West and 

Southwest, and in the expanding Southeast – regional and national efforts to reduce water 

withdrawal and consumption for thermoelectric power plants are expected to intensify. 

Freshwater Needs for Thermoelectric Generation, August 2006 

53 
Appendix A 

Energy-Water Issues 

Supplemental Information

Water Availability

In 2006, RDS contacted state government water monitoring agencies inquiring if water 

availability in general is a concern in their state. Of the 33 states that responded, 58% of 

states said that yes, water availability is a concern. An additional 15% said that water 

availability varies within the state, with only some regions having water supply issues. 

Another 12% responded that water availability had not been of great concern in the past, 

but has recently been becoming more critical. 

Water availability issues are not limited to the western United States. State government 

water monitoring contacts in Alabama, Florida, Hawaii, Illinois, Louisiana, Missouri, 

South Carolina, and Virginia indicated that water availability is generally a concern in 

their state or has become more of a concern in recent years. A February 2006 article in 

the Baltimore Sun14 describes the difficulties of several communities in Maryland facing 

water shortages, where “growing towns in Carroll and Frederick counties have been 

forced to curtail development – either voluntarily or under orders from the state – because 

their growth was outstripping water supplies.” In addition, the article states that in 

“Southern Maryland, the state’s fastest-growing region, groundwater levels are dropping 

an average of 1 to 2 feet a year.” 

Competing Water Uses

Concerns over limited water quantities are not restricted to thermoelectric generation. 

According to USGS, 346 billion gallons of freshwater were withdrawn per day in the 

United States in the year 2000.4 The largest use, agricultural irrigation, accounted for 

40% of freshwater withdrawn (see Figure A-1). 

Figure A-1 - Percent of freshwater withdrawal by use category 

U.S. Freshwater Withdrawal (2000)

Thermoelectric, 39%

Public Supply, 13% Domestic, 1%

Irrigation, 40%

Livestock, 1%

Aquaculture, 1%

Industrial, 5%

Mining, 1%

Freshwater Needs for Thermoelectric Generation, August 2006 

A-1 
The second largest use, thermoelectric generation, withdrew 136 billion gallons per day 

(BGD), followed by public supply, industrial uses, aquaculture, domestic use, mining, 

and livestock. Interestingly, thermoelectric generation withdrew the largest amount of 

saline water, 60 BGD (96% of all saline withdrawn). Withdrawal of saline water (and 

other non-traditional waters) reduces the strain on freshwater supplies and is one research 

area facilitated by the IEP program.

USGS estimates for freshwater consumption for the year 1995 (the most recent year for 

which this data is available) is presented in Figure A-2.5 Freshwater consumption for 

thermoelectric purposes appears low (only 3%) when compared to other use categories 

(irrigation was responsible for 81% of water consumed). However, even at 3% 

consumption, over 3 BGD were consumed. As a result of growing public pressures to 

withdraw less water, coupled with requirements under Section 316(b) of the Clean Water 

Act, consumption will likely increase significantly due to greater use of closed-loop 

cooling systems that consumes far more water than once-through cooling systems due to 

evaporation losses. 

Figure A-2 - Percent of freshwater consumption by use category

U.S. Freshwater Consumption (1995)

Thermoelectric, 3%

Mining, 1%

Industrial, 3%

Livestock, 3%

Irrigation, 81%

Domestic, 6%

Commercial, 1%

In addition to the water uses described above, increased value is being placed on instream freshwater uses, consisting mainly of habitat/species protection and recreational 

uses. In-stream uses will require a minimum flow rate or depth to be maintained in water 

bodies. 

Because freshwater supply is limited, choices will have to be made regarding withdrawal 

and consumption of this natural resource. Water availability and its withdrawal and 

consumption are top priorities on the public agenda in many nations throughout the 

world. It is likely that the issue will also filter to the top of the U.S. public agenda in the 

near future. In water-stressed areas of the country, power plants will increasingly 

compete with other water users. Agriculture and public supply will most likely be the 

greatest competitors due to their large water withdrawal. As with all resources, tradeoffs 

will occur, and concerns will increasingly be raised over which use is more important: 

water for drinking and personal use, growing food, or energy production. 

Freshwater Needs for Thermoelectric Generation, August 2006 

A-2 
Regulatory Impacts on Water Withdrawal and Consumption

The power industry must comply with a variety of local, state and federal regulations 

pertaining to water acquisition, use, and quality. In considering long-term water 

withdrawal and consumption patterns in the power sector, the cooling water intake 

structure regulations established under the Clean Water Act, Section 316(b) will likely 

have the greatest impact. Designed to protect aquatic life from inadvertently being killed 

by intake structures at power stations and certain manufacturing facilities, Section 316(b) 

requires EPA to ensure that the “location, design, construction and capacity of cooling 

water intake structures reflect the best technology available for minimizing adverse 

environmental impact.” 

EPA divided its 316(b) rulemaking into three phases: Phase I, completed in late 2001, 

applies to new facilities; Phase II, completed in early 2004, applies to large existing 

power facilities; and Phase III, due to be finalized in 2006, applies to existing 

manufacturing facilities. The regulations establish performance standards for cooling 

water intake structures based on impingement mortality and entrainment (IM&E) 

impacts. A minimum level of IM&E reduction is required based on the type of water 

body a given facility accesses for cooling water. Compliance with 316(b) is coordinated 

through the individual states’ NPDES (National Pollutant Discharge Elimination System) 

permitting program. 

The largest design impact of 316(b) compliance is that most new power plants will have 

to use closed-loop, recirculating cooling systems or dry (air-cooled) systems. Open-loop 

systems are strongly discouraged unless the permit applicant can demonstrate that 

alternative IM&E measures can provide a reduction level comparable to that achieved 

through closed-loop cooling or that the compliance costs, air quality impacts, and/or 

energy generation impacts would outweigh the IM&E benefits and justify an open-loop 

system. Because 316(b) portends a greater reliance on closed-loop cooling systems, 

water withdrawal and consumption patterns for the thermoelectric power sector are 

destined to change over time. Even accounting for significant thermoelectric capacity 

additions, water withdrawal levels will likely remain relatively constant. Water 

consumption, on the other hand, is expected to increase substantially since closed-loop 

cooling systems consume more water, due to evaporation, than open-loop systems. 

Existing and future air quality regulations will also affect water withdrawal and 

consumption patterns, although to a lesser extent than cooling water regulations. Tighter 

emission levels for sulfur dioxide, for example, have sparked a mini-boom in the flue gas 

desulfurization (FGD) market. The size of the U.S. FGD market is expected to increase 

by more than 100,000 megawatts (MW) over the next 10 years. Although FGD water 

requirements are a fraction of those required for cooling purposes, FGD units require a 

significant amount of water to produce and handle the various process streams (limestone 

slurry, scrubber sludge, etc.). Makeup water requirements for the FGD island at a 

nominal 550 MW subcritical coal-fired power plant are about 570 gpm, versus about 

9,500 gpm for cooling water makeup.15 Nonetheless, the additional FGD systems 

coming online within the next decade will place a greater strain on water supplies. 

Freshwater Needs for Thermoelectric Generation, August 2006 

A-3 
Notably, semi-dry flue gas desulfurization systems are available that substantially reduce 

water requirements for SO2 control, and these systems are in commercial application at 

numerous plants, many in arid environments. 

Several other regulatory actions warrant attention because of their potential impact on 

water withdrawal and consumption. Under section 303(d) of the 1972 Clean Water Act, 

states, territories, and authorized tribes are required to develop a list of impaired waters 

not meeting water quality standards and then establish total maximum daily loads 

(TMDL) for these waters. A TMDL specifies the maximum amount of a pollutant that a 

waterbody can receive and still meet water quality standards, and allocates pollutant 

loadings among point and nonpoint pollutant sources. TMDL requirements could 

potentially constrain a power plant’s ability to discharge cooling water, as well as trace 

metals and other pollutants from flue-gas cleanup byproducts, into a water body if the 

water body is impaired. The power plant may then be required to seek an alternate water 

source or install additional water treatment equipment. 

The current debate over global climate change and carbon dioxide (CO2) emissions could 

also potentially impact the water resource situation. If power plants are ultimately 

required to implement carbon separation and sequestration technologies to comply with 

future regulations, additional water may be needed for certain process steps and 

groundwater could be impacted by CO2 sequestration (in a manner similar to produced 

water from oil and gas recovery applications). On the other hand, water could potentially 

be recovered from the CO2 stream prior to dry pumping for sequestration or reclaimed 

from produced waters due to underground displacement. A detailed analysis would be 

required to delineate the net water withdrawal and consumption associated with CO2

separation and sequestration and is outside the scope of this study. 

Legislative Activities

The Energy Policy Act of 2005 (Title IX, Subtitle G − Science, Section 979) directs the 

DOE to address energy-water nexus issues and assess the effectiveness of existing 

Federal programs to address energy-water related issues. The direction is for a program 

of research, development, demonstration, and commercial application to: 1) address 

energy-related issues associated with provision of adequate management, and efficient 

use of water; 2) address water-related issues associated with the provision of adequate 

supplies, optimal management, and efficient use of energy; and 3) assess the 

effectiveness of existing programs within the Department and other Federal agencies to 

address these energy and water related issues. 

An amendment to the Energy Policy Act, the Energy-Water Efficiency and Supply 

Technology Bill, was originally introduced in 2004 and has gone through two revisions. 

The current version of the bill would allocate $5 million for the first year and “such sums 

as are necessary for each fiscal year thereafter.” The bill would instruct the Secretary of 

Energy to “establish a national program for the research, development, demonstration, 

and commercial application of economically viable and cost-effective water supply 

technologies.” 

Freshwater Needs for Thermoelectric Generation, August 2006 

A-4 
Drought Conditions

A Government Accountability Office (GAO) report16 prepared in 2003 addressed the 

issue of freshwater supply at the state level. The report indicated that under normal 

rainfall conditions, state water managers in 36 states anticipated shortages in localities, 

regions, or even statewide in the next 10 years (2003 – 2013). The report goes on to say 

that “drought conditions will exacerbate shortage impacts.” 

During the summer of 2005, a joint effort between the Department of the Interior (DOI) 

and the Department of Agriculture (USDA) created Interagency Drought Action Teams 

to coordinate relief efforts in communities in western states facing droughts. A DOI 

report17 about the action teams quotes Secretary (of the Interior) Norton, “Much of the 

Pacific Northwest has been hard hit by drought this year.” 

Power Generation Facility Siting

Power generation facilities will have increasing difficulties siting new plants due to water 

concerns. Concurrently, existing plants will be under increasing pressure to reduce their 

water withdrawal and consumption. In 2006, RDS contacted state government water 

monitoring agencies inquiring if there is a limit to freshwater withdrawal and/or 

consumption by thermoelectric plants in their state. Of the 33 states that responded, 24% 

indicated that plants must either have a senior water right, or purchase such a water right 

from an entity willing to sell it. Another 18% indicated that limitations are imposed 

when water levels fall below the protect flow level and/or in times of water shortage. An 

additional 18% of states responded that water withdrawal and consumption varies 

regionally across the state, with some areas having no limit but other areas that are water 

sparse or over-allocated requiring water rights or special permits. The number of states 

with over-allocated water resources is expected to increase over time. 

Concern about water supply, expressed by state regulators, local decision-makers, and the 

general public, is already impacting power projects across the United States. For 

example, in March 2006, an Idaho state House committee unanimously approved a twoyear moratorium on construction of coal-fired power plants in the state based on 

environmental and water supply concerns.18 Arizona recently rejected permitting for a 

proposed power plant because of concerns about how much water it would withdraw 

from a local aquifer.19 In early 2005, Governor Mike Rounds of South Dakota called for 

a summit to discuss drought-induced low flows on the Missouri River and the impacts on 

irrigation, drinking-water systems, and power plants.20 A coal-fired power plant to be 

built in Wisconsin on Lake Michigan has been under attack from environmental groups 

because of potential effects of the facility’s cooling-water-intake structures on aquatic 

life.21 In February 2006, Diné Power Authority reached an agreement with the Navajo 

Nation to pay $1,000 per acre foot and a guaranteed minimum total of $3 million for 

water for its proposed Desert Rock Energy Project.22 In an article discussing a 1,200 

MW proposed plant in Nevada, opposition to the plant stated, “There’s no way Washoe 

County has the luxury anymore to have a fossil-fuel plant site in the county with the 

water issues we now have. It’s too important for the county’s economic health to allow 

water to be blown up in the air in a cooling tower.”23

Freshwater Needs for Thermoelectric Generation, August 2006 

A-5 
Appendix B 

Water Needs Analysis Methodology 

The purpose of this analysis is to update a 2004 National Energy Technology Laboratory 

(NETL) study to estimate freshwater needs to meet future year thermoelectric generation 

capacity requirements. This analysis uses a more detailed analytical approach and 

incorporates data and projections from the Energy Information Administration’s Annual 

Energy Outlook 2006. Table B-1 summarizes the specific items that are updated in the 

2006 Water Needs Analysis. The additional level of detail and resolution included in the 

2006 analysis required a modified methodology from that used in the 2004 analysis. 

Table B-1 - U.S. Power Generation Industry Water Withdrawal and Use Analysis – Comparison of 

Assumptions and Methodologies 

Item 2004 Analysis 2006 Analysis 

Capacity/Generation 

Projections AEO 2004 AEO 2006 

Geographical Breakdown National National and NERC region 

Cooling Water Source 

Breakdown Freshwater and Saline Freshwater and Saline 

Cooling Water System Type Once-through and wet 

recirculating 

Once-through and recirculating 

(dry, wet, and cooling pond) 

Generation Type Breakdown Total thermoelectric and coal 

Total thermoelectric and coal, 

nuclear, non-coal steam, and natural 

gas combined cycle 

Final Year of Projection 2025 2030 

Cases Six cases representing upper 

and lower bounds 

Five cases with conservative 

assumptions 

Water Use Scaling Factors – 

Geographic Coverage National NERC region with adjustment for capacity factor increase 

Water Use Scaling Factors – 

Coal Plant Design Not included 

Boiler type – subcritical or 

supercritical 

FGD type – wet, dry, or none 

Figure B-1 provides a flowchart depiction of the methodology used to conduct the 

analysis. The five-step approach represents a refined and more robust methodology than 

that used in the 2004 Water Needs Analysis. Each step in the process is described below. 

Freshwater Needs for Thermoelectric Generation, August 2006 

B-1 
Figure B-1 - Methodology for the 2006 Water Needs Analysis 

Develop 

model plants 

to represent 

existing 

thermoelectric fleet

Calculate 

water 

withdrawal 

and 

consumption 

factors

Quality 

control and 

model 

validation

Develop 

future 

cases to 

evaluate

Calculate 

regional 

withdrawal 

and 

consumption 

to 2030

Step 1 Step 2 Step 3 Step 4 Step 5

Step 1: Develop model plants 

To obtain the resolution desired for this analysis, water withdrawal and consumption 

factors were determined for a large number of plant configurations, based on location, 

generation type, cooling water source, cooling system type, and where applicable, boiler 

type and type of flue gas desulfurization (FGD) system. The existing thermoelectric fleet 

was segregated into numerous configurations, called “model plants” using data contained 

in several sources: the NETL Coal Plant Database, EIA-767, and EIA-860. Water 

withdrawal and consumption factors were calculated for each model plant using the 

available data and then used in conjunction with projections from AEO 2006 to provide 

an estimate of future water withdrawal and consumption for various cases. 

The model plant derivation process is detailed below. 

NERC Regions 

Cooling water needs will vary by region due to climatic variations and availability of 

cooling water. Performing the water needs analysis on a regional level, therefore, 

provides a more accurate estimate of cooling water trends than a higher-level analysis. 

To accomplish this, the 13 NERC regions (excluding Alaska and Hawaii) were integrated 

into the NETL Coal Plant Database from the EIA-860 database. 

Thermoelectric Generation Type 

Water withdrawal and consumption factors were determined for thermoelectric power 

plants: coal, nuclear, oil, natural gas and the steam portion of gas-fired combined cycles. 

However, more detailed effort was expended in determining water factors for coal-fired 

power plants. The analysis doe not include non-thermoelectric plants such as combustion 

turbines, renewable generations, etc. 

 

Individual water use estimates were developed for the following thermoelectric 

generation types: 

i. Coal 

ii. Nuclear 

iii. Non-Coal Fossil 

iv. Combined Cycle 

Freshwater Needs for Thermoelectric Generation, August 2006 

B-2 
Model plants for coal in each NERC region were developed using the following 

hierarchy: 

Cooling Water Type (Freshwater/Saline) 

↓

Cooling Water System Type (Once-Through, Wet Recirculating, Dry Recirculating, 

Cooling Ponds) 

↓

Boiler Type (Subcritical, Supercritical) 

↓

FGD Type (Wet, Dry, None) 

Using this hierarchy, a total of 30 model plants are possible for coal in each regione: 

1. Freshwater, once-through, subcritical, wet FGD 

2. Freshwater, once-through, subcritical, dry FGD 

3. Freshwater, once-through, subcritical, no FGD 

4. Freshwater, once-through, supercritical, wet FGD 

5. Freshwater, once-through, supercritical, dry FGD 

6. Freshwater, once-through, supercritical, no FGD 

7. Freshwater, recirculating, subcritical, wet FGD 

8. Freshwater, recirculating, subcritical, dry FGD 

9. Freshwater, recirculating, subcritical, no FGD 

10. Freshwater, recirculating, supercritical, wet FGD 

11. Freshwater, recirculating, supercritical, dry FGD 

12. Freshwater, recirculating, supercritical, no FGD 

13. Freshwater, cooling pond, subcritical, wet FGD 

14. Freshwater, cooling pond, subcritical, dry FGD 

15. Freshwater, cooling pond, subcritical, no FGD 

16. Freshwater, cooling pond, supercritical, wet FGD 

17. Freshwater, cooling pond, supercritical, dry FGD 

18. Freshwater, cooling pond, supercritical, no FGD 

19. Saline, once-through, subcritical, wet FGD 

20. Saline, once-through, subcritical, dry FGD 

 

e

 According to the hierarchy presented, 36 model plant combinations are possible. Six of these 

combinations would be configured with saline cooling ponds. Such a cooling water source is technically 

impractical and, therefore, not included in this analysis. 

Freshwater Needs for Thermoelectric Generation, August 2006 

B-3 
21. Saline, once-through, subcritical, no FGD 

22. Saline, once-through, supercritical, wet FGD 

23. Saline, once-through, supercritical, dry FGD 

24. Saline, once-through, supercritical, no FGD 

25. Saline, recirculating, subcritical, wet FGD 

26. Saline, recirculating, subcritical, dry FGD 

27. Saline, recirculating, subcritical, no FGD 

28. Saline, recirculating, supercritical, wet FGD 

29. Saline, recirculating, supercritical, dry FGD 

30. Saline, recirculating, supercritical, no FGD 

Similar model plants were developed for nuclear, non-coal fossil, and combined cycle, 

but only broken down by cooling water type (freshwater vs. saline) and cooling water 

system type (once-through, recirculating, cooling pond). 

Step 2: Calculate water withdrawal and consumption factors 

For each model plant defined in Step 1, water withdrawal and consumption factors were 

calculated using the data sources outlined above. 

Coal

For coal, the water withdrawal and consumption factors were based on the sum of three 

components: 1) boiler make-up water; 2) FGD make-up water; and 3) cooling water. 

The boiler make-up water component at a coal plant depends on the type of boiler – 

either subcritical or supercritical. The boiler make-up water factors were calculated using 

water balance data contained in Parsons’ “Power Plant Water Consumption Study” 

conducted for NETL in August 2005. Separate values were determined for subcritical 

and supercritical plant configurations, but the values were fixed for all regions, water 

source, cooling type, and FGD type. 

The FGD make-up water component depends on the type of FGD system – either wet or 

dry. Dry FGD systems require much less water than wet FGD systems, for example, so 

different factors must be used. The FGD make-up water factors were calculated using 

material balance data contained in Carnegie Mellon University’s Integrated 

Environmental Control Model (IECM). Separate values were determined for subcritical 

and supercritical plant configurations, but the values were fixed for all regions, water 

source, and cooling type. 

The cooling water component for each model plant was calculated by compiling data 

from the NETL Coal Power Plant Database and EIA-860 for water withdrawal, water 

consumption, and summer capacity. Average water withdrawal (gal/hr), average water 

consumption (gal/hr), and summer capacity were used to calculate average withdrawal 

and consumption scaling factors (gal/kWh) for each model plant in each of the NERC 

regions. The power plant capacity data contained in the NETL database consists of 

Freshwater Needs for Thermoelectric Generation, August 2006 

B-4 
nameplate MW capacity taken from the EIA-767 report. However, the AEO projections 

are based on summer capacity. Therefore, summer capacity (MW) data was obtained 

from the EIA-860 report to calculate the scaling factors. The following methodology was 

used to calculate the average cooling water withdrawal and consumption factors for each 

type of cooling water system: 

o Once-through systems: To maximize plant efficiency during partial load 

operation, power plant operators normally maintain cooling water flow through 

the condenser at full load design rates. Therefore, the cooling water withdrawal 

rate for a once-through cooling water system is dependent on plant capacity (kW) 

and independent of plant electrical generation (kWh). For this reason, the water 

usage factors for once-through systems were determined by dividing the sum of 

the average withdrawal or consumption rate by the sum of the generator summer 

capacity. 

Withdrawal Factor (gal/kWh) = ΣAverage Withdrawal (gal/h) / ΣCapacity (kW) (1a) 

Consumption Factor (gal/kWh) = ΣAverage Consumption (gal/h) / ΣCapacity (kW) (1b) 

 

o Wet Recirculating Systems: Similar to once-through systems, to maximize plant 

efficiency during partial load operation, power plant operators normally maintain 

cooling water flow through the condenser and across the cooling tower at full load 

design rates. However, as more power is produced, the heat load to the cooling 

tower increases, resulting in greater evaporative losses and blowdown and 

consequently, higher water withdrawal requirements. Therefore, water 

withdrawal and consumption are independent of plant capacity (kW) and 

dependent on plant electrical generation (kWh) in wet recirculating systems. For 

this reason, the water usage factors for wet recirculating cooling systems were 

adjusted for each year of the analysis by applying a capacity factor ratio, F, to 

account for the growth in generation. 

Withdrawal Factor (gal/kWh) = F x ΣAverage Withdrawal (gal/h) / ΣCapacity (kW) (2a) 

Consumption Factor (gal/kWh) = F x ΣAverage Consumption (gal/h) / ΣCapacity (kW) (2b) 

Where: 

F = Ratio of capacity factor in year X to capacity factor in baseline year 2003 

o Cooling Ponds: EIA-767 considers cooling ponds to be a type of wet 

recirculating cooling system since heat loss occurs through evaporative loss. 

However, cooling water flow rates for a cooling pond are more similar to oncethrough than wet recirculating systems. Therefore, for this study, water usage 

factors were calculated using the same formula as for once-through systems.

Freshwater Needs for Thermoelectric Generation, August 2006 

B-5 
o Dry Recirculating Systems: For dry recirculating systems, the cooling water 

withdrawal and consumption factors are both assumed to be zero.

Non-Coal Plants

Nuclear, oil steam, gas steam, and natural gas combined-cycle plants were classified 

according to NERC region, cooling water source (fresh or saline), and cooling water 

system (recirculating or once-through). Water usage factors for each plant classification 

were determined using equations 1a, 1b, 2a, and 2b, depending on type of cooling water 

system. 

In calculating water withdrawal and consumption quantities for combined-cycle plants, 

an adjustment was made to account for the fact that the gas turbine portion of the plant 

does not require cooling water. The design capacity of the gas turbine portion of a 

combined-cycle facility is typically twice that of the steam turbine portion; in other 

words, two-thirds of a combined-cycle plant’s total output is derived from the gas 

turbine(s). Therefore, only about one-third of the plant output is used for steam 

generation, with its associated water requirements. For this analysis, water withdrawal 

and consumption factors were applied to only one-third of the combined-cycle capacity. 

Step 3: Quality Control and Model Validation 

Step 3 represents just one of several efforts designed to ensure quality control for the 

analysis. Because models, by definition, are simplified representations of reality, 

absolute model accuracy is impossible to guarantee in any situation. It is important, 

however, to have procedures in place to ensure that output from a given analysis is 

consistent with reality and reasonable expectations. Several steps were taken for the 

water needs analysis to achieve this objective. 

The water withdrawal and consumption factors that were used in the model were 

obtained through a rigorous evaluation of data collected by the Energy Information 

Administration, primarily forms EIA-767 and EIA-860. Data presented on these forms is 

assumed to accurately represent conditions at a particular power plant. A variety of 

reasons, however, could account for errors and discrepancies in the data: lack of 

understanding of the form’s directions, data entered in the wrong places, inaccurate data 

entry, improperly aggregated data, and others. 

The calculated water withdrawal and consumption factors for a given categorical 

breakdown (e.g., NERC region) should fall within a limited range based on generation 

type and cooling type. If the dataset in that categorical breakdown was too small, data 

outliers could have disproportionately impacted the results. While it is impossible to 

eliminate all such errors, the data was carefully vetted to ensure quality data points were 

used. Certain entries were modified or discarded based on accompanying information 

and engineering judgment. For example, if a power plant was designated as a oncethrough facility, but reported cooling water withdrawal and consumption quantities that 

clearly identify it as a recirculating facility, the plant was re-classified as a recirculating 

facility. 

Freshwater Needs for Thermoelectric Generation, August 2006 

B-6 
To ensure that the estimates generated by the water needs analysis model were 

reasonable, power generation data from 1995 was obtained and inserted into the model. 

The calculated water withdrawal and consumption values for thermoelectric generation 

were then compared with U.S. Geologic Service estimates for water withdrawal and 

consumption for 1995. 

Step 4: Develop Future Cases 

Table B-2 summarizes the cases evaluated in the original 2004 analysis and the 2006 

analysis. The effects of emerging issues, particularly the impact of the Clean Water Act 

316(b) regulations,f were incorporated into the selection of the 2006 cases. Comments 

are provided with each of the cases to assess their likelihood and justify the chosen cases. 

Five cases were included in the 2006 Water Needs Analysis, one reflecting status quo 

conditions, two reflecting varying levels of regulations regarding cooling water source, 

one incorporating dry cooling, and one reflecting regulatory pressures to convert existing 

once-through capacity to recirculating capacity. 

To determine total water withdrawal and consumption requirements for thermoelectric 

generation in future years, new capacity additions and existing capacity retirements were 

factored into the analysis. As noted in the table, retirements were modeled based on 

current source withdrawals; in other words, freshwater and saline units were retired from 

service in proportion to their current contributions to total installed capacity, which is 

thought to more accurately reflect industry behavior. Units recently retired and/or placed 

in cold reserve have been removed from service due to age and operational cost 

constraints; cooling water source has played a minimal or nonexistent role. Future 

capacity retirement decisions, therefore, will likely remain more dependent on age and 

operational costs than cooling water source, and should reflect current proportions of 

freshwater and saline water facilities. 

Retired capacity in a given NERC region was broken down by generation type, water 

source, cooling type, and, where applicable, boiler and FGD type, based on the current 

proportion of capacity for each specific combination. The corresponding water 

withdrawal and consumption factors were then applied to the retired capacity to 

determine how much water must be deducted from the withdrawal and consumption 

totals. 

In modeling capacity additions, it was necessary to consider the different thermoelectric 

generation types. A variety of model plants were added based on the case assumptions. 

Expected capacity additions in a given region in a given year, as projected by AEO 2006, 

were apportioned into these model plant categories. Each model plant will have an 

 

f

 The Clean Water Act’s 316(b) regulations require the U.S. Environmental Protection Agency to ensure 

that cooling water intake structures at power plants and other manufacturing facilities reflect the best 

technology available for minimizing adverse environmental impact. The practical impact of these 

regulations is that most new power plants will have to incorporate closed-loop, recirculating cooling 

systems, which overwhelmingly rely on freshwater. 

Freshwater Needs for Thermoelectric Generation, August 2006 

B-7 
associated water withdrawal and consumption factor. The corresponding capacity (kW) 

for each model plant category was used with the withdrawal and consumption factors to 

calculate incremental water withdrawal and consumption. 

The model plants for the five cases are listed in Table B-3. Because of the resolution 

provided in this analysis for coal-fired power plants, more model plants were developed 

for coal than for the other generation types. Several notes are in order regarding the coal 

model plants: 

• For pulverized coal plants, new additions are expected to favor supercritical boiler 

technology. Nationwide, the current split between subcritical and supercritical 

boiler technology capacity is 73% subcritical/27% supercritical, reflecting greater 

industry experience and familiarity with subcritical technology. Pressure from 

several sources – environmental entities, state utility commissions, the threat of 

CO2 regulations – is increasing utility interest in supercritical boiler technology. 

A majority of the coal-fired power plants currently under construction or planned 

will rely on supercritical boiler technology. In selecting model coal plants for 

new additions, therefore, a 70% supercritical/30% subcritical split was employed. 

See Appendix B for further information. 

• For coal-fired power plants equipped with flue gas desulfurization equipment, 

water withdrawal and consumption rates can exhibit relatively significant 

differences based on whether the FGD is a wet or dry system. Since all new 

pulverized coal-fired power plants will need FGD systems to comply with 

emission regulations, future capacity additions must be apportioned by FGD type. 

Since emission regulations do not dictate technology selection, the analysis 

apportions FGD type to new capacity additions based on the existing split in the 

coal-fired power fleet (by summer capacity), which is 90% wet/10% dry. 

• The Annual Energy Outlook assumes that a portion of new coal-fired capacity will 

utilize integrated gasification combined-cycle (IGCC) technology. The water 

requirements for IGCC facilities differ from those at pulverized coal facilities. 

While both require cooling water, IGCC requires substantially less since a large 

fraction of the output from an IGCC plant is produced from the combustion 

turbines, which require minimal water. Moreover, since IGCC relies on water for 

significant process (non-cooling) use, it is unlikely that a saline water source 

would be desirable. The model IGCC coal plant, therefore, is restricted to 

freshwater use. 

As discussed above, model plants for the non-coal thermoelectric generation capacity – 

nuclear, oil steam, gas steam, and natural gas combined cycle – were broken down by 

water source (fresh or saline) and cooling water type (once-through or wet recirculating) 

based on data from the EIA-767 and EIA-860 databases. Two model plants account for 

all likely new non-coal thermoelectric additions: a plant using a freshwater recirculating 

system and a plant using a saline once-through system. For Case 4, an additional model 

plant with dry cooling is included for both coal and non-coal generation types. 

Freshwater Needs for Thermoelectric Generation, August 2006 

B-8 
Table B-2 - Case Selection, 2004 vs. 2006 

2004 Water Needs Analysis 

Case description Comments 

Case 1: All additions and retirements 

occur at facilities using freshwater. 

Reasonable. While the vast majority of new additions will use 

freshwater due to 316(b) regulations, it is unlikely that the 

majority of retirements will be from freshwater facilities. 

Retirement decisions will depend more on age and operational 

costs than on cooling water source. 

Case 2: Additions and retirements are 

proportional to current source 

withdrawals (70% freshwater/30% 

saline). 

Reasonable. As discussed for Case 1, retirement decisions will 

depend on age and operational costs, which will likely mirror 

the proportional split between freshwater and saline. For 

additions, however, 316(b) regulations will likely lead to a 

higher proportion of freshwater facilities since saline water is 

incompatible with wet recirculation systems. 

Case 3: All additions and retirements 

occur at facilities using saline water. 

Unlikely. Due to 316(b) regulations, saline water will likely 

account for a significantly smaller percentage of new additions. 

Retirements may slightly favor saline, but decision will depend 

more on age and operational costs. 

Case 4: Additions occur at freshwater 

facilities, while retirements occur at 

saline facilities. 

Reasonable. Although retirements are likely to be more 

proportional to current source withdrawals, as discussed above. 

Case 5: Additions occur at saline 

facilities, while retirements occur at 

freshwater facilities. 

Extremely unlikely. 316(b) regulations will make saline a 

difficult choice for additions. No regulatory or operational 

trends indicate that retirements would favor freshwater. 

Case 6: All retired coal units use oncethrough cooling and are repowered 

using the existing once-through 

system. Additions reduced by the 

repowered units. 

Unlikely. Via repowering, units would be subject to new source 

regulations, which favor recirculating systems and the use of 

freshwater. 

2006 Water Needs Analysis 

Case Description Rationale 

Case 1: Additions and retirements 

proportional to current water source 

and type of cooling system. 

Status quo scenario case. Assumes additions and retirements 

follow current trends. 

Case 2: All additions use freshwater 

and wet recirculating cooling, while 

retirements are proportional to current 

water source and cooling system. 

Regulatory-driven case. Assumes 316(b) and future regulations 

dictate the use of recirculating systems for all new capacity. 

Retirement decisions hinge on age and operational costs rather 

than water source and type of cooling system. 

Case 3: 90% of additions use 

freshwater and wet recirculating 

cooling, and 10% of additions use 

saline water and once-through cooling, 

while retirements are proportional to 

current water source and cooling 

system. 

Regulatory-light case. New additions favor the use of freshwater 

recirculating systems, but some saline capacity is permitted. 

Retirement decisions remain tied to age and operational costs, 

tracking current source withdrawals. 

Case 4: 25% of additions use dry 

cooling and 75% of additions use 

freshwater and wet recirculating 

cooling. Retirements are proportional 

to current water source and cooling 

system. 

Dry cooling case. Regulatory and public pressures result in 

significant market penetration of dry cooling technology. 

Retirement decisions remain tied to age and operational costs, 

tracking current source withdrawals. 

Case 5: Additions use freshwater and 

wet recirculating cooling, while 

Conversion case. Same as Case 2, except regulatory and public 

pressures compel state agencies to dictate the conversion of a 

Freshwater Needs for Thermoelectric Generation, August 2006 

B-9 
retirements are proportional to current 

water source and cooling system. 5% 

of existing freshwater once-through 

cooling capacity retrofitted with wet 

recirculating cooling every 5 years 

starting in 2010. 

significant amount of existing freshwater once-through cooling 

systems to wet recirculating. 

Table B-3 - Model Plants for New Capacity Additions

Case 1 

Coal • Pulverized coal, freshwater, recirculating cooling system 

o 75% supercritical/25% subcritical 

o Wet FGD/dry FGD based on existing split 

• Pulverized coal, saline water, once-through cooling system 

o 75% supercritical/25% subcritical 

o Wet FGD/dry FGD based on existing split 

• Integrated gasification combined-cycle, freshwater, recirculating 

Nuclear • Freshwater, recirculating cooling system 

• Saline water, once-through cooling system 

Non-coal fossil • Freshwater, recirculating cooling system 

• Saline water, once-through cooling system 

Case 2 

Coal • Pulverized coal, freshwater, recirculating cooling system 

o 75% supercritical/25% subcritical 

o Wet FGD/dry FGD based on existing split 

• Integrated gasification combined-cycle, freshwater, recirculating 

Nuclear • Freshwater, recirculating cooling system 

Non-coal fossil • Freshwater, recirculating cooling system 

Case 3 

Coal • Pulverized coal, freshwater, recirculating cooling system 

o 75% supercritical/25% subcritical 

o Wet FGD/dry FGD based on existing split 

• Pulverized coal, saline water, once-through cooling system 

o 75% supercritical/25% subcritical 

o Wet FGD/dry FGD based on existing split 

• Integrated gasification combined-cycle, freshwater, recirculating 

Nuclear • Freshwater, recirculating cooling system 

• Saline water, once-through cooling system 

Non-coal fossil • Freshwater, recirculating cooling system 

• Saline water, once-through cooling system 

Case 4 

Coal • Pulverized coal, freshwater, recirculating cooling system 

o 75% supercritical/25% subcritical 

o Wet FGD/dry FGD based on existing split 

• Pulverized coal, freshwater, dry cooling system 

o 75% supercritical/25% subcritical 

o Wet FGD/dry FGD based on existing split 

• Integrated gasification combined-cycle, freshwater, recirculating 

• Integrated gasification combined-cycle, dry cooling system 

Nuclear • Freshwater, recirculating cooling system 

• Dry cooling system 

Freshwater Needs for Thermoelectric Generation, August 2006 

B-10 
Non-coal fossil • Freshwater, recirculating cooling system 

• Dry cooling system 

Case 5 

Coal • Pulverized coal, freshwater, recirculating cooling system 

o 75% supercritical/25% subcritical 

o Wet FGD/dry FGD based on existing split 

• Integrated gasification combined-cycle, freshwater, recirculating 

Nuclear • Freshwater, recirculating cooling system 

Non-coal fossil • Freshwater, recirculating cooling system 

Step 5: Calculate regional withdrawal and consumption to 2030 

Step 5 integrates the water withdrawal and consumption factors calculated in Step 2 with 

the various cases defined in Step 4 to assess the regional and national impacts on water 

withdrawal and consumption out to 2030. 

The Annual Energy Outlook provides projections of future electricity generating capacity 

by year, by generation type and by NERC region. Apportioning this capacity among the 

chosen model plants for a given case and then applying the water withdrawal and 

consumption factors enables one to estimate water withdrawal and consumption trends. 

For a given case in a given region, the capacity additions and retirements projected by 

AEO 2006 were first divided between freshwater and saline water based on the source 

withdrawal split for each technology type (coal, nuclear, non-coal fossil), as determined 

using existing fleet data. The additions and retirements were further apportioned among 

cooling water system type (once-through, recirculating), again using existing fleet splits. 

For nuclear and non-coal fossil, the water withdrawal and consumption factors 

determined in Step 2 were then applied to the resulting capacity amounts to calculate 

water withdrawal and consumption totals. 

For coal, further segregation was necessary before performing the calculations. The 

additions and retirements were further apportioned by technology type (supercritical and 

subcritical boilers). Retirements were divided based on the existing fleet split between 

supercritical and subcritical technology. Additions were divided between supercritical 

and subcritical boilers at a 70/30 ratio to reflect a growing preference for supercritical 

technology, as described above in Step 4 and in Appendix C. The additions also must 

accommodate new IGCC plants; AEO projections for IGCC were used to apportion 

capacity amounts by region. Finally, coal retirements and additions were apportioned by 

FGD type (wet, dry, none) using existing fleet data. The water withdrawal and 

consumption values determined in Step 2 were applied to the segregated capacity 

quantities determined in Step 5 to calculate water withdrawal and consumption totals. 

The calculations were a result of summing the results for each model plant in each region. 

The following is an example formula to calculate water withdrawal that was used for a 

model plant: 

Freshwater Needs for Thermoelectric Generation, August 2006 

B-11 
Water Withdrawal (gal/hr) = A x B x C (3) 

Where: 

A = Total regional capacity, kW 

B = Proportion of capacity assigned to model plant, %/100 

C = Capacity factor-weighted water use scaling factor for model plant, gal/kWh 

 

Freshwater Needs for Thermoelectric Generation, August 2006 

B-12 
Appendix C 

Future Coal-Fired Power Plant Boiler Type 

Supercritical versus Subcritical

The water analysis uses different water use scaling factors for coal-fired power plants 

based on boiler type. A supercritical boiler – operating at steam conditions above the 

critical point – is more efficient and therefore requires less cooling water flow than a 

subcritical boiler for an equivalent amount of electrical generation output. The critical 

point represents the highest temperature and pressure at which a substance can exist as a 

vapor and liquid in equilibrium. The critical point for water is 3200 psia and 705°F. 

Today’s supercritical boilers operate at steam conditions of approximately 3500 psia and 

1000°F compared to subcritical boilers that operate at approximately 2400 psia or less 

and 1000°F. 

Table C-1 presents a summary of the breakdown by boiler type for currently operating 

U.S. coal-fired power plants according to data taken from Platt’s UDI Power Plant 

Database. The current boiler type breakdown by MW capacity is 27% supercritical and 

73% subcritical. It should also be noted that supercritical boilers tend to be significantly 

larger in capacity. The average size of supercritical boilers is 743 MW compared to 234 

MW for subcritical boilers. 

Table C-1 – Boiler Type for Existing Plants 

Operating Plants Total 

Supercritical Subcritical 

No. Units 1,136 117 1,019 

Total Capacity, MW 325,651 86,903 238,748 

Average Unit Capacity, MW 287 743 234 

% Total Capacity Base 27% 73% 

Table C-2 presents a similar summary by boiler type for coal-fired power plants either 

under construction or planned also taken from Platt’s UDI Power Plant Database. 

However, not all of the plants reported boiler type. For those plants that boiler type is 

reported, the breakdown by capacity is 55% supercritical and 45% subcritical. Similar to 

the currently operating plants, the average size of supercritical plants is 719 MW 

compared to 312 MW for subcritical plants. Since it appears that plant capacity 

correlates fairly well with boiler type, the unreported plants are segregated into two plant 

sizes – greater than or equal to 500 MW (87%) and less than 500 MW (13%). 

Freshwater Needs for Thermoelectric Generation, August 2006 

C-1 
Table C-2 – Boiler Type for Future Plants – As Reported 

Plants Under Boiler Type Reported Boiler Type Not Reported 

Construction or 

Planned 

Total 

Total 

Supercritical Subcritical Total ≥ 500 

MW 

< 500 

MW 

No. Units 86 49 17 32 37 26 11 

Total Capacity, 

MW 42,835 22,203 12,225 9,978 20,632 17,887 2,745 

Average 

Capacity, MW 498 453 719 312 558 688 250 

% Total 

Capacity 55% 45% 87% 13% 

Based on the boiler type data in Table C-1 and reported boiler type data in Table C-2, it is 

apparent that plant capacity correlates fairly well with boiler type. As a result, the 

unreported plants in Table C-2 that were segregated by plant capacity can also be 

categorized by boiler type. Plants with a capacity greater than or equal to 500 MW are 

assumed to be supercritical and those with a capacity less than 500 MW are assumed to 

be subcritical. Table C-3 presents the result of this categorization by combining the 

reported and unreported plant data from Table C-2. Therefore, future coal-fired plant 

capacity is assumed to be split as 70% supercritical and 30% subcritical for the water 

analysis. 

Table C-3 – Boiler Type for Future Plants - Combined 

Plants Under Construction or 

Planned Total 

Supercritical Subcritical 

No. Units 86 43 43 

Total Capacity, MW 42,835 30,112 12,723 

Average Capacity, MW 498 700 296 

% Total Capacity 70% 30% 

Freshwater Needs for Thermoelectric Generation, August 2006 

C-2 
Appendix D 

Water Withdrawal and Consumption Factors 

Table D-1 – National Average Withdrawal and Consumption Factors for Model Coal Plants 

Model Plant Withdrawal 

Factor (gal/kWh) 

Consumption 

Factor (gal/kWh) 

Freshwater, Once-Through, Subcritical, Wet FGD 27.113 0.138 

Freshwater, Once-Through, Subcritical, Dry FGD 27.088 0.113 

Freshwater, Once-Through, Subcritical, No FGD 27.046 0.071 

Freshwater, Once-Through, Supercritical, Wet FGD 22.611 0.124 

Freshwater, Once-Through, Supercritical, Dry FGD 22.590 0.103 

Freshwater, Once-Through, Supercritical, No FGD 22.551 0.064 

Freshwater, Recirculating, Subcritical, Wet FGD 0.531 0.462 

Freshwater, Recirculating, Subcritical, Dry FGD 0.506 0.437 

Freshwater, Recirculating, Subcritical, No FGD 0.463 0.394 

Freshwater, Recirculating, Supercritical, Wet FGD 0.669 0.518 

Freshwater, Recirculating, Supercritical, Dry FGD 0.648 0.496 

Freshwater, Recirculating, Supercritical, No FGD 0.609 0.458 

Freshwater, Cooling Pond, Subcritical, Wet FGD 17.927 0.804 

Freshwater, Cooling Pond, Subcritical, Dry FGD 17.902 0.779 

Freshwater, Cooling Pond, Subcritical, No FGD 17.859 0.737 

Freshwater, Cooling Pond, Supercritical, Wet FGD 15.057 0.064 

Freshwater, Cooling Pond, Supercritical, Dry FGD 15.035 0.042 

Freshwater, Cooling Pond, Supercritical, No FGD 14.996 0.004 

Table D-2 – National Average Withdrawal and Consumption Factors for Model Nuclear Plants 

Model Plant Withdrawal Factor 

(gal/kWh) 

Consumption Factor 

(gal/kWh) 

Freshwater, Once-Through 31.497 0.137 

Freshwater, Recirculating 1.101 0.624 

Table D-3 – National Average Withdrawal and Consumption Factors for Model Fossil Non-Coal 

Plants 

Model Plant Withdrawal Factor 

(gal/kWh) 

Consumption Factor 

(gal/kWh) 

Freshwater, Once-Through 22.74 0.09 

Freshwater, Recirculating 0.25 0.16 

Freshwater, Cooling Pond 7.89 0.11 

Table D-4 – National Average Withdrawal and Consumption Factors for Model IGCC/NGCC Plants 

Model Plant Withdrawal 

Factor (gal/kWh) 

Consumption 

Factor (gal/kWh) 

NGCC, Freshwater, Once-Through 9.01 0.02 

NGCC, Freshwater, Recirculating 0.15 0.13 

NGCC, Freshwater, Cooling Pond 5.95 0.24 

NGCC Air Cooled 0.004 0.004 

IGCC, Freshwater, Recirculating 0.226 0.173 

Freshwater Needs for Thermoelectric Generation, August 2006 

D-1 
Appendix E 

Combined-Cycle Power Plants: 

Relative Contributions from Gas and Steam Turbines

Combined-cycle power plants integrate the power generating capabilities of gas turbines 

and steam turbines in a highly efficient manner. The waste heat generated by fuel 

combustion in the gas turbine is recovered in a heat recovery steam generator, producing 

steam that is then used to generate additional power in the steam turbine. A common rule 

of thumb for combined-cycle design is that the gas turbine capacity is about twice that of 

the steam turbine (i.e., steam turbine output represents about one-third of total plant 

output). 

The water needs analysis incorporates this rule of thumb by applying the water 

withdrawal and consumption factors to only one-third of the combined-cycle capacity. 

To justify this assumption, the Platts World Electric Power Plants Database was 

analyzed. For those plants reporting gas turbine and steam turbine capacity in a 

combined-cycle configuration, the database produced the numbers shown in the table 

below. 

Table E-1 - Gas and Steam Turbine Contribution 

Capacity (MW) Percentage Number of units Percentage 

Gas turbines in 

combined-cycle 

configuration 

93,526 62.1% 846 63.2% 

Steam turbines in 

combined-cycle 

configuration 

57,068 37.9% 493 36.8% 

Total 150,594 100.0% 1339 100.0% 

Steam turbine capacity represents about 38% of total combined-cycle capacity. While the 

data do not precisely equal the 2:1 ratio posited by the rule of thumb, the agreement is 

fairly close. Industry product evolution and individual plant design data also support the 

2:1 ratio. Siemens Power Generation recently expanded its product portfolio with the 

SGT5-8000H gas turbine, featuring advanced H-class efficiency.24 This turbine will be 

capable of producing about 340 MW in simple-cycle configuration, and about 530 MW 

in combined-cycle configuration, resulting in a steam turbine percentage of 35.8%. In the 

forthcoming NETL report, “2006 Cost and Performance Comparison of Fossil Energy 

Power Plants,” the steam turbine in the natural gas-fired combined-cycle design 

represents 29.2% of total plant output.25

Based on this information, assuming that the water scaling factors should only be applied 

to one-third of the generating capacity for combined-cycle plants appears quite 

reasonable. 

Freshwater Needs for Thermoelectric Generation, August 2006 

E-1 
Appendix F 

Results from Statistical Analysis of Water Usage Factor Data 

Figure F-1 – Boxplot for All Water Usage Factor Data for 

Coal Recirculating Subcritical Category 

Recirculating Subcritical

120000.00

100000.00

80000.00

60000.00

40000.00

20000.00

0.00

gal/MWh

Figure F-2 - Boxplot for Water Usage Factor Data for Coal Recirculating 

Subcritical Category with Outliers Eliminated 

Recirculating Subcritical

800.00

600.00

400.00

200.00

0.00

gal/MWh

Freshwater Needs for Thermoelectric Generation, August 2006 

F-1 
Figure F-3 – Boxplot for All Water Usage Factor Data for 

Coal Recirculating Supercritical Category 

Recirculating Supercritical

100000.00

80000.00

60000.00

40000.00

20000.00

0.00

gal/MWh

Figure F-4 - Boxplot for Water Usage Factor Data for Coal Recirculating 

Supercritical Category with Outliers Eliminated 

Recirculating Supercritical

1200.00

1000.00

800.00

600.00

400.00

200.00

gal/MWh

Freshwater Needs for Thermoelectric Generation, August 2006 

F-2 
Figure F-5 – Boxplot for All Water Usage Factor Data for 

Coal Once-Through Subcritical Category 

Once-Through Subcritical

10000000.00

8000000.00

6000000.00

4000000.00

2000000.00

0.00

gal/MWh x Design Temperature Rise

Figure F-6 - Boxplot for Water Usage Factor Data for Coal Once-Through 

Subcritical Category with Outliers Eliminated 

Once-Through Subcritical

1000000.00

800000.00

600000.00

400000.00

200000.00

gal/MWh x Design Temperature Rise

Freshwater Needs for Thermoelectric Generation, August 2006 

F-3 
Figure F-7 – Boxplot for All Water Usage Factor Data for 

Coal Once-Through Supercritical Category 

Once-Through Supercritical

1000000.00

800000.00

600000.00

400000.00

200000.00

gal/MWh x Design Temperature Rise

Figure F-8 - Boxplot for Water Usage Factor Data for Coal Once-Through 

Supercritical Category with Outliers Eliminated 

Once-Through Supercritical

600000.00

550000.00

500000.00

450000.00

400000.00

350000.00

300000.00

250000.00

gal/MWh x Design Temperature Rise

Freshwater Needs for Thermoelectric Generation, August 2006 

F-4 
Figure F-9 – Boxplot for All Water Usage Factor Data for 

Coal Cooling Pond Subcritical Category 

Cooling Pond Subcritical

800000.00

600000.00

400000.00

200000.00

0.00

gal/MWh x Design Temperature Rise

Figure F-10 – Boxplot for All Water Usage Factor Data for 

Coal Cooling Pond Supercritical Category 

Cooling Pond Supercritical

1750000.00

1500000.00

1250000.00

1000000.00

750000.00

500000.00

gal/MWh x Design Temperature Rise

Freshwater Needs for Thermoelectric Generation, August 2006 

F-5 
Figure F-11 - Boxplot for Water Usage Factor Data for Coal Cooling Pond 

Supercritical Category with Outliers Eliminated 

Cooling Pond Supercritical

502000.00

500000.00

498000.00

496000.00

494000.00

492000.00

490000.00

gal/MWh x Design Temperature Rise

Figure F-12 – Boxplot for All Water Usage Factor Data for 

Fossil Non-Coal Recirculating Category 

Fossil Non-Coal Recirculating

400000.00

200000.00

0.00

gal/MWh

Freshwater Needs for Thermoelectric Generation, August 2006 

F-6 
Figure F-13 - Boxplot for Water Usage Factor Data for Fossil Non-Coal 

Recirculating Category with Outliers Eliminated 

Fossil Non-Coal Recirculating

1200.00

1000.00

800.00

600.00

400.00

200.00

0.00

gal/MWh

Figure F-14 – Boxplot for All Water Usage Factor Data for 

Fossil Non-Coal Once-Through Category 

Fossil Non-Coal Once-Through

10000000.00

8000000.00

6000000.00

4000000.00

2000000.00

0.00

gal/MWh x Design Temperature Rise

Freshwater Needs for Thermoelectric Generation, August 2006 

F-7 
Figure F-15 - Boxplot for Water Usage Factor Data for Fossil Non-Coal 

Once-Through Category with Outliers Eliminated 

Fossil Non-Coal Once-Through

1200000.00

1000000.00

800000.00

600000.00

400000.00

200000.00

0.00

gal/MWh x Design Temperature Rise

Figure F-16 – Boxplot for All Water Usage Factor Data for 

Fossil Non-Coal Cooling Pond Category 

Fossil Non-Coal Cooling Pond

400000.00

200000.00

0.00

gal/MWh x Design Temperature Rise

Freshwater Needs for Thermoelectric Generation, August 2006 

F-8 
Figure F-17 – Boxplot for All Water Usage Factor Data for 

Nuclear Recirculating Category 

Nuclear Recirculating

125000.00

100000.00

75000.00

50000.00

25000.00

0.00

gal/MWh

Figure F-18 - Boxplot for Water Usage Factor Data for Nuclear 

Recirculating Category with Outliers Eliminated 

Nuclear Recirculating

3000.00

2500.00

2000.00

1500.00

1000.00

500.00

0.00

gal/MWh

Freshwater Needs for Thermoelectric Generation, August 2006 

F-9 
Figure F-19 – Boxplot for All Water Usage Factor Data for 

Nuclear Once-Through Category 

Nuclear Once-Through

2500000.00

2000000.00

1500000.00

1000000.00

500000.00

0.00

gal/MWh x Design Temperature Rise

Figure F-20 - Boxplot for Water Usage Factor Data for Nuclear 

Once-Through Category with Outliers Eliminated 

Nuclear Once-Through

1000000.00

800000.00

600000.00

400000.00

200000.00

gal/MWh x Design Temperature Rise

Freshwater Needs for Thermoelectric Generation, August 2006 

F-10 
References 

 

1

 Energy Information Administration, Annual Energy Outlook 2006 with Projections to 2030, 

http://www.eia.doe.gov/oiaf/aeo/index.html, February 2006. 2

 DOE/NETL. Estimating Freshwater Needs to Meet 2025 Electricity Generating Capacity Forecasts. 

http://www.netl.doe.gov/technologies/coalpower/ewr/pubs/Estimating%20Freshwater%20Needs%20to%20

2025.pdf , June 2004. 3 Power Plant Water Consumption Study, Michael G. Klett, Norma J. Kuehn, Ronald L. Schoff, Vladimir 

Vaysman, Jay S. White, U.S. Department of Energy, National Energy Technology Laboratory, August 

2005. 

http://www.netl.doe.gov/technologies/coalpower/gasification/pubs/pdf/WaterReport_IGCC_Final_August2

005.pdf

4

 United States Geological Survey (USGS). Estimated Use of Water in the United States in 2000; USGS 

Circular 1268; March 2004. 

5

 USGS. Estimated Use of Water in the United States in 1995; USGS Circular 1200; 1998. 

http://water.usgs.gov/watuse/pdf1995/pdf/circular1200.pdf

6

 Energy Information Administration. Annual Energy Outlook 2006, EIA Report No. DOE/EIA0383(2006); February 2006. 

7

 GAO, Freshwater Supply: States’ View of How Federal Agencies Could Help Them Meet the Challenges 

of Expected Shortages, July 2003. 8

 U.S. Census Bureau, http://www.census.gov/population/cen2000/map01.gif 9

 National Oceanic and Atmospheric Administration, National Climatic Data Center 

10 USGS and USDOI, Water Availability for the Western United States – Key Scientific Challenges, USGS 

Circular 1261, 2005 

11 Platts, The McGraw-Hill Companies, Inc., North American Energy Business Directory, World Electric 

Power Plants Database. December 2005. 12 EPRI, Water & Sustainability (Volume 3): U.S. Water Consumption for Power Production – The Next 

Half Century, Topical Report No. 1006786, March 2002. 13 Integrated Environmental Control Model, Carnegie Mellon University, 2004. http://www.iecmonline.com/

14 Timothy B. Wheeler, The Baltimore Sun, Running Dry? Maryland’s Growth Could Threaten Water 

Supplies, and Towns Have Been Forced to Curtail Development, February 5, 2006 15 National Energy Technology Laboratory, Power Plant Water Usage and Loss Study, August 2005. 16 GAO, Freshwater Supply: States’ View of How Federal Agencies Could Help Them Meet the Challenges 

of Expected Shortages, July 2003 17 DOI, Federal Drought Action Team will Coordinate Drought Relief Assistance to Western States, July 

2005 

18 Shea Anderson, Reuters, Idaho Committee Adopts Moratorium on Coal Power, March 14, 2006. 19 Land Letter. Western Power Plants Come Under Scrutiny as Demand and Drought Besiege Supplies;

March 4, 2004; http://www.eenews.net/Landletter.htm 20 Billingsgazette.com. South Dakota Governor Seeks Summit on Missouri River, February 2005. 21 Milwaukee Journal Sentinel. Wisconsin Energy Just Can’t Stay Out of the News with Their Intake 

Structures, February 18, 2005. 22 Erny Zah, The Daily Times, Desert Rock Water Agreement Passes Navajo National Committee, February 

2, 2006 

23 The Associated Press, Sempra Energy Halts Gerlach Project Study, March 8, 2006 24 http://www.powergeneration.siemens.com/en/gasturbinesitem/ls/sgt5_8000h/index.cfm 25 U.S. Department of Energy, National Energy Technology Laboratory, 2006 Cost and Performance 

Comparison of Fossil Energy Power Plants, June 2006 26 Devore, Jay L., Probability and Statistics for Engineering and the Sciences, Fifth Edition, Duxbury 

Thomson Learning, Pacific Grove, CA, 2000. 

27 http://www.netmba.com

Freshwater Needs for Thermoelectric Generation, August 2006 

R-1