United States 

Environmental Protection 

Agency

EPA 231-R-98-014

July 1998

Office of Policy Planning & Evaluation

(2126)

Climate Wise 

Wise Rules for

Industrial Efficiency

Wise Rules for

Industrial Efficiency

A T OOL K IT FOR

E STIMATING

E NERGY S AVINGS

AND G REENHOUSE

G A S E MISSIONS

R EDUCTIONS
CLIMATE WISE

Wise Rules for

Industrial Efficiency

A Tool Kit for Estimating Energy Savings and 

Greenhouse Gas Emissions Reductions
For more information on the Climate Wise Program, call the Wise Line at 1-800-459-WISE.

Climate Wise would like to thank the following people for their assistance and input:

■ Michael R. Muller, Director, Office of Industrial Productivity & Energy Assessment, Rutgers University.

■ Steven C. Schultz, Energy Engineering Specialist, 3M Company.

■ Kenneth F. Kraly, Director of Engineering, Cosmair, Inc.

■ Harry A. Kauffman, Director Energy and Fire Policy Management, Johnson & Johnson.

■ Lee Link and Rob Penney, Energy Ideas Clearinghouse, Washington State Energy Office.

■ George M. Wheeler, Director, Industrial Assessment Center, Oregon State University.

This document was developed for the U.S. Environmental Protection Agency under contract number EPA 68-W6-0029.
Table ofContents

1. Introduction..............................................................................................................................................................................................1

The ClimateWise Program ...................................................................................................................................................................1

Overview...............................................................................................................................................................................................1

Information Sources .............................................................................................................................................................................1

Using the Toolkit...................................................................................................................................................................................3

2. Boilers......................................................................................................................................................................................................5

Introduction .........................................................................................................................................................................................5

Boiler Load Management .....................................................................................................................................................................6

Tune-Up and Air/Fuel Ratio Optimization...........................................................................................................................................6

Burner Repalcement .............................................................................................................................................................................7

Stack Heat Losses and Waste Heat Recovery.........................................................................................................................................7

Blowdown Control and Waste Heat Recovery .....................................................................................................................................7

Summary of Wise Rules for Boiler Systems .........................................................................................................................................8

3. Steam Systems......................................................................................................................................................................................10

Introduction .......................................................................................................................................................................................10

Maintenance of Steam Traps...............................................................................................................................................................10

Reducing Leaks...................................................................................................................................................................................11

Reducing Heat Losses .........................................................................................................................................................................11

Vapor Recompression .........................................................................................................................................................................11

Condensate .........................................................................................................................................................................................11

Summary of Wise Rules for Steam Systems .......................................................................................................................................12

4. Process Heating.....................................................................................................................................................................................14

Introduction .......................................................................................................................................................................................14

Insulation and Heat Containment .....................................................................................................................................................14

Combustion Air Control ...................................................................................................................................................................15

Process Waste Heat Recovery .............................................................................................................................................................15

Specific Process Heat Applications .....................................................................................................................................................15

Direct Heating ...................................................................................................................................................................................16

Summary of Wise Rules for Process Heating .....................................................................................................................................16

5. Waste Heat Recovery and Cogeneration..............................................................................................................................................18

Introduction .......................................................................................................................................................................................18

Waste Heat Recovery .........................................................................................................................................................................18

Cogeneration.......................................................................................................................................................................................19

Summary of Wise Rules for Heat Recovery and Cogeneration .........................................................................................................20

Table of Contents Wise Rules Page i
Page ii Wise Rules Table of Contents

6. Compressed Air Systems......................................................................................................................................................................22

Introduction .......................................................................................................................................................................................22

Use Cooler Intake Air.........................................................................................................................................................................23

Match Compressor with Load Requirement.......................................................................................................................................23

Reduce Compressor Air Pressure .......................................................................................................................................................23

Reduce or Eliminate Compressed Air Use .........................................................................................................................................24

Eliminate Air Leaks.............................................................................................................................................................................24

Recover Waste Heat ...........................................................................................................................................................................24

Filters and Coolers .............................................................................................................................................................................25

Summary of Wise Rules for Compressed Air Systems .......................................................................................................................25

7. Process Cooling.....................................................................................................................................................................................27

Introduction .......................................................................................................................................................................................27

Energy Efficient Chillers and Refrigeration Units...............................................................................................................................27

Cooling Tower Water .........................................................................................................................................................................28

Refrigeration and Chillers...................................................................................................................................................................28

Freezing...............................................................................................................................................................................................28

Variable Speed Drives .........................................................................................................................................................................29

Summary of Wise Rules for Process Cooling Systems .......................................................................................................................29

Appendix A: Sector-Specific Energy Savings Potential...........................................................................................................................31

Appendix B: Conversion Factors and Emission Coefficients..................................................................................................................52

Appendix C: Summary of Wise Rules.......................................................................................................................................................55

Appendix D: Key References & Resources ..............................................................................................................................................60
1. Introduction Wise Rules Page 1

1. Introduction

The Climate Wise Program

Climate Wise is a partnership initiative sponsored by the U.S.

EPA, with technical support from the U.S. DOE, designed to

stimulate the voluntary reduction of greenhouse gas emissions

among participating manufacturing companies. Climate Wise

hopes to spur innovation by encouraging broad goals, providing

technical assistance, and allowing organizations to identify the

most cost-effective ways to reduce greenhouse gas emissions.

Climate Wise currently has more than 400 partners, representing

about 12 percent of U.S. industrial energy use. As part of their

Climate Wise commitment, partner companies across the country

develop comprehensive Action Plans that describe their energy

efficiency and pollution prevention goals, the specific actions

undertaken to achieve these goals, the time frame for implementing commitments, and estimates of the impacts on energy, costs,

and emissions from these actions. To date, Climate Wise Partner

companies have submitted Action Plans detailing more than 1,000

individual actions to reduce greenhouse gas emissions and prevent

pollution. About half of these actions pertain to energy efficiency

measures in industrial operations such as: boiler and steam systems, compressed air systems, energy management operations,

motor systems, process heating, and process improvements.

Partner companies also pursue non-process energy efficiency measures such as lighting, HVAC, and building shell improvements,

as well as water conservation, recycling, pollution prevention and

educational outreach. 

Overview

The Wise Rules for Industrial Efficiency – “Wise Rules Tool Kit” –

was developed to help partners make the most of their Climate

Wise participation and generate interest and commitment in 

support of energy efficiency and pollution prevention efforts. It

provides Climate Wise Partners with simple rules for estimating

energy savings and greenhouse gas emissions reductions from a

wide range of industrial energy efficiency measures, based on a

large number of resources. Information on typical cost savings and

paybacks are also provided. The Wise Rules focus on six process

energy end-uses including boilers, steam systems, process heating,

waste heat recovery and cogeneration, compressed air systems, and

process cooling. Six chapters describe energy efficiency measures

and provide Wise Rules on typical energy and cost savings for each

of these major process end-uses. This information can help your

company identify and evaluate alternative energy efficiency activities. It can also help you to develop your Climate Wise Action Plan

— your statement of commitment under your Climate Wise

Participation Agreement.

Climate Wise will update this document periodically as we gather

new information on industrial energy efficiency measures. We welcome your feedback and input on the Wise Rules Tool Kit, including other rules that you have found useful and would like to share,

or requests for new Wise Rules for specific end-uses. Please phone

in your comments to the Wise Line at 1-800-459-WISE, fax them

to 703-934-3968, send them via electronic mail to:

WiseLine@ICFKaiser.com, or mail them to:

Climate Wise 

c/o ICF Kaiser Consulting Group

9300 Lee Highway

Fairfax, Virginia 22031

Information Sources

The Wise Rules Tool Kit is a compilation of some of the best information available on industrial energy efficiency. These rules are

based on energy efficiency research and engineering principles, the

experience of Climate Wise Partners, and government sources

such as the U.S. Department of Energy’s Industrial Assessment

Center (DOE/IAC) energy audit database. These resources provide a wealth of energy efficiency and other information in the

manufacturing sector, including energy, cost, and operating data.

The Wise Rules capture broad categories of efficiency improvements such as “air compressor efficiency measures” and more

detailed actions such as “optimize boiler air-to-fuel ratio.” The

Wise Rules also provide multiple perspectives on efficiency opportunities by expressing energy savings as a percent of a particular

end-use’s energy consumption (e.g., optimizing air-to-fuel ratio
Page 2 Wise Rules 1. Introduction

can reduce boiler fuel use by two to 20 percent), as a percent of a

facility’s total energy use (e.g., steam trap maintenance can reduce

a facility’s total energy use by 3.4 percent), or per unit change in a

physical parameter (e.g., for every one psi decrease in air compressor pressure, energy use is reduced by 0.7 percent). To make them

as useful as possible, the Wise Rules are presented in a variety of

formats, including graphs, bullets, and tables. In addition, we have

provided a handy reference guide to identify energy efficiency

opportunities for specific manufacturing sectors (see Appendix A).

The DOE/IAC energy audit database was an important source of

information for the Tool Kit. The database contains information

from industrial energy assessments conducted at small-to-medium

sized manufacturing facilities by teams of faculty and students

from accredited engineering schools in 30 universities across the

country. The Wise Rules Tool Kit includes information on the

expected impacts from approximately 27,000 specific improvements and upgrades from 4,300 detailed facility audits conducted

between 1990 and 1997. The majority of the auditors' recommendations had relatively short (1 to 2 year) payback periods and

were expected to be implemented within two years of the audit. 

The impacts from broad categories of efficiency recommendations

in the DOE/IAC audits are summarized in Introduction Table 1.

For example, boiler efficiency measures were recommended during 20 percent of the 4,300 audits and were expected to save on

average 2.8 percent of a facility’s total energy use, or an average of

2,600 MMBtu per year. The average cost of implementing boiler

efficiency measures was expected to be $5,300 with average firstyear savings of $7,200 for an expected average simple payback of

nine months. Compressed air efficiency measures were recommended during 68 percent of the audits. The average savings from

Introduction Table 1: Summary of Efficiency Measures from the DOE/IAC Database*

End Use Recommendation Average Average Average Average Average

Rate Annual Annual Implementation Cost Simple 

(% of audited facilities) Energy Savings Energy Savings Cost Savings Payback 

(% of total facility (MMBtu) (months)

energy use)

Boilers 20% 2.8% 2,600 $ 5,300 $ 7,200 9

Steam Systems 13% 2.0% 2,400 $ 3,300 $ 7,100 6

Furnaces & Ovens 4% 2.8% 2,500 $ 5,500 $ 8,100 8

Process Heating 1% 2.2% 3,600 $ 7,500 $ 12,200 7

Heat Containment 22% 1.5% 1,100 $ 1,100 $ 5,100 9

Heat Recovery 26% 4.6% 3,700 $ 16,500 $ 12,500 16

Cogeneration** 3% 9.1% 31,000 $667,500 $233,600 34

Air Compressors 68% 0.4% 300 $ 1,600 $ 4,300 5

Process Cooling 6% 1.1% 1,000 $ 18,900 $ 11,200 20

* Based on DOE/IAC estimates at audits of 4,300 manufacturing companies (1/90-7/97). Savings may not be additive.

**Cogeneration energy savings are based on primary fuel savings from electricity generation, including fuel inputs at off-site powerplants for purchased electricty.

Definition of Terms: The recommendation rate is equal to the number of facilities receiving a particular recommendation (e.g., repair steam leaks) divided by the total number

of facilities audited (≈4,300). Average percent energy savings are defined as the average reduction in a facility’s total energy use from a specific recommendation. Average annual

energy and cost savings reflect first year savings. Cost savings are primarily based on energy cost savings, but also may include other cost savings. The average simple payback is

the average implementation cost divided by average annual cost savings, times 12 (months per year).
air compressor efficiency measures were 0.4 percent of total facility

energy use, or an average 300 MMBtu annual reduction in each

facility’s energy use. The average cost of implementing compressed

air efficiency measures was expected to be $1,600 with average

first-year cost savings of $4,300 for an average simple payback of

five months. Similar rules developed for a range of other broad

actions as well as more detailed measures are presented in the body

of the Wise Rules Tool Kit. The estimated audit impacts for specific industry sectors are presented in Appendix A.

Using the Tool Kit

The Wise Rules were developed to help you take full advantage of

your participation in the Climate Wise Program. As you begin to

develop your Climate Wise Action Plan, the Wise Rules can help

you and your Climate Wise team generate ideas for energy savings

opportunities in your facilities. The Tool Kit provides a quick scan

of measures along a number of dimensions, including potential

energy savings, implementation costs, energy costs savings, and payback. Use the Wise Rules, along with information on the processes

in your operations, to screen a broad range of efficiency measures

and to eliminate less attractive options based on your company’s key

criteria. The Tool Kit provides background information on all of the

Wise Rules so that Climate Wise Partners will have a better understanding of how and when to use them. We have also provided 

references to the primary data source for every Wise Rule so that

partners can learn more if they desire. Appendix D of the Tool Kit

contains a summary of key references and resources.

Once measures have been identified, you can use the Wise Rules to

estimate project-level energy savings and CO2 emissions reductions

to be reported on your Climate Wise Action Plan. While you will

want to refine these estimates over time and track actual results for

completed projects, the Wise Rules can serve as place-holders until

your experience provides you with better, site-specific data. You

may also find that you want to develop your own rules based on

your engineering analyses and metered data. In this way you can

tailor Wise Rules for processes specific to your company or based

on your company’s operations, energy prices, and other factors. 

The Tool Kit also provides information required to calculate CO2

emissions reductions, as required in your Climate Wise Action

Plan. CO2 emission factors provided in Appendix B of the Tool Kit

can be used with the energy savings estimates based on the Wise

Rules to estimate total emissions reductions from your actions.

It is important to keep in mind a number of points when using

the Wise Rules:

■ The Tool Kit provides savings estimates for many important efficiency measures, but it is not a exhaustive list of

industrial efficiency opportunities. A number of processes and end-uses are not included here that may offer savings to your company (e.g., lighting and motors). There

may also be attractive measures — including pollution

prevention measures — applicable to your specific

processes and operations that your company should consider. Moreover, many of the Wise Rules reflect efficiency recommendations with relatively short (1 to 2 year)

payback periods. Your company’s payback requirement

may be longer for some types of projects. When identifying energy efficiency and pollution prevention opportunities, it is important not to limit your actions to those

measures included here.

■ The Wise Rules can provide simple savings estimates but

they cannot take the place of detailed engineering analyses based on site-specific data and operating parameters.

The Wise Rules are based on typical experience and general engineering observations from a number of sources.

The energy audit data reflect the energy and cost savings

estimates (not actual experience) across many industry

groups, over several years and across many parts of the

country. Be sure to consider your company’s unique circumstances when applying Wise Rules. For many projects, more detailed analysis will be desirable.

■ Some Wise Rules may be only applicable under specific

operating conditions (e.g., only to equipment of a certain

size or within a specific temperature range). Some efficiency measures for the same or related end-uses may

interact, such that the total energy savings from completing two measures may be less (or more) than the sum 

of the two measures’ individual impacts. Because Wise

Rules are drawn from a variety of sources, savings estimates may not be comparable, even when the energy efficiency measures are similar. For example, some Wise

Rules express savings for an energy efficiency measure on

the basis of specific equipment energy consumption,

while others are expressed as a percent of a facility’s total

energy savings. Such rules may not be comparable,

1. Introduction Wise Rules Page 3
Page 4 Wise Rules 1. Introduction

because they may assume different specific measures,

implementation levels, or contributions of the end use to

total facility energy-use. 

■ All Wise Rules are expressed as “energy savings” to allow

easy comparison across measures. However, many of the

key references and resources are based on efficiency

impacts — a closely related measure. 

■ A comprehensive analysis of efficiency opportunities

should also examine secondary impacts of savings measures. These include impacts on operations, maintenance,

productivity, and the environment. For example, changes

in boiler operating parameters may have secondary effects

on emissions of nitrogen oxides, particulates, or carbon

monoxide. These may all be important decision criteria

for your company.

■ Energy savings estimates based on the Wise Rules cannot

take the place of measuring the results of implemented

projects. For some projects, you may want to implement

energy tracking and/or metering systems to evaluate the

success of your Climate Wise efforts and the return on

your investments. This information can later be used to

develop Wise Rules for your company. 
industrial boilers can exceed 7,500 hp (250 MMBtu/hr). Typical

boiler efficiencies range from about 70 to 85 percent depending

on fuel type, configuration, and heat recovery capability.

2

Several boiler efficiency measures may be of interest to Climate

Wise Partners: boiler load management, burner replacement,

upgraded instrumentation, tune-up and air/fuel ratio optimization, stack heat loss prevention, waste heat recovery, and blowdown

control. Boiler Figure 1 illustrates the potential energy savings

from boiler efficiency measures based on IAC audit recommendations. Boiler efficiency measures with an average savings of about

three percent of facility energy use, and a simple payback of nine

months were recommended at 20 percent of the 4,300 facilities

audited. Boiler load management measures have a relatively high

2. Boilers Wise Rules Page 5

Energy Savings

Recommendation Rate

Boiler Maintenance

Boiler FIgure 1

Energy Savings from Boiler Efficiency Measures*

Recommendation Rate

Energy Savings Rate (percent of total facility energy use)

All Boiler Measures

(9 month payback)

Boiler Load Management

(23 month payback)

(5 month payback)

Combustion Air Preheating

(8 month payback)

Boiler Blowdown

(11 month payback)

0% 6% 12% 2% 4% 8% 10% 14% 16% 18% 20%

0% 2% 4% 6% 8%

* Results from the DOE/IAC Database (1/90-7/97). The IAC data reflect average potential impacts from energy efficiency measures at small-to-medium sized manufacturing

facilities across all sectors and regions of the country. Most IAC audit recommendations are expected to be implemented within two years and typically have a one-to-two year

payback period. (See Chapter 1.)

2.Boilers

Introduction

Boilers are one of the most important energy uses in manufacturing, typically comprising more than a third of total manufacturing energy demand. A boiler generates hot water or steam,

typically from the combustion of coal, oil, or natural gas. A network of pipes delivers steam (or hot water) to provide heat for a

variety of process and heating applications. Once the heat has been

extracted from the water or steam, another network of pipes

returns the condensed water back to the boiler where it is cyclically reheated. There are several different types of boilers including

natural draft, forced draft, hot water or steam, and fire tube or

water tube. The typical boiler used in small-to-medium sized

industrial operations is a forced draft steam boiler at 120-150 psi

and approximately 150 hp (equivalent to 5 MMBtu/hr).1 Large
expected energy savings, eight percent of total energy use, but

these measures were only recommended at one percent of facilities

audited and have a payback of about two years. Boiler maintenance measure were recommended at 16 percent of facilities audited with average energy savings of two percent and simple payback

time of only five months. Boiler Table 1, at the end of this chapter, summarizes the Wise Rules presented in this chapter, along

with cost savings estimates, where available.

Boiler Load Management

One of the most basic energy saving measures is effective boiler

load management — properly sizing the boiler to meet the steam

load. A good example of this is replacing a large boiler with several smaller ones, allowing for high efficiency operation during light

and full load periods. The relationship between boiler efficiency

and firing rate is non-linear. Therefore, in order to maximize overall efficiency, a boiler's output can be matched to load, based on

its design and specifications.3

Boiler Wise Rule 1

Effective boiler load management techniques, such 

as operating on high fire settings or installing smaller

boilers, can save over 7% of a typical facility’s total

energy use with an average simple payback of less

than 2 years.

4

Boiler Wise Rule 2

Load management measures, including optimal

matching of boiler size and boiler load, can save 

as much as 50% of a boiler’s fuel use.5

Tune-Up and Air/Fuel Ratio

Optimization

Periodic measurement of flue gas oxygen, carbon monoxide, opacity, and temperature provides the fundamental data required for a

boiler tune-up. It is useful to have the following instruments on

hand to best manage boiler operation: stack thermometers, fuel

meters, make-up feedwater meters, oxygen analyzers, run-time

recorders, energy output meters, and return condensate thermometers.

6 A typical tune-up might include a reduction of excess

air (and thereby excess oxygen, O2), boiler tube cleaning, and recalibration of boiler controls. Maintaining a proper air-to-fuel

ratio is very important for optimizing fuel combustion efficiency.

In a “lean” mix (high air-to-fuel ratio), heat will be lost to the

excess air, while in a “rich” mix (low air-to-fuel ratio), unburned

fuel will be emitted with the exhaust gases. Each fuel type and firing method has an optimal air/fuel ratio. For example, optimum

excess air for a pulverized coal boiler is 15 to 20 percent (3 to 3.5

percent excess O2), and optimum excess air for a forced draft gas

boiler is 5 to 10 percent (1 to 2 percent excess O2).7 The air/fuel

ratio should be set to the manufacturer’s recommendations.

Because it is difficult to reach and maintain optimal values in most

boilers, actual excess air levels may need to be set higher than optimal.8 When boilers are operating at low loads, excess-air requirements may be greater than the optimal levels and efficiency may

be lower.

9 Manual or automatic oxygen trim can ensure that the

proper air/fuel mixture ratio is maintained.10 Secondary impacts of

boiler efficiency measures should be considered when evaluating a

project. For example, adjustments of air/fuel ratio and other operating parameters may affect emissions of nitrogen oxides, particulates, or carbon monoxide. 

Boiler Wise Rule 3

An upgraded boiler maintenance program including

optimizing air-to-fuel ratio, burner maintenance, and

tube cleaning, can save about 2% of a facility’s total

energy use with an average simple payback of 5

months.11

Boiler Wise Rule 4

A comprehensive tune-up with precision testing

equipment to detect and correct excess air losses,

smoking, unburned fuel losses, sooting, and high

stack temperatures, can result in boiler fuel savings 

of 2% to 20%.12

Boiler Wise Rule 5

A 3% decrease in flue gas O2 typically produces 

boiler fuel savings of 2%.13

Boiler Wise Rule 6

Using over fire draft control systems to control excess

air can save 2% to 10% of a boiler’s fuel use with 

typical equipment costs of $1,500.14

Page 6 Wise Rules 2. Boilers
Boiler Wise Rule 7

Using a characterizable fuel valve to match the

air/fuel ratios across the load range can save 2% to

12% of a boiler’s fuel use at relatively low cost.15

Burner Replacement

The method by which fuel is delivered to the burner affects boiler

efficiency. Fuel atomization can add flexibility in fuel choice and can

improve low load operation. Atomizers suspend fine droplets of fuel

on a cone of air or steam allowing better control of fuel delivery.

16

Boiler Wise Rule 8

Converting to air or steam atomizing burners from

conventional burners can reduce boiler fuel use by 

2% to 8%.17

Stack Heat Losses and 

Waste Heat Recovery

Stack heat losses are usually the largest single energy loss in boiler operations. Key measures that minimize stack heat losses are

air/fuel ratio optimization (see above), and stack gas heat recovery for pre-heating combustion air or boiler feedwater (see

Chapter 5).18 Heat recovery may increase boiler-operating temperature, which may have secondary effects of increasing nitrogen oxide emissions. To maximize boiler efficiency and prevent

flue gas condensation, stack temperature should be 50°F to

100°F above the water temperature.

19

Boiler Wise Rule 9

Every 40°F reduction in net stack temperature (outlet

temperature minus inlet combustion air temperature)

is estimated to save 1% to 2% of a boiler’s fuel use.20

Boiler Wise Rule 10

Stack dampers prevent heat from being pulled up the

stack and can save 5% to 20% of a boiler’s fuel use.21

Boiler Wise Rule 11

Direct contact condensation heat recovery can save

8% to 20% of a boiler’s fuel use, but costs may be relatively high.22

Boiler Wise Rule 12

Preheating combustion inlet air can save about 3% of

a facility’s total energy use with an average simple payback of 8 months.23

Blowdown Control and 

Waste Heat Recovery

Dissolved and suspended solids in boiler feedwater can deposit on

heat transfer surfaces and reduce boiler efficiency. Boiler manufacturers usually establish a maximum acceptable concentration of

dissolved solids. To maintain low concentration levels, boiler water

is periodically diluted in a process called “blowdown” during

which boiler water is drained off and new water is added.24 Heat

losses during blowdown are often overlooked because they are

hard to measure and facility personnel may not fully understand

the water chemistry. Hot water drained to the sewer and excess

heat vented to the atmosphere contains unused energy.

25 Warming

make-up feedwater with blowdown waste heat can minimize heat

losses. Replacing manual blowdown valves with analyzing equipment and automatic valves can also reduce blowdown losses.

Boiler Wise Rule 13

Minimizing energy loss from boiler blowdown can

save about 2% of a facility’s total energy use with an

average simple payback of less than 1 year.

26

Boiler Wise Rule 14

Removing a 1/32 inch deposit on boiler heat transfer

surfaces can decrease a boiler’s fuel use by 2%;

removal of a 1/8 inch deposit can decrease boiler fuel

use by over 8%.27, 28

Boiler Wise Rule 15

Blowdown heat recovery is a proven technology that

can reduce a boiler’s fuel use by 2% to 5%.29

Boiler Wise Rule 16

For every 11°F that the entering feedwater temperature

is increased, the boiler’s fuel use is reduced by 1%.30

2. Boilers Wise Rules Page 7
Boiler Wise Rule 17

Changing from manual blowdown control to automatic adjustment can reduce a boiler’s energy use by

2% to 3% and reduce blowdown water losses by up

to 20%.31

Summary of Wise Rules for 

Boiler Systems

Use the Wise Rules in Boiler Table 1 (next page) to identify and

estimate potential energy saving from boiler efficiency measures. In

selecting alternative efficiency options and eliminating less attractive measures, consider the potential costs, savings, payback times

and any secondary effects. When using the Wise Rules, remember

that several of the measures may overlap, or complement each

other (e.g., tune-up and flue gas O2 reduction) and energy savings

rates of overlapping measures may not be additive. In addition,

multiple Wise Rules may address the same measure from different

perspectives. For example Boiler Wise Rule 1 expresses savings

from boiler load management as a percent of the boiler’senergy use,

while Boiler Wise Rule 2 expresses savings as a percent of the facility’s total energy use. Specific Wise Rules may not be comparable

with each other because they rely on different sources with different assumptions.

Adjust the Wise Rules in Boiler Table 1 to match your circumstances. For example, you may want to scale the gross fuel cost savings to match your boiler size. To calculate savings for a 10

MMBtu/hr natural gas boiler, multiply gross fuel cost savings by

a factor of ten. This scaling is applicable only to gross fuel cost savings expressed per MMBtu/hr, e.g., Rule 2, but not Rule 1 in

Boiler Table 1. Implementation costs may not scale in a linear

manner. Similarly, you can adjust the savings numbers on the basis

of your fuel prices and operating hours. For example, if your boiler uses coal at a price of $1.50/MMBtu, divide the cost savings

values in Boiler Table 1 by the per MMBtu price of natural gas,

e.g., $2.30, and multiply by $1.50. 

Boiler System Notes

1 Rutgers University, Office of Industrial Productivity and Energy

Assessment, Modern Industrial Assessments: A Training Manual, Version

1.0b, December 1995, p. 5-1.

2 O'Callaghan, P., Energy Management, McGraw-Hill, England, 1993, 

p. 198.

3 Taplin, H.R., Boiler Plant and Distribution System Optimization Manual,

Fairmont Press, 1991, p. 122.

4 DOE/IAC Industrial Assessment Database, July 1997.

5 Taplin, p. 122.

6 Taplin, p. 129.

7 Turner, W.C., Energy Management Handbook, 3rd Edition, Fairmont

Press, 1997, p. 90.

8 Rutgers, p. 5-12.

9 Turner, p. 90.

10 Garay, P.N., Handbook of Industrial Power and Steam Systems, Fairmont

Press, 1995, p. 211.

11 DOE/IAC Database.

12 Taplin, p. 134.

13 3M Company, “Rules of Thumb: Quick Methods of Evaluating Energy

Reduction Opportunities,” 1992, p. 8.

14 Taplin, p. 141.

15 Taplin, p. 140.

16 Taplin, p. 153.

17 Taplin, p. 153.

18 Taplin, pp. 11-18.

19 Rutgers, p. 5-12.

20 Garay, p. 219; Taplin, p. 15; Rutgers, p. 5-2.

21 Taplin, p. 15.

22 Taplin, p. 166.

23 DOE/IAC Database.

24 Garay, p. 271.

25 Taplin, p. 13.

26 DOE/IAC Database. 

27 Garay, p. 271.

28 Rutgers, p. 5-10.

29 Taplin, p. 160.

30 Taplin, p. 33.

31 Taplin, p. 161; Turner, p. 109.

Page 8 Wise Rules 2. Boilers
2. Boilers Wise Rules Page 9

a Percent of boiler energy use, unless noted.

b Energy savings are expressed as a percent of total facility energy use. Cost savings (fuel, O&M, etc.) are expressed in dollars, not in dollars per MMBtu/hr of boiler size. c Based on a natural gas boiler with 80% efficiency, operating 5,000 hrs/yr, with a gas price of ≈$2.30/MMBtu. These are gross fuel cost savings only and do not include 

capital, maintenance, or other costs or savings.

Boiler Table 1: Summary of Boiler Efficiency Measures

Source Measure Average Energy Savingsa Average Annual Cost Savings

(IAC recommendation rate) Savings per MMBtu/hr and (Payback)

All Efficiency Improvements

Implement typical efficiency 2.8% of total facility energy useb $7,200 (9 months)b

improvements, which may include 

many or all of the measures below (20%)

Boiler Load Management

Rule 1 Operate on high fire setting 7.4% of total facility energy useb $19,900 (23 months)b

or install smaller boilers (1%)

Rule 2 Optimize boiler size and boiler load 2% to 50% $230 to $5,750c

Tune-Up and Air/Fuel Ratio Optimization

Rule 3 Implement boiler maintenance (air/fuel 2.4% of total facility energy usec $2,460 (5 months)b

ratio optimization, burner maintenance, 

boiler tube cleaning) (16%)

Rule 4 Implement comprehensive tune-up 2% to 20% $230 to $2,300c

Rule 5 Decrease flue gas O2 2% per 3% decrease in O2 $230c

Rule 6 Utilize over fire draft control 2% to 10% $230 to $1,400c

Rule 7 Utilize characterizable fuel valve 2% to 12% $230 to $1,400c

Burner Replacement

Rule 8 Convert to atomizing burners 2% to 8% $230 to $920c

Stack Losses and Waste Heat Recovery

Rule 9 Reduce net stack temperature 1% to 2% per 40°F reduction $140 to $230c

Rule 10 Utilize stack dampers 5% to 20% $580 to $2,300c

Rule 11 Direct contact condensation heat recovery 8% to 20% $920 to $2,300c

Rule 12 Preheat combustion air (3%) 2.6% of total facility energy useb $5,200 (8 months)b

Blowdown Control and Heat Recovery

Rule 13 Minimize boiler blow down (1%) 1.6% of total facility energyb $8,500 (11 months)b

Rule 14 Remove deposits from heat transfer surfaces 2% for 1/32 inch deposit, $230 to $920c

8% for a 1/8 inch deposit

Rule 15 Utilize blowdown heat recovery 2% to 5% $230 to $580c

Rule 16 Preheat boiler feedwater 1% per 11°F increase $140c

Rule 17 Utilize automatic blowdown control 2% to 20% $230 to $2,300c

Source references for each Wise Rule are included in the chapter notes.
Page 10 Wise Rules 3. Steam Systems

audited with an average anticipated savings of two percent of a

facility’s total energy use and a simple payback of six months.

Improved steam line insulation was recommended at seven percent of the facilities audited with an expected average savings of

one percent of the facility’s total energy use and a simple payback

of ten months. Steam Table 2, at the end of this chapter, summarizes the Wise Rules presented in this chapter, along with cost savings estimates, where available.

Maintenance of Steam Traps

Steam traps hold steam in the coil until the steam releases its heat

energy and condenses. Steam trap operation can be checked by

comparing the temperature on each side of the trap. In properly

Energy Savings

Recommendation Rate

Repair Steam Leaks

Steam Figure 1

Energy Savings from Steam System Efficiency Measures*

Recommendation Rate

Energy Savings Rate (percent of total facility energy use)

All Steam Measures

(6 month payback)

Steam Trap Maintenance

(2 month payback)

(3 month payback)

Insulate Steam Lines

(10 month payback)

Condensate Measures

(8 month payback)

0% 1% 2% 3% 4% 5% 6% 7% 8% 9% 10% 13%

0% 1% 2% 3% 4%

11% 12%

3.Steam Systems

Introduction

Steam system efficiency improvements are a logical complement

to boiler efficiency measures. Useful energy escapes from steam

distribution systems from malfunctioning steam traps, steam

leaks, and via radiative losses from steam lines, condensate lines,

and storage tanks. Each of these areas presents opportunities for

energy savings.

Steam system efficiency measures that may be of interest to

Climate Wise Partners include: steam trap maintenance, repairing

steam leaks, insulation, condensate measures, and vapor recompression. Steam Figure 1 illustrates the potential energy savings

from steam system efficiency measures based on specific recommendations in the DOE/IAC database. Steam system efficiency

measures were recommended at 13 percent of the 4,300 facilities

* Results from the DOE/IAC Database (1/90-7/97). The IAC data reflect average potential impacts from energy efficiency measures at small-to-medium sized manufacturing

facilities across all sectors and regions of the country. Most IAC audit recommendations are expected to be implemented within two years and typically have a one-to-two year

payback period. (See Chapter 1.)
3. Steam Systems Wise Rules Page 11

functioning steam traps, there will be a large temperature difference between the two sides of the trap and no steam downstream

of the trap. Malfunctioning steam traps waste steam and result in

higher boiler fuel consumption.1 Typically, 15 to 60 percent of the

steam traps in a plant may be malfunctioning and wasting large

amounts of energy.

2

Steam Wise Rule 1

An effective steam trap maintenance program can 

save 3% of a facility’s total energy use with an average

simple payback of 2 months.3

Steam Wise Rule 2

An effective steam trap maintenance program can

reduce a boiler’s fuel use by 10% to 20%.4

Reducing Leaks 

Repairing leaks in steam pipes, condensate return lines, and fittings can yield significant energy and cost savings. Steam leaks

increase boiler fuel use because additional steam must be generated to make up for the wasted steam. Leaky condensate return lines

increase make-up water requirements and increase boiler fuel use

because more energy is required to heat the cooler, make-up 

boiler feedwater than would be required to heat the returned condensate. Actual savings will depend on boiler efficiency, steam

pressure, and annual operating hours.5

Steam Wise Rule 3

Repairing steam system leaks can save 1% of a 

facility’s total energy use with an average simple 

payback of 3 months.6

Steam Wise Rule 4

A single high-pressure steam leak (125 psi) can result

in energy losses costing from $660 to $2,200 per year

(8,760 hrs). A single low-pressure steam leak (15 psi)

can result in energy losses costing $130 to $480 per

year (8,760 hrs).7

Reducing Heat Losses

Often boiler and steam system insulation is removed to make

repairs and is not replaced. Uninsulated surfaces in boiler and

steam systems can reach 450°F. Such high temperatures can

threaten employee safety and can pose a fire hazard, as well as

waste significant amounts of energy.

Steam Wise Rule 5

Insulating steam lines can save 1% of a facility’s total

energy use with an average simple payback of 10

months.9

Vapor Recompression

When there is a need for low pressure steam, vapor recompression

can double the pressure of vented steam using only a fraction of

the energy required to generate the steam in a boiler.

10

Steam Wise Rule 6

Vapor recompression saves 90% to 95% of the energy

needed to raise the steam to the same pressure in a

boiler.

11

Condensate

A number of measures can be implemented to reduce heat losses

from condensate — the water that forms after steam has been

used. Increasing the amount of condensate returned to the boiler

saves energy because it eliminates the need to heat cold make-up

water. Insulating steam lines, condensate lines and tanks, will preSteam Table 1 

Annual Costs of Heat Loss per 100 feet of

Uninsulated Steam Pipe8

Steam Pressure Cost per 100 ft of

pipe per year (8,760 hr)

25 psi $1,600

50 psi $1,900

75 psi $2,100

100 psi $2,300
vent unnecessary heat loss through the system. Collecting highpressure condensate after flash steam formation can provide lowpressure steam for other purposes.

Steam Wise Rule 7

Measures to reduce heat loss from condensate in a

steam system can save over 1% of a facility’s total energy use with an average simple payback of 8 months.12

Summary of Wise Rules for 

Steam Systems

Use the Wise Rules in Steam Table 2 (next page) to identify and

estimate potential energy saving from steam system efficiency

measures. When identifying attractive options and eliminating

weak ones, consider potential costs, savings, payback periods and

any secondary effects. When using the Wise Rules, remember that

some measures may interact or complement each other (e.g.,

steam trap maintenance and steam pipe insulation) and energy

savings rates may not be additive. Multiple Wise Rules may

address the same efficiency measure from different perspectives.

For example, Steam Rules 1 and 2 express savings from steam trap

maintenance as (1) a percent of a facility's total energy use, and (2)

as a percent of boiler energy use.

Steam System Notes

1 Rutgers University Office of Industrial Productivity and Energy

Assessment, Modern Industrial Assessments: A Training Manual, Version

1.0b, December 1995, p. 5-19.

2 Turner, W.C., Energy Management Handbook, 3rd Edition, Fairmont Press,

1997, p. 149.

3 DOE/IAC Industrial Assessment Database, July 1997.

4 Taplin, H.R., Boiler Plant and Distribution System Optimization Manual,

Fairmont Press, 1991, p. 276.

5 Rutgers, p. 5-17.

6 DOE/IAC Database.

7 Rutgers University OIPEA, “Useful Rules of Thumb for Resource

Conservation and Pollution Prevention,” March 1996, #1 and #2.

8 Rutgers, “Useful Rules of Thumb,”#8.

9 DOE/IAC Database.

10 Bonneville Power Administration (BPA), Washington State Energy Office,

Electric Ideas Clearinghouse, “Vapor Recompression,” July 1992, p. 1.

11 BPA, p. 1.

12 DOE/IAC Database.

Page 12 Wise Rules 3. Steam Systems
Steam Table 2: Summary of Steam System Efficiency Measures

Source Measure Average Energy Savings Average Annual Cost Savings

(IAC recommendation rate) (payback)

All Efficiency Improvements

Implement typical efficiency 2% of total facility energy use $7,100 (6 months)

improvements, which may include 

many or all of the measures below (13%)

Steam Trap Maintenance

Rule 1 Implement steam trap 3.4% of total facility energy use $17,400 (2 months)

maintenance program (1%)

Rule 2 Implement steam trap maintenance program 10% to 20% of boiler fuel use 10% to 20% of boiler fuel costs

Leak Repair

Rule 3 Repair steam leaks (2%) 1.0% of total facility energy use $6,100 (3 months)

Rule 4 Repair high pressure leaks (125 psi) $660 to $2,200 per leak 

Repair low pressure leaks (15 psi) $130 to $480 per leak

Insulation

Table 1 Insulate steam lines (7%) $1,600 to $2,300 per 100 feet

Rule 5 Improve steam line insulation 1.0% of total facility energy use $2,800 (10 months)

Other Measures

Rule 6 Recompress low pressure steam 90% to 95% of energy needed to 

raise the steam in a boiler

Rule 7 Reduce heat loss from condensate (4%) 1.3% of total facility energy use $6,700 (8 months)

3. Steam Systems Wise Rules Page 13

Source references for each Wise Rule are included in the chapter notes.
Page 14 Wise Rules 4. Process Heating

Energy 

Savings

Recommendation 

Rate

Process Heating Figure 1

Energy Savings from Process Heating Efficiency Measures*

Energy Savings Rate (percent of total facility energy use)

All Furnace Heating Measures

(8month payback)

All Process Heating Measures

(7 month payback)

Recommendation Rate

0% 1% 2% 3% 4%

0% 1% 2% 3% 5%

Oven/Kiln Heat Recovery

(16 month payback)

4%

4.ProcessHeating

Introduction

I

ndustrial companies use furnaces, ovens, and kilns to raise the

temperature of a raw material or intermediate product as part of

a manufacturing process. Important process heating efficiency

measures include: insulation, combustion air control, burner

adjustment, automatic stack dampers, waste heat recovery, temperature optimization, use of minimum safe ventilation, immersion heating, and enhanced sensitivity of temperature control and

cutoff. Minimizing equipment heat-up time can also save energy.

For example, many ovens need only 15 to 60 minutes to heat up,

1

but, in practice, may “warm up” for an unnecessarily long period

of time. The remainder of this chapter provides additional information on heat containment, process heating and direct heating. 

Process Heating Figure 1 illustrates the potential energy savings

from heating efficiency measures based on IAC audit recommendations. Furnace efficiency measures were recommended at four

percent of the facilities audited with estimated average savings of

three percent of the average facility’s total energy use and a simple

payback of eight months. Heat recovery from ovens, kilns, and

other equipment was recommended during only one percent of

* Results from the DOE/IAC Database (1/90-7/97). The IAC data reflect average potential impacts from energy efficiency measures at small-to-medium sized manufacturing

facilities across all sectors and regions of the country. Most IAC audit recommendations are expected to be implemented within two years and typically have a one-to-two year

payback period. (See Chapter 1.)

the audits with estimated energy savings of almost five percent and

average simple payback of 16 months. Process Heating Table 1,

at the end of this chapter, summarizes the Wise Rules presented in

this chapter, along with cost savings estimates, where available.

Insulation and Heat Containment

Heat loss can cause major reductions in process heating efficiency.

Heat containment measures include insulation of bare equipment

and open tanks, isolating hot or cold equipment from air conditioned areas, and reducing infiltration into hot or cold process

equipment. New refractory fiber material, with low thermal conductivity and heat storage, can produce significant improvements

in efficiency with minimal detriment to the work environment.

Typical applications include furnace covers, installing fiber liner

between the standard refractory lining and the shell wall, or

installing ceramic fiber linings over the present refractory liner.

Replacing standard refractory linings with vacuum-formed refractory fiber insulation can also improve efficiency.

2
Process Heating Wise Rule 1

Proper heat containment can save about 2% of a

facility’s total energy use with an average simple 

payback of 9 months.3

Process Heating Wise Rule 2

Insulating a furnace with refractory fiber liners can

improve the thermal efficiency of the heating process

by up to 50%.4

Combustion Air Control

Maintaining a proper air-to-fuel ratio is very important for optimizing fuel combustion efficiency in process heating. In a “lean”

mix (high air-to-fuel ratio), heat will be lost to the excess air, while

in a “rich” mix (low air-to-fuel ratio), unburned fuel will be emitted with the exhaust gases. Aspirators can help maintain a proper

air-to-fuel ratio for premix burners systems, while ratio-regulating

systems can do this for nozzle mix burners.5 Automatic burner

control is also an effective strategy for optimizing the air-to-fuel

ratio. Control systems technologies include programmable logic

controllers, direct stack temperature monitors, and intelligent

high-level computer controllers.6 Be sure to consider potential secondary impacts from adjustments of air/fuel ratio or other operating parameters, such as changes in emissions of nitrogen oxides,

particulates, and carbon monoxide.

Process Waste Heat Recovery

Exhaust gas heat losses are another source of process efficiency

loss. Heat recovery systems can recapture this heat and reintroduce it into processing heat or other end-uses. A recuperator

extracts heat from furnace waste gases to preheat incoming combustion air. A regenerator uses porous ceramic beds for waste gas

heat recovery and short-term heat storage.

7 Chapter 5, “Waste

Heat Recovery and Cogeneration,” describes additional waste

heat recovery measures. 

Process Heating Wise Rule 3

Recovering waste heat from furnaces, ovens, kilns,

and other equipment can save 5% of a typical facility’s

total energy use with an average simple payback of

16 months.8

Process Heating Wise Rule 4

Recovering waste heat through a recuperator can

reduce a kiln’s energy use by up to 30%; regenerators

can save up to 50%.9,10

Specific Process Heat Applications

Energy savings opportunities available in some sectors may be

more broadly applicable. For example, in the lumber industry, airdrying lumber before putting it in the kiln can reduce kiln energy

use. Using variable speed controls to reduce kiln fan power after

the water has been driven off can significantly reduce kiln energy

use without affecting drying time or product quality.

11 In the

cement industry, advanced control systems such as automated

controls and expert systems have shown significant energy savings.

Optimizing heat transfer conditions in the clinker cooler through

better distribution of clinker and air can also result in substantial

energy savings.

Process Heating Wise Rule 5

Each percent of moisture removed by air drying 

lumber reduces the kiln’s energy use by 50 to 85 Btu

per board foot.12

Process Heating Wise Rule 6

Variable fan speed control in the lumber industry 

can reduce dry kiln airflow by 20% and reduce the

kiln’s energy used during surface drying by as much 

as 50%.13

Process Heating Wise Rule 7

Installing expert systems for kiln secondary control

can reduce a cement kiln’s energy use by up to 3%.14

Process Heating Wise Rule 8

New clinker cooler technologies that optimize heat

transfer conditions can reduce a cement kiln’s energy

use by up to 6%.15

4. Process Heating Wise Rules Page 15
Direct Heating

Direct heating is generally more efficient than indirect heating

because heat transfer losses from equipment and transfer media

are eliminated. Examples of direct heating technologies include

direct firing (generally with natural gas), infrared, microwave,

and dielectric heating. Direct heating also provides other operational benefits including faster drying times, reduced maintenance, easier installation, more precise temperature control,

more uniform heating, and increased output.16

Process Heating Wise Rule 9

Direct firing with natural gas in place of indirect

steam heating has the potential to save 33% to 45%

of process heating energy use. Payback times may range

from a few months to 6 years.17

Process Heating Wise Rule 10

Direct electric heating (infrared, microwave, or dielectric) can reduce process heating energy use by up to

80% with typical payback periods of 1 to 3 years.18

Summary of Wise Rules for

Process Heating

Use the Wise Rules in Process Heating Table 1 (next page) to

identify and estimate potential energy savings from process heating efficiency measures. When evaluating alternatives and eliminating options, consider the potential costs, energy savings, payback time, and any secondary effects. When using the Wise

Rules, remember several of the measures may overlap or complement each other and energy savings rates from overlapping measures may not be additive. In addition, multiple Wise Rules may

express savings for similar measures from different perspectives.

For example, some express energy savings in terms of a typical

facility’s total energy use, while others are expressed in terms of

an end use’s energy consumption. 

Page 16 Wise Rules 4. Process Heating

Process Heating Notes

1 3M Company, “Laboratory Operations Energy Efficiency Guidelines,” 

Feb. 1994.

2 Rutgers University Office of Industrial Productivity and Energy 

Assessment, Modern Industrial Assessments: A Training Manual, Version 

1.0b, December 1995, p. 5-36.

3 DOE/IAC Industrial Assessment Database, July 1997.

4 Rutgers, p. 5-37.

5 Rutgers, p. 5-34.

6 Centre for the Analysis and Dissemination of Demonstrated Energy

Technologies (CADDET), “Learning from Experiences with Process

Heating in the Metals Industry,” Analyses Series No. 11, 1990.

7 CADDET, 1990.

8 DOE/IAC Database. 

9 Bonneville Power Administration (BPA), Washington State Energy Office,

Electric Ideas Clearinghouse, “Dry Kiln Retrofit/Replacement,” October

1991.

10 CADDET, 1990.

11 BPA, “Dry Kiln Retrofit/Replacement.”

12 Bonneville Power Administration (BPA), Washington State Energy Office,

Electric Ideas Clearinghouse, “Optimizing Dry Kiln Operation,” October

1991.

13 BPA, “Dry Kiln Retrofit/Replacement.”

14 ICF Kaiser Consulting Group estimate based on cement industry data.

15 ICF Kaiser Consulting Group estimate based on cement industry data.

16 Mercer, A., Learning from Experience with Industrial Drying Technologies,

Centre for the Analysis and Dissemination of Demonstrated Energy 

Technologies (CADDET), 1994.

17 Mercer, pp. 25-38.

18 Mercer, pp. 39-54.
4. Process Heating Wise Rules Page 17

Process Heating Table 1: Summary of Process Heating Efficiency Measures

Source Measure Average Energy Savings Average Annual Cost Savings

(IAC recommendation rate) (payback)

All Efficiency Improvements

Implement typical efficiency 2.8% of total facility energy use $8,100 (8 months)

improvements, which may include 

many or all of the measures below (4%)

Insulation and Heat Containment

Rule 1 Improve heat containment (22%) 1.5% of total facility energy use $5,100 (9 months) 

Rule 2 Install fiber insulation 50% improvement in thermal efficiency

Process Heating Waste Heat Recovery

Rule 3 Recover furnace, oven, and kiln 4.6% of total facility energy use $13,000 (16 months)

waste heat (1%)

Rule 4 Recover heat from kilns 30% to 50% reduction in kiln energy use

Specific Process Heating Applications

Rule 5 Air dry lumber 50 to 85 Btu per board foot for each 

1% moisture removed

Rule 6 Install variable speed drives (VSD) up to 50% of kiln energy use

for dry kiln airflow

Rule 7 Install expert systems for up to 3% of cement kiln 

secondary kiln controls energy use

Rule 8 Optimize heat transfer conditions up to 6% of cement kiln energy use

Direct Heating

Rule 9 Use direct firing with natural 33% to 45% of the energy (few months to 6 years)

gas in place of indirect heating requirement

Rule 10 Use direct electric heating in 80% of heating energy use (1 to 3 years)

place of indirect heating

Source references for each Wise Rule are included in the chapter notes.
fuel inputs at off-site powerplants for purchased electricity) and the

payback was about three years. Heat Recovery/Cogen Table 2, at

the end of this chapter, summarizes the Wise Rules presented in

this chapter, along with cost savings estimates, where available.

Waste Heat Recovery

Heat recovery is often a viable retrofit option for existing equipment.

Ventilation and exhaust from process heating or combustion equipment are some common sources of potentially recoverable energy.

Heat recovery is beneficial only if the heat can be used elsewhere and

if it is available when it is needed. Typical applications of waste heat

include process heating, combustion air preheating, boiler feedwater

preheating, and space heating.1 Be sure to consider any secondary

effects from adjustments of combustion parameters, such as emissions of nitrogen oxides, particulates, and carbon monoxide.

Page 18 Wise Rules 5. Heat Recovery & Cogeneration

Energy 

Savings

Recommendation 

Rate

Heat Containment

Heat Recovery/Cogen Figure 1

Energy Savings from Heat Recovery and Cogeneration Efficiency Measures*

Recommendation Rate

Energy Savings Rate (percent of total facility energy use)

Waste Heat Recovery

(16 month payback)

Cogeneration**

(34 month payback)

(9 month payback)

0%

0%

3% 6% 9% 12% 15% 18% 22% 24% 24% 26%

2% 4% 6% 8% 10%

* Results from the DOE/IAC Database (1/90-7/97). The IAC data reflect average potential impacts from energy efficiency measures at small-to-medium sized manufacturing

facilities across all sectors and regions of the country. Most IAC audit recommendations are expected to be implemented within two years and typically have a one-to-two year

payback period. (See Chapter 1.)

** Cogeneration energy savings are based on primary fuel savings from electricity generation, including fuel inputs at off-site powerplants for purchased electricity. Off-site power generation is assumed to have a heat rate of about 10,000 Btu/kWh. Savings are calculated by dividing total energy savings, including powerplant inputs, by total facilityenergy use.

Introduction

Heat exchangers recover useful energy that would ordinarily be

lost. Generally, a heated gas or liquid leaving a process passes

through a heat exchanger to preheat another gas or liquid entering

a process or an HVAC system. Cogeneration takes heat recovery a

step further by recovering heat that would normally be wasted in

the process of power generation and steam production.

Cogeneration systems can reach efficiencies that can triple, or even

quadruple, conventional power and steam generation. Heat

Recovery/Cogen Figure 1 illustrates the potential energy savings

from heat recovery and cogeneration measures based on IAC audit

recommendations. Waste heat recovery measures were recommended at 26 percent of the 4,300 IAC audits conducted from

1990 through mid-1997 and were estimated to save almost five

percent of the average facility’s total energy use with a simple payback of 16 months. Cogeneration was recommended at fewer facilities (three percent), but the average expected energy savings were

much higher (nine percent of the facility’s energy use, including

5. WasteHeatRecovery andCogeneration
Heat Recovery/Cogen Wise Rule 1

Recovering waste heat can reduce a typical facility’s

total energy use by about 5% with an average simple

payback of 16 months.2

Heat Recovery/Cogen Wise Rule 2

Reducing net stack temperature (outlet temperature

minus inlet combustion air temperature) by 40°F is

estimated to reduce the boiler’s fuel use by 1% to 2%.3

Heat Recovery/Cogen Wise Rule 3

Preheating furnace combustion air with recovered

waste heat can save up to 50% of the furnace’s energy

use. Heat Recovery/Cogen Table 1 summarizes typical fuel savings for a natural gas furnace.4

Air-to-air heat exchangers transfer heat from a hot air stream to a

cold one. Using air-to-air heat exchangers to preheat ventilation

air in the winter or for precooling in the summer can add to the

air distribution system’s pressure losses and may require larger ventilation fans.6 In heat pipes, hot and cold air streams flow in opposite directions. Heat pipes typically are used in the range of 150°F

to 850°F and recover between 60 and 80 percent of the heat from

the exhaust air stream. Heat wheels are porous disks with high

heat capacity that rotate between a cold-gas duct and a hot-gas

duct. They can recover from 70 to 90 percent of the heat from the

exhaust air stream. Glass fiber ceramic heat wheels can be used at

temperatures up to 2,000°F.

7 Economizers are used primarily to

preheat boiler feedwater with flue gas waste heat. The boiler feedwater flows through the economizer and is heated by the hot

exhaust gases from the boiler. The higher the waste gas temperature, the greater the possible energy savings. Economizers can be

used at gas temperatures up to 1,800°F.

8

Heat Recovery/Cogen Wise Rule 4

Using an economizer to capture flue gas waste heat

and preheat boiler feedwater can reduce a boiler’s fuel

use by up to 5%.9

Heat exchanger efficiency is directly proportional to the surface

area that separates the heated and cooled fluids. If heat exchanger

surfaces become fouled with films, deposits, or corrosion,

exchanger efficiency suffers. If heavy fouling is expected, contaminated streams may need to be filtered, or the design may need to

be modified to include different materials or to allow easy access

to surfaces for frequent cleaning.10

Heat Recovery/Cogen Wise Rule 5

Removing a 1/32 inch deposit on boiler’s heat transfer

surfaces can reduce a boiler’s energy use by 2%;

removing a 1/8 inch deposit can reduce a boiler’s

energy use by over 8%.11,12

Cogeneration

Cogeneration is the simultaneous production of electric power

and thermal energy from a single fuel. In a typical configuration,

an industrial boiler is replaced by a gas turbine. The turbine is

used to generate electricity, and the waste heat is used to generate

steam in a heat recovery steam generator (or HRSG). Other

cogeneration configurations combine boilers and steam turbines,

or gas turbines and steam turbines (combined cycle units). Two

emerging technologies that are applicable to cogeneration are the

use of fuel cells and the Kalina cycle — a vapor heat engine cycle

using an ammonia-water working fluid.13

Cogeneration is often a more efficient way of providing electricity and process heat than producing them independently given the

overall efficiency gain, as well as a potential fuel shift. Average efficiencies for traditional cogeneration systems can range from 70

5. Heat Recovery & Cogeneration Wise Rules Page 19

Heat Recovery/Cogen Table 1

Fuel Savings from Preheating Combustion Air5

Furnace Outlet Combustion Air Preheat Temperature 

Temperature 400°F 600°F 800°F 1000°F 1200°F

2600°F 22% 30% 37% 43% 48%

2400°F 18% 26% 33% 38% 43%

2200°F 16% 23% 29% 34% 39%

2000°F 14% 20% 26% 31% 36%

1800°F 13% 19% 24% 29% 33%

1600°F 11% 17% 22% 26% 30%

1400°F 10% 16% 20% 25% 28%

Based on a natural gas furnace with 10% excess air.
Page 20 Wise Rules 5. Heat Recovery & Cogeneration

percent to more than 80 percent.

14 Cogeneration makes most

sense in facilities where steam and electrical demand are balanced

with the typical output of the cogeneration unit.

There are generally economies of scale involved with cogeneration

systems, with larger units having lower costs (per installed kW)

and higher efficiencies. Average-sized cogeneration units range

from 10 to 50 MW, though units as small as 3 MW can be costeffective.

15 Cogeneration economics depend on system utilization.16 Therefore, it is important to closely match the system’s 

output to the facility’s steam and electrical load. When electricity

production is in excess of on-site consumption needs, it can typically be sold to others and should be accounted for when evaluating the feasibility and economics of cogeneration. It is a good idea

to examine the steam load prior to assessing electrical needs in

evaluating a potential cogeneration project. Be sure to consider

any secondary impacts from new combustion equipment such as

nitrogen oxide emissions from gas turbines. 

Heat Recovery/Cogen Wise Rule 6

Gas turbines with heat recovery equipment typically

cost from $600 to $1,000/kW. Larger gas turbines

may be available for half the cost per kW.

17

Heat Recovery/Cogen Wise Rule 7

A typical cogeneration project may reduce primary

energy consumption (including fuel inputs at off-site

powerplants for purchased electricity) for steam and

electricity generation by 10% to 15%.18

Heat Recovery/Cogen Wise Rule 8

Cogeneration systems can save about 9% of a typical

facility’s primary fuel inputs for on-site energy use

(i.e., including fuel savings at off-site powerplants for

purchased electricity) with an average simple payback

of 34 months.19 (Savings are calculated by dividing

total energy savings, including powerplant inputs, by

total facility energy use.)

Summary of Wise Rules for Waste

Heat Recovery and Cogeneration

Use the Wise Rules in Heat Recovery/Cogen Table 2 (next page) to

identify and estimate potential energy saving from heat recovery and

cogeneration. Consider potential costs, savings, payback time, and

any secondary effects in order to analyze different efficiency alternatives and eliminate less attractive options. When using the Wise

Rules, remember that several of the measures may interact or complement each other and energy savings rates may not 

be additive.

Waste Heat Recovery and Cogeneration Notes

1 Rutgers University Office of Industrial Productivity and Energy

Assessment, Modern Industrial Assessments: A Training Manual, Version

1.0b, December 1995, pp. 5-21 and 5-22.

2 DOE/IAC Industrial Assessment Database, July 1997.

3 Garay, P.N., Handbook of Industrial Power and Steam Systems, Fairmont

Press, 1995, p. 219; Taplin, H.R., Boiler Plant and Distribution System

Optimization Manual, Fairmont Press, 1991, p. 15; Rutgers, p. 5-2.

4 Rutgers, p. 5-21.

5 Rutgers, p. 5-21.

6 Bonneville Power Administration (BPA), Washington State Energy Office,

Electric Ideas Clearinghouse, “Exhaust Air Heat Recovery Systems,” May

1992, p. 1.

7 Rutgers, p. 5-23.

8 Rutgers, p. 5-22.

9 O'Callaghan, P., Energy Management, McGraw-Hill, England, 1993, 

p. 198.

10 Turner, W.C., Energy Management Handbook, 3rd Edition, Fairmont Press,

1997, pp. 207-208.

11 Garay, p. 271.

12 Rutgers, p. 5-10.

13 Orlando, J.A., Cogeneration Design Guide, American Society of Heating,

Refrigerating and Air-Conditioning Engineers, Inc., 1996, pp. 62-63.

14 Stromberg, Jan, Gas-Turbine-Based CHP in Industry, Centre for the

Analysis and Dissemination of Demonstrated Energy Technologies (CAD

DET), 1993, p. 6.

15 McIntire, Margaret E., “Trigen Dispersed Energy Services for the MidSized Industrial and Commercial Market,” Nineteenth National Industrial

Energy Technology Conference Proceedings, 1997, pp. 117-124.

16 Payne, F.W., Cogeneration Management Reference Guide, Fairmont Press,

Inc., 1997, p. 6.

17 Rutgers, p. 5-40.

18 ICF Kaiser Consulting Group estimate.

19 DOE/IAC database. Off-site power generation is assumed to have a heat

rate of about 10,000 Btu/kWh.
Heat Recovery/Cogen Table 2: Summary of Heat Recovery and Cogeneration Efficiency Measures

Source Measure Average Energy Savings* Average Annual Cost Savings

(IAC recommendation rate) (payback)

Waste Heat Recovery

Rule 1 Recover waste heat (26%) 4.6% of total facility energy use $12,500 (16 months)

Rule 2 Reduce stack waste heat losses 1% to 2% per 40°F reduction

Rule 3 Preheat furnace combustion air Up to 50%

Rule 4 Preheat boiler feedwater up to 5% of boiler energy use

Rule 5 Clean heat exchangers 2% for 1/32 inch deposit,

8% for a 1/8 inch deposit

Cogeneration

Rule 6 Install gas turbine cogeneration Capital Cost: $600-$1,000/kW

Rule 7 Install cogeneration system 10% to 15% of primary energy consumption

Rule 8 Install cogeneration system (3%) 9.1% of total facility energy use** $233,600 (34 months)

Source references for each Wise Rule are included in the chapter notes.

* Percent of equipment energy use, unless noted.

** Cogeneration energy savings are based on primary fuel savings from electricity generation, including fuel inputs at off-site powerplants for purchased electricity. Off-site 

power generation is assumed to have a heat rate of about 10,000 Btu/kWh. Savings are calculated by dividing total energy savings, including powerplant inputs, by total 

facility energy use.

5. Heat Recovery & Cogeneration Wise Rules Page 21
Page 22 Wise Rules 6. Compressed Air Systems

Several compressed air system efficiency measures may be of interest to Climate Wise Partners, including using cooler intake air,

optimizing load, reducing pressure, eliminating or reducing air

use, repairing leaks, recovering waste heat, replacing filters, and

cleaning coolers. Typical energy savings for these types of air compressor measures are illustrated in Compressed Air Figure 1, based

on specific recommendations in the DOE/IAC database. Air compressor efficiency measures can be made at most facilities and were

Energy Savings

Recommendation Rate

Upgrading Screw 

Compressor Controls

Compressed Air Figure 1

Energy Savings from Air Compressor Efficiency Measures*

Energy Savings Rate (percent of total facility energy use)

Entire Compressed Air System

(5 month payback)

Using Cooler Intake Air

(5 month payback)

(8 month payback)

Compressor Pressure 

Reduction

(4 month payback)

Eliminating or Reducing 

Compressed Air Use

(6 month payback)

Recommendation Rate

0% 10% 20% 30% 40% 50% 60% 70%

0%

Repairing Air Leaks

(3 month payback)

Air Compressor Waste 

Heat Recovery

(10 month payback)

0.3% 0.6% 0.9% 1.2% 1.5% 1.8%

6.Compressed Air Systems

Introduction

Compressed air is used to power tools and machines, to regulate HVAC systems, and for drying or cleaning various items.

The two main types of air compressors are reciprocating compressors and screw compressors. Screw compressors generally use

more energy than reciprocating compressors, especially when

they are oversized. Compressor energy use is a function of many

variables including compressor type, part-load efficiency, and

control mechanisms.1

* Results from the DOE/IAC Database (1/90-7/97). The IAC data reflect average potential impacts from energy efficiency measures at small-to-medium sized manufacturing

facilities across all sectors and regions of the country. Most IAC audit recommendations are expected to be implemented within two years and typically have a one-to-two year

payback period. (See Chapter 1.)
recommended at 68 percent of the 4,300 IAC audits conducted

from 1990 to mid-1997. Using cooler intake air and repairing air

leaks were recommended at more than a third of facilities audited.

Average expected savings are relatively small — less than a half

percent of a facility’s total energy use. However, these measures

tend to have relatively short payback periods (about 5 months)

and reduce electricity use, a relatively expensive energy source with

high CO2 emission rates in many regions. Some measures have

higher impacts. For example, air compressor waste heat recovery

can reduce facility energy use by almost two percent. Compressed

Air Table 2, at the end of this chapter, summarizes the Wise Rules

presented in this chapter, along with cost savings estimates, where

available. 

The range of compressor efficiency measures is broad. Air compressor energy use may represent 5 to 15 percent of a typical facility’s energy use, depending upon process needs.

Compressed Air Wise Rule 1

Efficiency improvements can reduce compressed air

system energy use by 20% to 50%.2

Compressed Air Wise Rule 2

Efficiency improvements to compressed air systems

can save approximately one-half percent of a facility’s

total energy use.3

Use Cooler Intake Air 

The amount of energy required to compress air is a function of the

intake air temperature, with warm air requiring more energy to

compress than cool air. There is a potential for energy savings

when cooler air, typically from outside, is used in place of warmer

compressor room air. Often piping can be installed to supply cooler outside air to the compressor intake. Energy and cost savings

for this measure will depend on compressor size, load factor, and

the number of hours of operation.4

Compressed Air Wise Rule 3

Using cooler intake air for compressors can reduce

compressed air system energy use by 1% per 5°F reduction in intake air temperature.5 The payback period

for this measure is usually less than two years.

6

Compressed Air Wise Rule 4

Using cooler intake air for compressors can save

almost one-half percent of a facility’s total energy use

with an average simple payback of 5 months.7

Match Compressor with 

Load Requirement

Matching the compressor size with load can result in significant

energy savings. Because air compressors can consume 16 to 100 percent of full load power at low loads, it is a good idea to optimize

compressor loading to minimize operation at low output levels.8

This optimization can be achieved with unloading controls, automatic shutdown timers, and manual or automatic compressor

sequencing. Unloading controls cost about $500 to install at the

factory and about $1,000 to retrofit; automatic on/off timers cost

about $300 to install. You might also consider purchasing a small

compressor for smaller loads to avoid low-load operation of a large

compressor.

9

Compressed Air Wise Rule 5

Installing or adjusting unloading controls can reduce

compressed air system energy use by about 10%.10

Compressed Air Wise Rule 6

Upgrading controls on screw air compressors can

reduce a facility’s total energy use by about 1% with

an average simple payback of 8 months.11

Reduce Compressor Air Pressure

Air is often compressed to a higher pressure than required by the

process equipment. Lowering air pressure reduces compressor

demand and energy use. Be sure to determine the minimum

required pressure before implementing this measure. Consider

reducing compressor operating pressure if it is higher than 10 psi

above that required by the process equipment (except with long

delivery lines or high pressure drops).12 Energy savings depend on

the compressor type, power rating, load factor, use factor, horsepower reduction factor, and the proposed pressure change.13

6. Compressed Air Systems Wise Rules Page 23
Page 24 Wise Rules 6. Compressed Air Systems

Compressed Air Wise Rule 7

Reducing air compressor pressure can reduce a facility’s total energy use by about one-half percent with an

average simple payback of 4 months.14

Compressed Air Wise Rule 8

Reducing air compressor pressure by 2 psi can reduce

compressor energy use by 1% (at 100 psi).15

Reduce or Eliminate 

Compressed Air Use

In some facilities, compressed air use can be reduced or eliminated

entirely. Less expensive alternatives may exist for processes such as

cooling, agitating liquids, or moving products. In addition, some

air-powered tools (e.g., grinders) can be replaced by high frequency electric tools. Reducing compressed air use may result in an existing compressor operating at reduced load and lower efficiency. If

the reductions are significant, you may need to re-optimize loading

sequence or controls, or change to a smaller compressor.

Compressed Air Wise Rule 9

Eliminating or reducing compressed air usage for certain activities can reduce a facility’s total energy use by

more than one-half percent, with an average simple

payback of 6 months.16

Eliminate Air Leaks

Compressed air distribution system leaks along piping, around

valves, fittings, flanges, hoses, traps, and filters can result in significant energy losses in manufacturing facilities. Typical leakage rates

range from two to 20 percent of system capacity. In poorly maintained systems, leakage rates can be as high as 40 percent.17 The

cost of compressed air leaks increases exponentially as the size of the

hole increases. Compressed Air Table 1 presents average energy

losses for air leaks of various sizes. Leaks are often audible when the

system is pressurized but equipment is not running (e.g., during

breaks or after hours). Where you suspect a slow leak, use a soapy

water solution or an ultrasonic detector to pinpoint its location.18

When repairing compressed air leaks, it is important to consider

the effect on compressor loading. If the reductions are significant,

you may need to re-optimize loading sequence or controls.

Compressed Air Wise Rule 10

Repairing air leaks can reduce compressed air system

energy use by 30% or more.19

Compressed Air Wise Rule 11

Repairing air leaks can reduce a facility’s total energy

use by about one-half percent, with an average simple

payback of 3 months.20

Compressed Air Wise Rule 12

It takes approximately 2.5 to 5.0 kWh to compress

1,000 ft3 of air to 100 psi.21,22 Each psi reduction in

compressed air loss from the distribution system (at

100 psi), reduces the compressor’s energy use by more

than one-half percent.23

Recover Waste Heat

Sixty to 90 percent of the energy of compression is available as

heat that can be recovered.25 Recovered waste heat may be used for

space heating or to supply heat to a manufacturing process. The

amount of heat energy that can be recovered depends on compressor characteristics and use factor. Waste heat recovery will be

most cost-effective when the compressor is located near the

process in which the heat is to be used.26 Air compressors 100 hp

and larger are often cooled with water from a cooling tower. The

temperature of the water leaving the compressor cooling coils may

be high enough that heat can be extracted and applied elsewhere.

Compressed Air Table 1

Energy Losses and Cost Impacts of Compressed

Air System Leaks24

Hole Leak Rate Energy Loss Cost of 

Diameter Wasted Energy

(inches) (cubic feet/min.) (kWh per year) (dollars per year)

1/64" 0.5 635 $20

1/32" 1.8 2,500 $90

1/16" 7.2 10,800 $350

1/8" 29.0 43,800 $1,500

1/4" 115.8 174,100 $5,900

3/8" 260.6 392,000 $13,200

Based on a 115 psi system with 8,520 hours of compressor operation. Electricity

price is assumed to be $0.034 per kWh.
6. Compressed Air Systems Wise Rules Page 25

For example, boiler feedwater could be preheated by the compressor cooling water.

Compressed Air Wise Rule 13

Air compressor waste heat recovery can reduce a facility’s total energy use by about 2% with an average

simple payback of 10 months.27

Filters and Coolers

Compressed air system efficiency suffers as compressed air system

filters and coolers become soiled. When filters are obstructed with

pipeline contaminants, significant pressure drops can develop,

requiring an increase in compressor discharge pressure. As a result

of the pressure increase, air leaks will become more costly.

28

Compressed Air Wise Rule 14

For every 1 psi increase in air compressor pressure gained

by periodic filter changes, air compressor energy use is

reduced by about one-half percent.29 Changing dryer filters at 8 or 10 psi drop per filter can eliminate this waste.

Compressed Air Wise Rule 15

For every 11°F decrease in air compressor working temperature, gained by careful maintenance of intercoolers,

air compressor energy use will decreased by 1%.30

Summary of Wise Rules for

Compressed Air Systems

Use the Wise Rules in Compressed Air Table 2 (next page) to identify and estimate potential energy saving from air compressor efficiency measures. When evaluating efficiency options, consider

potential costs, savings, payback and any secondary effects. While

some of the measures in Compressed Air Table 2 yield modest

potential savings as a percent of total facility energy use, the cost and

CO2 savings can be significant because most air compressors are driven by electricity. When using the Wise Rules, remember that several of the measures may overlap or complement each other and

energy savings rates may not be additive. In addition, Wise Rules for

similar measures are addressed from different perspectives. Some are

stated in terms of the air compressor’s energy use, others in terms of

a facility’s total energy use, or as a function of a physical parameter

(e.g., change in energy use with a change in pressure).

Compressed Air Notes

1 Talbott, E.M., Compressed Air Systems: A Guidebook on Energy and

Cost Savings, 2nd Edition, Fairmont Press, 1992, p. 160.

2 Oregon State University, AIRMaster Compressed Air System

Audit and Analysis Software, “How to Take a Self-Guided Tour of

Your Compressed Air System,” 1996 revised in 1997, p. 2. (SelfGuided Tour)

3 DOE/IAC Industrial Assessment Database, July 1997.

4 Rutgers University, Office of Industrial Productivity & Energy Assessment

(OIPEA), Modern Industrial Assessments: A Training Manual, Version 1.0b,

1995, p. 6-28.

5 Oregon State University, Self-Guided Tour, p. 5.

6 Rutgers, p. 6-28.

7 DOE/IAC Database.

8 Oregon State University, AIRMaster Compressed Air System Audit and

Analysis Software Version 1.4, “Analysis Methodology Manual for AIRMaster,”

1996 revised in 1997, p. 32.

9 Oregon State University, AIRMaster Compressed Air System Audit and

Analysis Software, “Case Studies: Compressed Air System Audits Using

AIRMaster,” 1996 revised in 1997 pp. 20-21.

10 Oregon State University, AIRMaster Case Studies, p. 12.

11 DOE/IAC Database.

12 Rutgers, p. 6-17.

13 Rutgers, p. 6-17.

14 DOE/IAC Database.

15 Oregon State University, Self-Guided Tour, p. 8.

16 DOE/IAC Database.

17 Talbott, E.M., p. 112.

18 Oregon State University, Self-Guided Tour, p. 8.

19 Oregon State University, Self-Guided Tour, p. 8.

20 DOE/IAC Database.

21 ICF Kaiser Consulting Group estimate based on Talbott, p. 77; 3M,

“Compressed Air Optimization,” 1994, p. 9.

22 Bonneville Power Administration, Industrial Compressed Air System Energy

Efficiency Guidebook, 1996, p. 2-2 and p. 4-5.

23 Talbott, p. 93.

24 Rutgers, p. 6-22.

25 Talbott, p. 91.

26 Rutgers, p. 6-16.

27 DOE/IAC Database.

28 Oregon State University, Self-Guided Tour, p. 9.

29 3M, “Compressed Air Optimization,” 1994, p. 9.

30 3M, p. 9.
Source references for each Wise Rule are included in the chapter notes.

* Percent of compressed air system energy use, unless noted.

** Based on compressed air system pressure of approximately 100 psi.

Page 26 Wise Rules 6. Compressed Air Systems

Compressed Air Table 2: Summary of Compressed Air Efficiency Measures

Source Measure Average Energy Savings* Average Annual Cost Savings

(IAC recommendation rate) (payback)

All Efficiency Improvements

Rule 1 Implement typical efficiency improvements, 20% to 50% 

which may include many or all of the 

measures below

Rule 2 Implement typical efficiency improvements, 0.4% of total facility energy use $4,300 (5 months)

which may include many or all of the 

measures below (68%)

Use Cooler Outside Air 

Rule 3 Use cooler air for intakes 1% per 5°F reduction less than 2 years

Rule 4 Use cooler air for intakes (37%) 0.2% of total facility energy use $1,400 (5 months)

Optimize Load 

Rule 5 Install or adjust unloading controls 10%

Rule 6 Upgrade screw compressor controls (1%) 0.8% of total facility energy use $7,900 (10 months)

Reduce Compressor Air Pressure

Rule 7 Reduce compressor pressure (15%) 0.4% of total facility energy use $2,800 (4 months)

Rule 8 Reduce compressor pressure 1% per 2 psi reduction**

Eliminate /Reduce Compressed Air Use

Rule 9 Eliminate/reduce some uses of air (5%) 0.6% of total facility energy use $7,300 (6 months)

Eliminate Air Leaks 

Rule 10 Repair air leaks 30% or more

Rule 11 Repair air leaks (36%) 0.4% of total facility energy use $3,900 (3 months)

Rule 12 Reduce air leaks in distribution system 0.7% decrease in compressor 

energy use per 1 psi loss 

reduction**

Table 1 Repair 1/16" leak 7,560 kWh per leak per yr $360/yr

Recover Waste Heat 

Rule 13 Recover waste heat from compressors (8%) 1.8% of total facility energy use $2,700 (10 months)

Change Filters and Clean Coolers

Rule 14 Change dryer filters at 8 to 10 psi drop 0.5% per avoided 1 psi drop in pressure

Rule 15 Clean intercoolers to reduce 1% per 11°F reduction

compressor working temperature
Energy Efficient Chillers and

Refrigeration Units

There are several energy efficiency options available when

installing new chilling equipment. For example, oversizing condenser water supply pipes can reduce head pressure and pumping

requirements. Evaporative cooled chillers consume considerably

less energy per ton of cooling capacity then water- and air-cooled

chillers. Using high efficiency compressors can also reduce chiller

energy use.

Process Cooling Wise Rule 1

Installing energy efficient chillers and refrigeration

systems can save about 1% of a facility’s total energy

use with an average simple payback of 23 months.1

7. Process Cooling Wise Rules Page 27

Energy Savings

Recommendation Rate

Chillers and Refrigeration

Process Cooling FIgure 1

Energy Savings from Process Cooling Efficiency Measures*

Recommendation Rate

Energy Savings Rate (percent of total facility energy use)

Process Cooling

(20 month payback)

Cooling Tower Measures

(14 month payback)

(23 month payback)

0%

0%

1% 2% 3% 4% 5% 6%

0.2% 0.4% 0.6% 0.8% 1.0% 1.2%

7. Process Cooling

Introduction

Many manufacturing processes require that materials or components be cooled to lower temperatures. Chillers, heat

pumps and other refrigeration equipment used as heat sinks for a

variety of industrial processes. Efficiency measures for process

cooling include using cooling tower water in place of refrigeration

or chilling, modifying the refrigeration system to operate at a lower

pressure, increasing chilled water temperatures, and using variable

speed drives (VSDs).

Process Cooling Figure 1 illustrates the potential energy savings

from process cooling efficiency measures based on specific recommendations in the DOE/IAC database. Process cooling measures

were recommended during six percent of the IAC audits with estimated savings of about one percent of a facility’s total energy use

and a simple payback of 20 months. Cooling tower measures were

recommended at three percent of audited facilities, with estimated

energy savings of almost one percent and a 14 month simple payback. Process Cooling Table 2, at the end of this chapter, summarizes the Wise Rules presented in this chapter, along with cost

savings estimates, where available.

* Results from the DOE/IAC Database (1/90-7/97). The IAC data reflect average potential impacts from energy efficiency measures at small-to-medium sized manufacturing

facilities across all sectors and regions of the country. Most IAC audit recommendations are expected to be implemented within two years and typically have a one-to-two year

payback period. (See Chapter 1.)
Cooling Tower Water

Using cooling tower water in place of a chiller can dramatically

reduce cooling energy use when the outside temperature is low

enough to achieve the required process temperature. This

method of cooling is referred as “free cooling” because the chiller

is not used. 

Process Cooling Wise Rule 2

“Free cooling” with cooling tower water can reduce a

facility’s total energy use by about 1% with an average

simple payback of 14 months.2

Process Cooling Wise Rule 3

Free cooling can reduce cooling system energy use by as

much as 40% depending on location and load profile.3

Refrigeration and Chillers

Reducing the cooling load is a direct approach to cutting chiller

energy use. A cooling system audit may identify opportunities for

improving insulation and eliminating unnecessary heat sources.

Raising the chilled water set temperature can also reduce chiller

energy use. By monitoring the minimum requirements on the

chilled water temperature, the chiller can be reset appropriately to

meet the demands of the system without wasting energy.

Refrigerant subcooling decreases the load on the compressor and

reduces chiller energy use. Oversizing or continuous operation of

cooling towers can lower condenser cooling water temperature and

reduce cooling system energy use. Careful system maintenance

and removal of non-condensable fluids can lower operating pressure and save energy.

Process Cooling Wise Rule 4

Increasing chilled water temperature by 1°F reduces

chiller energy use by 0.6% to 2.5%.4 (See Process

Cooling Table 1 for data on specific chiller types.)

Process Cooling Wise Rule 5

Reducing condenser pressure by 10 psi can decrease

refrigeration system energy use per ton of refrigeration

(kW/ton) by about 6%.6

Process Cooling Wise Rule 6

For each 1°F decrease in condenser cooling water

temperature, until optimal water temperature is

reached, there is a decrease in chiller energy use by up

to 3.5%.7

Freezing

The freezing process in a manufacturing facility can be made more

efficient by reducing heat loss through the use of improved insulation (such as air locks) and by freezing products in batches rather

than continuously.

Process Cooling Wise Rule 7

Eliminating heat losses from leaks and improper

defrosting can reduce refrigeration system energy use by

10% to 20%.8

Process Cooling Wise Rule 8

Freezing products in batches rather than continuously

can reduce freezing process energy use by up to 20%.9

Page 28 Wise Rules 7. Process Cooling

Procees Cooling Table 1 

Energy Savings from Increasing Chilled Water

Temperature

5

Chiller Type Energy Savings 

(Energy Savings per 1°F Increase in Temperature)

Screw Compressor 2.5%

Centrifugal Compressor 1.7%

Reciprocating Compressor 1.2%

Absorption Chiller 0.6%
Process Cooling Notes

1 DOE/IAC Industrial Assessment Database, July 1997.

2 DOE/IAC Database.

3 ICF Kaiser Consulting Group estimate based on D. Murphy, “Cooling

Towers Used for Free Cooling,” ASHRAE Journal, June 1991, pp. 16-26.

4 Clevenger, L. and J. Hassel, “Case Study: From Jump Start to High Gear –

How DuPont is Cutting Costs by Boosting Energy Efficiency,” Pollution

Prevention Review, Summer 1994, p. 304.

5 Clevenger and Hassel, p. 304.

6 Bonneville Power Administration (BPA), Washington State Energy Office,

Electric Ideas Clearinghouse, “Improving Industrial Refrigeration Energy

Efficiency,” October 1991, p. 3.

7 Bonneville Power Administration (BPA), Washington State Energy Office,

Electric Ideas Clearinghouse, “Optimizing Cooling Tower Performance,”

November 1991, p. 1.

8 Centre for the Analysis and Dissemination of Demonstrated Energy

Technologies (CADDET), Newsletter No. 4 December 1996, p. 16.

9 CADDET, p. 16.

10 York International, “HVAC&R Engineering Update: Examining Part-Load

Performance Gives You the Full Story on Chiller Efficiency,” 1994.

Variable Speed Drives 

The application of variable speed drives (VSD) can reduce energy

use when cooling loads vary over time. VSDs can be applied to the

compressor within the chiller or, in some situations, utilized in

chilled water distribution. 

Process Cooling Wise Rule 9

Installing variable speed drives in place of constant

speed systems can reduce cooling system energy use 

by 30% to 50%, depending on load profile.10

Summary of Wise Rules for

Process Cooling Systems

Process Cooling Table 2 (next page) summarizes Process Cooling

Wise Rules contained in this chapter. These Wise Rules can be

used to identify and estimate potential energy saving from boiler

efficiency measures. When evaluating options, consider potential

costs, savings, payback times, and any secondary impacts. When

using the Wise Rules, remember that several of the measures may

overlap or complement each other and energy savings rates may

not be additive. In addition, multiple Wise Rules may express savings for similar measures from different perspectives: in terms of a

facility’s total energy use, an end-use’s or process’ energy use, or as

a function of a physical parameter such as temperature. 

7. Process Cooling Wise Rules Page 29
Process Cooling Table 2: Summary of Process Cooling Efficiency Measures

Source Measure Average Energy Savings Average Annual Cost Savings

(IAC recommendation rate) and (Payback)

Implement typical efficiency improvements, 1.1% of total facility energy use $11,200 (20 months)

which may include many or all of 

the measures below (6%)

Rule 1 Install energy efficient chillers and 1.2% of total facility energy use $11,200 (23 months)

refrigeration units (3%)

Cooling Towers

Rule 2 Use cooling tower to replace 0.8% of total facility energy use $11,000 (14 months)

chiller for free cooling (3%)

Rule 3 Use free cooling up to 40% of cooling system energy

Refrigeration and Chillers

Rule 4 Increase chilled water temperature 0.6% to 2.5% reduction in energy 

input per 1°F increase

Rule 5 Reduce condenser pressure 6% decrease in refrigeration energy 

use per ton for each 10 psi reduction

Rule 6 Decrease condenser working temperature 3.5% reduction in chiller energy 

for each 1°F decrease

Freezing

Rule 7 Reduce heat loss and improper defrosting 10% to 20% decrease in freezer 

energy use

Rule 8 Use continuous freezing 20% decrease in freezer energy use

Rule 9 Install variable speed drives 30% to 50% reduction in cooling 

energy use

Page 30 Wise Rules 7. Process Cooling

Source references for each Wise Rule are included in the chapter notes.
Appendix A Wise Rules Page 31

Table A-1: SIC Code Definitions

SIC Code Classification

20 Food and Kindred Products

21 Tobacco*

22 Textile Mill Products

23 Apparel and Other Textile Products

24 Lumber and Wood Products

25 Furniture and Fixtures

26 Paper and Allied Products

27 Printing and Publishing

28 Chemicals and Allied Products

29 Petroleum and Coal Products

30 Rubber and Misc. Plastics Products

31 Leather and Leather Products

32 Stone, Clay and Glass Products 

33 Primary Metal Industries

34 Fabricated Metal Industries

35 Industrial Machinery and Equipment

36 Electronic and Other Electric Equipment

37 Transportation Equipment

38 Instruments and Related Products

39 Misc. Manufacturing Industries

*Only three IAC audits were conducted for SIC 21 (1/91-7/97).

Appendix A

Sector-Specific Energy Potential

I

n this appendix, we present examples of sector-specific savings

from the DOE IAC database. The IAC audit database contains

information on the expected impacts from energy efficiency

measures recommended at small-to-medium sized manufacturing facilities. IAC audits typically recommend measures with

short (one to two year) payback periods. The energy and cost

savings represent averages across industry groups, years, and

regions.

“Average percent energy savings” are defined as the average

reduction in a facility’s total energy use resulting from the implementation of a specific recommendation. For example, a typical

facility in the food industry (SIC 20) could expect to save about

six percent of their total facility energy use by implementing the

measures recommended during an IAC audit (refer to Table A-2).

The average simple payback period is defined as the amount of

time it takes to recover initial investment costs through energy

savings.

Table A-1 provides the definition of the Standard Industrial

Classification (SIC) codes for manufacturing industries.
Page 32 Wise Rules Appendix A

Table A-2: Average Impacts of All Energy Efficiency Measures Recommended by IAC Audits, by Sector*

SIC Code & Manufacturing Average Annual Average Annual Average Average Annual Average

Classification Energy Savings Energy Savings Implementation Cost Savings Simple 

(% of total facility (MMBtu) Cost (dollars) Payback

energy use) (dollars) (months)

20 Food and Kindred Products 6.2% 4,400 78,000 41,000 23 

21 Tobacco** 4.4% 8,800 85,000 52,000 19

22 Textile Mill Products 6.8% 8,300 103,000 64,000 19

23 Apparel and Other Textile Products 8.8% 1,700 22,000 21,000 13

24 Lumber and Wood Products 4.7% 7,600 86,000 56,000 19

25 Furniture and Fixtures 12.3% 3,700 47,000 29,000 20

26 Paper and Allied Products 8.5% 7,900 65,000 51,000 15

27 Printing and Publishing 7.1% 1,800 42,000 26,000 20

28 Chemicals and Allied Products 5.7% 6,200 66,000 37,000 21

29 Petroleum and Coal Products 13.4% 16,400 189,000 80,000 28

30 Rubber and Misc. Plastics Products 4.2% 2,500 43,000 35,000 15

31 Leather and Leather Products 4.0% 1,300 25,000 18,000 16

32 Stone, Clay and Glass Products 5.2% 16,800 183,000 98,000 22

33 Primary Metal Industries 7.0% 5,700 57,000 46,000 15

34 Fabricated Metal Industries 7.2% 2,900 33,000 27,000 14

35 Industrial Machinery and Equipment 5.9% 2,200 31,000 25,000 15

36 Electronic and Other Electric Equipment 8.5% 3,200 51,000 39,000 16

37 Transportation Equipment 7.3% 2,600 38,000 30,000 15

38 Instruments and Related Products 8.8% 2,300 41,000 32,000 15

39 Misc. Manufacturing Industries 9.7% 2,300 30,000 24,000 15

* Based on DOE/IAC estimates at audits of 4,300 manufacturing companies (1/90-7/97). Savings may not be additive.

** Only three IAC audits were conducted for Tobacco companies (SIC 21).
Appendix A Wise Rules Page 33

Table A-3: Food and Kindred Products Sector*(SIC 20)

Measure Recommendation Average Annual Average Annual Average Average Average

Rate Energy Savings Energy Savings Implementation Annual Cost Simple

(% of total facility (MMBtu) Cost Savings Payback

energy use) (dollars) (dollars) (months)

Miscellaneous Heat 

Recovery 1% 21.2% 18,500 144,300 54,800 32

Steam Operations 2% 8.2% 4,800 400 11,400 0

Cogeneration** 5% 5.5% 7,100 705,900 229,000 37

Boiler Hardware 3% 5.5% 2,000 15,200 7,600 24

Other Process Waste

7% 5.2% 3,700 19,600 13,600 17 Heat Recovery 

Heat Recovery

from Equipment 15% 4.5% 2,700 15,600 10,000 19

Chillers and 

Refrigeration 12% 3.2% 1,900 26,300 15,200 21

Flue Gas Recuperation 8% 2.9% 2,300 11,700 7,100 20

Boiler Maintenance 36% 2.3% 2,000 1,200 5,600 3

Steam Condensate 9% 2.3% 1,300 3,100 6,900 5

Thermal System 

Insulation 23% 2.2% 1,700 4,200 3,400 15

Steam Leaks and

Insulation 20% 0.9% 900 1,600 3,200 6

Motor Hardware 62% 0.6% 470 11,300 6,300 22

Air Compressor

Operations 35% 0.5% 300 1,400 3,600 5

Lighting Hardware 75% 0.4% 250 5,800 4,200 17

* Calculations based on IAC estimates at audits of 527 companies in SIC 20 (1/90 - 7/97). Savings may not be additive.

** Cogeneration energy savings are based on primary fuel savings from electricity generation, including fuel inputs at off-site powerplants for purchased electricity.
Page 34 Wise Rules Appendix A

Table A-4: Textile Mill Products*(SIC 22)

Measure Recommendation Average Annual Average Annual Average Average Average

Rate Energy Savings Energy Savings Implementation Annual Cost Simple

(% of total facility (MMBtu) Cost Savings Payback

energy use) (dollars) (dollars) (months)

Cogeneration** 3% 16.0% 9,700 211,000 111,000 23

Steam Operations 2% 7.7% 15,400 9,000 42,000 3

Heat Recovery from

10% 5.6% 4,700 11,000 15,000 9 Equipment 

Other Process Waste 

13% 4.1% 5,500 22,000 19,000 14 Heat Recovery

Boiler Hardware 5% 3.4% 6,000 60,000 21,000 34

Steam Condensate 10% 2.6% 4,200 16,000 14,000 13

Flue Gas Recuperation 13% 2.2% 4,900 19,000 14,000 16

Boiler Maintenance 27% 1.8% 2,500 15,000 13,000 14

Thermal System 26% 1.3% 1,200 4,000 5,000 10 Insulation

Steam Leaks and

22% 0.8% 1,300 1,000 4,000 4 Insulation 

Lighting Hardware 77% 0.7% 850 38,000 13,000 35

Motor Hardware 64% 0.5% 700 26,700 9,200 34

Air Compressor Operations 49% 0.5% 600 3,000 7,000 5

Air Compressor Hardware 36% 0.5% 500 2,000 5,000 5

Motor Operations 49% 0.4% 600 11,000 7,000 18

* Calculations based on IAC estimates at audits of 144 companies in SIC 22 (1/90 - 7/97). Savings may not be additive.

** Cogeneration energy savings are based on primary fuel savings from electricity generation, including fuel inputs at off-site powerplants for purchased electricity.
Appendix A Wise Rules Page 35

Table A-5: Apparel and Other Textile Products* (SIC 23)

Measure Recommendation Average Annual Average Annual Average Average Average

Rate Energy Savings Energy Savings Implementation Annual Cost Simple

(% of total facility (MMBtu) Cost Savings Payback

energy use) (dollars) (dollars) (months)

Miscellaneous Cooling 1% 46.2% 4,000 240,000 84,600 34

Space Conditioning 19% 8.3% 600 2,200 4,500 6 Controls

Flue Gas Recuperation 4% 6.7% 650 5,600 3,300 20

Building Envelope 4% 5.3% 450 1,200 2,500 6 Infiltration

Air Circulation Hardware 12% 4.9% 750 4,200 10,300 5

Space Conditioning 15% 4.3% 700 3,200 8,600 4 Operation

Other Process Waste 

5% 3.5% 350 1,700 2,100 9 Heat Recovery

Heat Recovery from 

19% 3.0% 350 2,000 1,400 17 Equipment

Lighting Operation 21% 2.9% 400 8,200 7,600 13

Thermal System 15% 2.7% 1,700 3,600 6,800 6 Insulation

Lighting Hardware 81% 1.7% 300 10,300 5,800 21

Steam Leaks and 16% 1.6% 600 950 1,700 7 Insulation

Boiler Maintenance 21% 1.2% 400 1,300 2,000 7

Motor Hardware 35% 0.7% 150 6,700 2,500 33

Air Compressor

51% 0.5% 100 350 1,600 2 Operations

* Calculations based on IAC estimates at audits of 113 companies in SIC 23 (1/90 - 7/97). Savings may not be additive.
Page 36 Wise Rules Appendix A

Table A-6: Lumber and Wood Products* (SIC 24)

Measure Recommendation Average Annual Average Annual Average Average Average

Rate Energy Savings Energy Savings Implementation Annual Cost Simple

(% of total facility (MMBtu) Cost Savings Payback

energy use) (dollars) (dollars) (months)

Air Circulation 

1% 11.0% 1,000 11,900 4,800 30 Hardware

Heating/Cooling 4% 8.0% 800 6,600 5,100 15 Hardware

Boiler Maintenance 14% 7.0% 13,100 2,900 18,100 2

Boiler Operation 3% 4.8% 27,700 9,700 19,800 6

Cogeneration** 6% 4.6% 41,700 680,000 297,000 27

Heat Recovery 10% 2.0% 700 8,100 2,700 36 from Equipment

Steam Leaks and 

11% 1.7% 4,800 3,000 5,800 6 Insulation 

Space Conditioning 7% 1.4% 350 1,000 2,600 5 Controls

Thermal System 9% 0.8% 1,900 4,600 3,300 17 Insulation

Air Compressor 

63% 0.3% 650 5,800 8,400 8 Operations

Motor Hardware 74% 0.2% 450 17,000 7,000 29

Motor Operations 55% 0.2% 250 7,100 3,700 23

* Calculations based on IAC estimates at audits of 213 companies in SIC 24 (1/90 - 7/97). Savings may not be additive.

** Cogeneration energy savings are based on primary fuel savings from electricity generation, including fuel inputs at off-site powerplants for purchased electricity.
Appendix A Wise Rules Page 37

Table A-7: Furniture and Fixtures* (SIC 25)

Measure Recommendation Average Annual Average Annual Average Average Average

Rate Energy Savings Energy Savings Implementation Annual Cost Simple

(% of total facility (MMBtu) Cost Savings Payback

energy use) (dollars) (dollars) (months)

Cogeneration** 5% 17.4% 17,400 402,900 117,000 41

Boiler Hardware 2% 14.1% 15,600 2,300 38,700 1

General Ventilation 8% 7.7% 3,000 19,800 10,800 22

Other Process 

5% 7.7% 3,400 11,700 12,500 11 Waste Heat Recovery

Heat Recovery 21% 6.4% 1,800 4,700 6,200 9 from Equipment

Thermal System 11% 5.8% 2,500 14,000 7,400 23 Insulation

Space Conditioning 16% 3.8% 700 4,100 5,000 10 Operation

Space Conditioning 11% 3.8% 500 2,100 3,100 8 Controls

Boiler Maintenance 9% 3.4% 800 1,000 1,500 9

Building Envelope 15% 2.9% 750 5,400 2,800 23 Infiltration

Air Circulation

10% 2.8% 550 6,500 3,500 22 Hardware

Equipment Use 18% 2.1% 500 450 4,400 1 Reduction 

Lighting Hardware 77% 1.0% 200 7,500 4,500 20

Air Compressor 

60% 0.7% 250 950 3,400 3 Operations

Motor Hardware 50% 0.5% 150 7,000 3,800 22

* Calculations based on IAC estimates at audits of 109 companies in SIC 25 (1/90 - 7/97). Savings may not be additive.

** Cogeneration energy savings are based on primary fuel savings from electricity generation, including fuel inputs at off-site powerplants for purchased electricity.
Page 38 Wise Rules Appendix A

Table A-8: Paper and Allied Products* (SIC 26)

Measure Recommendation Average Annual Average Annual Average Average Average

Rate Energy Savings Energy Savings Implementation Annual Cost Simple

(% of total facility (MMBtu) Cost Savings Payback

energy use) (dollars) (dollars) (months)

Mechanical System 1% 43.1% 62,500 219,400 161,000 16 Design

Flue Gas-Other Uses 2% 19.2% 33,700 69,800 98,200 9

Cogeneration** 4% 11.0% 29,500 400,100 275,900 17

Other Process Waste

6% 7.5% 15,900 72,700 39,200 22 Heat Recovery

Steam Trap Management 3% 7.0% 4,400 2,300 21,000 1

Heating/Cooling 4% 4.7% 1,200 35,200 9,900 43 Hardware

Miscellaneous Building 4% 4.6% 2,400 19,700 6,500 36 Envelope

Boiler Operation 7% 2.9% 2,300 3,000 8,200 4

Building Envelope 12% 2.5% 1,100 13,900 4,300 39 Infiltration

Heat Recovery 15% 1.9% 2,500 10,300 7,600 16 from Equipment

Space Conditioning 10% 1.9% 850 2,500 4,300 7 Controls

Boiler Maintenance 25% 1.2% 1,900 4,200 6,100 8

Lighting Hardware 78% 0.5% 350 9,700 6,900 17

Air Compressor 

39% 0.5% 300 1,100 4,600 3 Operations

Motor Hardware 61% 0.4% 450 14,600 8,200 21

* Calculations based on IAC estimates at audits of 226 companies in SIC 26 (1/90 - 7/97). Savings may not be additive.

** Cogeneration energy savings are based on primary fuel savings from electricity generation, including fuel inputs at off-site powerplants for purchased electricity.
Appendix A Wise Rules Page 39

Table A-9: Printing and Publishing* (SIC 27)

Measure Recommendation Average Annual Average Annual Average Average Average

Rate Energy Savings Energy Savings Implementation Annual Cost Simple

(% of total facility (MMBtu) Cost Savings Payback

energy use) (dollars) (dollars) (months)

Heating/Cooling Hardware 7% 5.6% 450 26,700 9,600 33

Flue Gas Recuperation 3% 4.2% 2,000 15,600 8,300 23

Space Conditioning 19% 4.0% 850 4,100 4,500 11 Controls

Heat Recovery from 

16% 3.5% 1,000 5,600 5,200 13 Equipment

Boiler Hardware 4% 3.2% 800 12,200 4,300 34

Air Circulation 

7% 2.9% 400 4,900 2,300 25 Hardware

Miscellaneous Building 10% 2.4% 800 16,000 5,000 37 Envelope

Space Conditioning 25% 2.2% 300 3,000 2,900 13 Operation

Equipment Use 12% 1.7% 600 46,100 4,700 118 Reduction

Motor Hardware 42% 1.3% 300 6,900 5,400 15

Lighting Hardware 79% 1.0% 300 9,200 5,400 20

Building Envelope 15% 1.0% 250 1,100 1,300 11 Infiltration

Air Compressor 45% 0.8% 250 1,000 4,000 3 Operations

Motor Operations 31% 0.5% 150 2,700 2,300 14

Lighting Controls 31% 0.4% 120 1,200 1,700 9

* Calculations based on IAC estimates at audits of 182 companies in SIC 27 (1/90 - 7/97). Savings may not be additive.
Page 40 Wise Rules Appendix A

Table A-10: Chemicals and Allied Products* (SIC 28)

Measure Recommendation Average Annual Average Annual Average Average Average

Rate Energy Savings Energy Savings Implementation Annual Cost Simple

(% of total facility (MMBtu) Cost Savings Payback

energy use) (dollars) (dollars) (months)

Cogeneration** 4% 18.6% 11,400 772,000 147,900 63

General Ventilation 1% 9.9% 900 1,500 3,700 5

Boiler Hardware 1% 9.9% 20,500 125,000 73,900 20

Flue Gas Recuperation 9% 5.1% 8,000 27,900 22,200 15

Heating/Cooling 5% 3.9% 1,900 56,300 19,600 34 Hardware

Other Process Waste 

7% 2.7% 7,400 13,000 21,000 8 Heat Recovery

Boiler Maintenance 23% 2.2% 2,500 1,200 6,800 2

Space Conditioning 9% 2.2% 800 2,400 8,400 3 Operation

Heat Recovery from 

10% 1.9% 1,200 4,400 4,800 11 Equipment

Steam Leaks and 

17% 1.6% 4,600 2,300 8,800 3 Insulation

Equipment Use 12% 1.5% 950 1,500 4,400 4 Reduction

Air Compressor 

37% 0.8% 400 450 5,400 1 Operations

Motor Hardware 62% 0.5% 450 15,000 6,000 30

Lighting Hardware 75% 0.3% 200 7,200 4,200 21

Motor Operations 34% 0.3% 500 1,700 2,700 8

* Calculations based on IAC estimates at audits of 191 companies in SIC 28 (1/90 - 7/97). Savings may not be additive.

** Cogeneration energy savings are based on primary fuel savings from electricity generation, including fuel inputs at off-site powerplants for purchased electricity.
Appendix A Wise Rules Page 41

Table A-11: Petroleum and Coal Products* (SIC 29)

Measure Recommendation Average Annual Average Annual Average Average Average

Rate Energy Savings Energy Savings Implementation Annual Cost Simple

(% of total facility (MMBtu) Cost Savings Payback

energy use) (dollars) (dollars) (months)

Cogeneration** 3% 23.6% 262,200 4,815,000 1,247,700 46

Furnace Operations 3% 19.6% 9,500 4,000 23,700 2

Other Equipment 3% 10.1% 16,000 47,900 46,000 13 Hardware

Furnace Hardware 3% 8.8% 950 0 3,800 0

Space Conditioning 3% 8.1% 2,000 400 7,000 1 Controls

Flue Gas Recuperation 15% 7.8% 9,200 40,900 36,100 14

Boiler Hardware 6% 7.4% 2,300 11,000 6,400 21

Flue Gas-Other Uses 6% 5.3% 8,700 12,000 30,900 5

Heat Recovery from 

6% 3.8% 15,300 117,900 44,400 32 Equipment

Thermal System 65% 3.7% 3,900 8,100 18,400 5 Insulation

Steam Trap 6% 3.6% 3,300 4,700 9,500 6 Management 

Boiler Operation 12% 3.0% 2,300 6,700 7,500 11

Boiler Maintenance 21% 2.5% 2,900 3,300 9,500 4

Furnace Maintenance 12% 1.7% 600 750 1,600 6

Steam Leaks and 

32% 0.9% 1,200 1,400 6,200 3 Insulation

* Calculations based on IAC estimates at audits of 34 companies in SIC 29 (1/90 - 7/97). Savings may not be additive.

** Cogeneration energy savings are based on primary fuel savings from electricity generation, including fuel inputs at off-site powerplants for purchased electricity.
Page 42 Wise Rules Appendix A

Table A-12: Rubber and Misc. Plastics Products* (SIC 30)

Measure Recommendation Average Annual Average Annual Average Average Average

Rate Energy Savings Energy Savings Implementation Annual Cost Simple

(% of total facility (MMBtu) Cost Savings Payback

energy use) (dollars) (dollars) (months)

Flue Gas Recuperation 4% 8.3% 8,000 19,800 20,600 12

Other Process Waste

3% 5.0% 2,300 24,200 11.600 25 Heat Recovery

Other Equipment 7% 2.4% 650 20,100 11,300 21 Hardware

Heating/Cooling 7% 2.3% 800 20,300 9,200 26 Hardware

Boiler Maintenance 11% 2.2% 1,700 3,000 6,300 6

Heat Recovery 10% 2.2% 1,100 5,100 4,900 12 from Equipment

Equipment Use 13% 2.1% 650 2,600 8,200 4 Reduction

Space Conditioning 10% 2.0% 800 3,100 5,800 6 Operation

Equipment Automation 13% 1.7% 450 2,800 7,400 5

Air Circulation Hardware 10% 1.7% 650 6,900 4,300 19

Space Conditioning 12% 1.6% 500 1,300 3,700 4 Controls

Thermal System 33% 0.8% 500 3,000 6,300 6 Insulation

Lighting Hardware 74% 0.5% 300 7,200 5,100 17

Motor Hardware 59% 0.5% 400 15,200 6,800 27

Air Compressor 42% 0.4% 250 1,300 4,500 3 Operations

* Calculations based on IAC estimates at audits of 440 companies in SIC 30 (1/90 - 7/97). Savings may not be additive.
Appendix A Wise Rules Page 43

Table A-13: Leather and Leather Products* (SIC 31)

Measure Recommendation Average Annual Average Annual Average Average Average

Rate Energy Savings Energy Savings Implementation Annual Cost Simple

(% of total facility (MMBtu) Cost Savings Payback

energy use) (dollars) (dollars) (months)

Thermal System 6% 7.3% 750 2,100 4,800 5 Infiltration

Steam Maintenance 3% 5.9% 700 200 2,400 1

Steam Trap Management 6% 5.7% 1,400 1,700 4,500 5

Heating/Cooling 9% 5.3% 100 19,100 3,000 77 Hardware

Space Conditioning 15% 3.8% 500 5,300 2,500 25 Operation

Lighting Level 12% 2.3% 250 700 3,400 2

Steam Leaks and 

21% 1.8% 1,200 1,600 4,100 5 Insulation

Boiler Maintenance 21% 1.8% 1,100 2,500 3,400 9

Heat Recovery from 

21% 1.4% 100 450 900 6 Equipment

Lighting Hardware 61% 0.9% 300 18,100 7,700 28

Lighting Controls 18% 0.7% 200 1,000 1,700 7

Thermal System 27% 0.6% 300 2,500 1,600 19 Insulation

Air Compressor 

52% 0.5% 200 850 4,300 2 Operations

Air Compressor 

58% 0.3% 70 600 1,400 5 Hardware

Motor Hardware 39% 0.3% 200 7,700 5,000 18

* Calculations based on IAC estimates at audits of 33 companies in SIC 31 (1/90 - 7/97). Savings may not be additive.
Page 44 Wise Rules Appendix A

Table A-14: Stone, Clay and Glass Products* (SIC 32)

Measure Recommendation Average Annual Average Annual Average Average Average

Rate Energy Savings Energy Savings Implementation Annual Cost Simple

(% of total facility (MMBtu) Cost Savings Payback

energy use) (dollars) (dollars) (months)

Miscellaneous Heat

1% 38.8% 7,400 32,300 36,900 11 Recovery

Thermal System 1% 23.7% 600 6,000 3,800 19 Isolation

Cogeneration** 7% 10.2% 123,800 1,447,400 464,000 37

General Operations 1% 5.3% 1,000 6,000 4,600 15 Maintenance

Flue Gas-Other Uses 6% 4.2% 27,700 46,100 65,800 8

Flue Gas Recuperation 9% 4.1% 14,800 54,300 33,400 19

Thermal System 22% 2.4% 5,000 7,200 15,500 6 Insulation

Heat Recovery 12% 2.3% 3,600 5,100 10,200 6 from Equipment

Boiler Maintenance 11% 2.2% 2,300 1,000 8,900 1

Other Equipment 9% 2.2% 5,000 153,800 89,700 21 Hardware

Other Process Waste 

6% 2.2% 6,300 23,500 19,000 15 Heat Recovery

Building Envelope 8% 1.4% 4,700 1,800 10,600 2 Infiltration

Boiler Operation 4% 1.4% 2,600 3,400 7,600 5

Motor Hardware 70% 0.3% 1,100 30,800 15,000 25

Air Compr essor 56% 0.3% 850 3,200 9,800 4 Operations

* Calculations based on IAC estimates at audits of 151 companies in SIC 32 (1/90 - 7/97). Savings may not be additive.

** Cogeneration energy savings are based on primary fuel savings from electricity generation, including fuel inputs at off-site powerplants for purchased electricity.
Appendix A Wise Rules Page 45

Table A-15: Primary Metal Industries* (SIC 33)

Measure Recommendation Average Annual Average Annual Average Average Average

Rate Energy Savings Energy Savings Implementation Annual Cost Simple

(% of total facility (MMBtu) Cost Savings Payback

energy use) (dollars) (dollars) (months)

Cogeneration** 2% 12.1% 8,100 473,600 112,000 51

Boiler Operation 4% 7.0% 6,300 13,000 18,100 9

Furnace Operations 3% 6.9% 11,500 2,900 26,400 1

Space Conditioning 4% 6.8% 3,300 18,700 8,900 25 Operation

Flue Gas-Other Uses 8% 6.2% 10,700 106,400 52,400 24

Furnace Maintenance 3% 6.2% 4,100 7,200 15,700 6

Flue Gas Recuperation 14% 5.9% 6,000 20,600 17,800 14

Building Envelope 6% 3.7% 1,600 10,600 6,200 21 Infiltration

Heat Recovery from 

12% 2.8% 1,600 8,500 6,800 15 Equipment

Boiler Maintenance 10% 2.0% 1,400 1,600 5,500 3

Thermal System 24% 1.7% 1,400 2,500 6,400 5 Insulation

Equipment Use 11% 1.7% 2,000 1,100 7,600 2 Reduction

Motor Hardware 62% 0.6% 500 11,000 7,000 20 

Air Compressor 45% 0.6% 450 2,300 6,600 4 Operations

Lighting Hardware 70% 0.3% 250 6,000 3,800 19

* Calculations based on IAC estimates at audits of 263 companies in SIC 33 (1/90 - 7/97). Savings may not be additive.

** Cogeneration energy savings are based on primary fuel savings from electricity generation, including fuel inputs at off-site powerplants for purchased electricity.
Page 46 Wise Rules Appendix A

Table A-16: Fabricated Metal Industries* (SIC 34)

Measure Recommendation Average Annual Average Annual Average Average Average

Rate Energy Savings Energy Savings Implementation Annual Cost Simple

(% of total facility (MMBtu) Cost Savings Payback

energy use) (dollars) (dollars) (months)

Cogeneration** 2% 15.2% 13,000 323,000 121,000 32

Flue Gas-Other Uses 4% 8.2% 6,800 19,300 21,400 11

Heating/Cooling 7% 4.5% 950 20,100 5,300 46 Hardware

Flue Gas Recuperation 5% 4.1% 4,200 20,700 11,000 23

Air Circulation 

8% 2.6% 800 5,400 4,500 14 Hardware

Miscellaneous Building 7% 2.6% 1,100 17,100 5,400 38 Envelope

Heat Recovery from 

16% 2.5% 900 3,700 3,800 12 Equipment

Boiler Maintenance 12% 2.5% 1,500 1,400 4,600 4

Space Conditioning 9% 2.1% 700 1,500 3,800 5 Operation

Building Envelope 15% 2.0% 700 2,800 3,000 11 Infiltration

Thermal System 21% 1.8% 800 3,800 3,800 12 Insulation

Space Conditioning 14% 1.5% 600 1,500 3,500 5 Controls

Air Compressor 

55% 0.6% 250 890 4,300 2 Operations

Lighting Hardware 75% 0.5% 200 6,700 4,800 17

Motor Hardware 54% 0.5% 200 6,600 3,900 20

* Calculations based on IAC estimates at audits of 570 companies in SIC 34 (1/90 - 7/97). Savings may not be additive.

** Cogeneration energy savings are based on primary fuel savings from electricity generation, including fuel inputs at off-site powerplants for purchased electricity.
Appendix A Wise Rules Page 47

Table A-17: Industrial Machinery and Equipment* (SIC 35)

Measure Recommendation Average Annual Average Annual Average Average Average

Rate Energy Savings Energy Savings Implementation Annual Cost Simple

(% of total facility (MMBtu) Cost Savings Payback

energy use) (dollars) (dollars) (months)

Building Envelope 15% 4.3% 1,000 3,200 3,300 12 Infiltration

General Ventilation 7% 4.1% 900 2,800 4,300 8

Air Circulation Hardware 9% 4.0% 750 6,600 4,200 19

Space Conditioning 15% 3.8% 900 3,100 6,000 6 Operation

Heating/Cooling 8% 3.8% 700 35,000 12,600 33 Hardware

Space Conditioning 13% 3.6% 750 1,700 3,800 5 Controls

Miscellaneous Building 6% 3.2% 1,000 22,500 4,900 55 Envelope

Other Equipment 7% 3.0% 400 6,500 5,600 14 Hardware

Equipment Use 15% 2.8% 750 900 4,200 3 Reduction

Heat Recovery from 

21% 1.8% 600 3,200 2,800 14 Equipment

Boiler Maintenance 10% 1.7% 600 1,000 2,300 5

Lighting Level 12% 1.4% 400 1,200 5,700 2

Lighting Hardware 82% 0.7% 250 9,800 5,000 23

Air Compressor 

55% 0.6% 250 1,000 3,700 3 Operations

Motor Hardware 47% 0.6% 150 5,900 2,800 25

* Calculations based on IAC estimates at audits of 438 companies in SIC 35 (1/90 - 7/97). Savings may not be additive.
Page 48 Wise Rules Appendix A

Table A-18: Electronic and Other Electric Equipment* (SIC 36)

Measure Recommendation Average Annual Average Annual Average Average Average

Rate Energy Savings Energy Savings Implementation Annual Cost Simple

(% of total facility (MMBtu) Cost Savings Payback

energy use) (dollars) (dollars) (months)

Humidity Control 1% 31.2% 16,000 143,400 97,000 18

Cogeneration** 1% 22.1% 47,000 286,800 303,600 11

Heating/Cooling 8% 6.2% 2,000 40,200 20,500 24 Hardware

Heat Recovery from 

20% 3.5% 1,000 6,400 5,400 14 Equipment

Space Conditioning 17% 3.4% 1,000 4,000 8,400 6 Controls

Other Process Waste 

5% 3.1% 2,300 17,400 11,900 18 Heat Recovery

Space Conditioning 14% 2.9% 850 8,300 7,800 13 Operation

Air Circulation 

8% 2.8% 650 6,200 7,400 10 Hardware

Other Equipment 7% 2.6% 600 19,200 7,700 30 Hardware

Miscellaneous Building 6% 2.6% 550 15,300 5,100 36 Envelope

Building Envelope 9% 2.4% 600 2,500 5,300 6 Infiltration

Thermal System 20% 1.2% 500 2,400 4,600 6 Insulation

Lighting Hardware 77% 1.1% 400 15,100 8,000 23

Motor Hardware 55% 0.7% 250 9,100 5,000 22

Air Compressor 43% 0.6% 200 1,300 3,600 4 Operations

* Calculations based on IAC estimates at audits of 287 companies in SIC 36 (1/90 - 7/97). Savings may not be additive.

** Cogeneration energy savings are based on primary fuel savings from electricity generation, including fuel inputs at off-site powerplants for purchased electricity.
Appendix A Wise Rules Page 49

Table A-19: Transportation Equipment* (SIC 37)

Measure Recommendation Average Annual Average Annual Average Average Average

Rate Energy Savings Energy Savings Implementation Annual Cost Simple

(% of total facility (MMBtu) Cost Savings Payback

energy use) (dollars) (dollars) (months)

Flue Gas Recuperation 3% 8.4% 7,000 20,000 19,800 12

Miscellaneous Building 5% 7.0% 1,000 9,700 4,600 25 Envelope

Heating/Cooling 11% 5.8% 1,000 17,000 12,400 17 Hardware

Space Conditioning 12% 3.7% 1,000 3,000 6,200 6 Operation

Space Conditioning 18% 2.8% 1,000 2,600 6,100 5 Controls

Building Envelope 9% 2.8% 850 2,600 4,200 7 Infiltration

Heat Recovery from 

21% 2.7% 1,000 7,100 4,000 22 Equipment

Boiler Maintenance 9% 2.4% 2,000 1,200 5,100 3

Equipment Automation 14% 1.8% 400 2,000 3,200 7

Lighting Level 15% 1.2% 350 3,300 6,200 6

Air Compressor 64% 1.0% 300 1,000 4,700 3 Operations

Lighting Hardware 79% 0.9% 300 11,200 5,400 25

Motor Hardware 56% 0.8% 300 8,400 4,300 23

Motor Operations 31% 0.6% 250 2,800 3,100 11

Air Compressor 

39% 0.4% 150 1,200 2,200 7 Hardware

* Calculations based on IAC estimates at audits of 214 companies in SIC 37 (1/90 - 7/97). Savings may not be additive.
Page 50 Wise Rules Appendix A

Table A-20: Instruments and Related Products* (SIC 38)

Measure Recommendation Average Annual Average Annual Average Average Average

Rate Energy Savings Energy Savings Implementation Annual Cost Simple

(% of total facility (MMBtu) Cost Savings Payback

energy use) (dollars) (dollars) (months)

Solar Loading 2% 10.3% 550 4,900 4,100 14

Other Equipment 5% 9.3% 1,000 60,600 26,600 27 Hardware 

Other Process Waste 

5% 6.7% 4,000 13,400 19,000 8 Heat Recovery

Space Conditioning 14% 5.3% 600 3,100 7,800 5 Operation

Heat Recovery from 

13% 4.7% 1,000 5,200 5,600 11 Equipment

General Ventilation 4% 4.6% 900 8,000 4,700 20

Equipment Use 14% 3.7% 700 600 4,400 2 Reduction

Heating/Cooling 7% 2.6% 450 40,400 12,400 39 Hardware

Lighting Hardware 83% 2.2% 450 18,900 10,300 22

Equipment Automation 19% 2.1% 400 2,900 3,900 9

Building Envelope 13% 1.7% 450 1,500 5,100 3 Infiltration

Thermal System 20% 1.1% 350 1,700 2,400 5 Insulation

Motor Hardware 57% 0.9% 250 9,400 4,400 25

Air Compressor 40% 0.7% 100 350 2,100 2 Operations

Lighting Controls 34% 0.6% 150 1,700 2,400 8

* Calculations based on IAC estimates at audits of 95 companies in SIC 38 (1/90 - 7/97). Savings may not be additive.
Appendix A Wise Rules Page 51

Table A-21: Misc. Manufacturing Industries* (SIC 39)

Measure Recommendation Average Annual Average Annual Average Average Average

Rate Energy Savings Energy Savings Implementation Annual Cost Simple

(% of total facility (MMBtu) Cost Savings Payback

energy use) (dollars) (dollars) (months)

Alternate Fossil

1% 25.5% 2,000 21,700 29,000 9 Fuel Switching

Boiler Operation 3% 24.0% 7,000 15,100 5,900 31

Cogeneration** 1% 15.9% 8,000 165,000 54,000 37

Heating/Cooling 5% 10.3% 1,000 58,400 14,100 50 Hardware

Solar Loading 4% 10.3% 700 13,900 4,400 38

Heat Recovery from 

12% 7.0% 2,000 4,800 11,500 5 Equipment

Flue Gas Recuperation 5% 6.2% 4,000 8,200 12,300 8

Boiler Maintenance 19% 5.6% 1,000 1,200 4,400 3

Miscellaneous Building 8% 4.6% 800 19,000 6,000 38 Envelope

Space Conditioning 13% 3.9% 600 1,700 3,000 7 Operation

Space Conditioning 13% 2.7% 1,000 2,800 7,800 4 Controls

Lighting Hardware 88% 1.0% 250 8,000 4,600 21

Air Compressor 48% 0.9% 150 950 3,100 4 Operations

Motor Hardware 45% 0.7% 100 4,300 2,200 24

Air Compressor 41% 0.5% 100 800 1,100 9 Hardware

* Calculations based on IAC estimates at audits of 75 companies in SIC 39 (1/90 - 7/97). Savings may not be additive.

** Cogeneration energy savings are based on primary fuel savings from electricity generation, including fuel inputs at off-site powerplants for purchased electricity.
Appendix B Wise Rules Page 52

Table B-1: Helpful Conversion Factors

To Convert To Multiply By

Tons Pounds 2000

Tons Metric Tons 0.9072

MMBtu Btu 106

kWh Wh 103

MWh kWh 103

kWh Btu 3413

Quads Btu 1015

(quadrillion Btu)

Quads kWh 2.93 x 1011

(quadrillion Btu)

Therms Btu 105

Horsepower (hp) kW 0.746

Btu Joule (J) 1055

kWh Joule (J) 3600

Carbon Carbon Dioxide 3.667

(mass units) (mass units) 

Carbon Dioxide Carbon 0.2727

(mass units) (mass units)

Carbon Carbon Dioxide 4.042

(metric tons) (tons)

Carbon Dioxide Carbon 1.237 x 10 -4

(pounds) (metric tons)

Appendix B 

Conversion Factors and Emission Coefficients

This appendix provides the necessary information to calculate

CO2 emissions reductions from energy efficiency measures.

Once you have qualified project impacts (using Wise Rules,

metered data, and/or engineering estimates), simply multiply the

energy savings by the appropriate CO2 emission coefficient. Use

Table B-2 to calculate CO2 emission reductions from fuel savings and use Table B-3 to calculate CO2 emissions reductions

from electricity savings. CO2 emissions from electricity generation are a function of powerplant efficiency and fuel use. The

CO2 emission coefficients in Table B-3 are average values that

reflect the mix of powerplants in each state. Feel free to use your

own site-specific information on fuel carbon content or purchased electricity CO2 emissions in place of the averages presented here.

Example 1: Boiler Fuel Savings

Consider a boiler tune-up that is estimated to save 1,000

MMBtu of natural gas per year. Multiply the 1,000 MMBtu

savings by the CO2 emission coefficient for natural gas, 117.08

pounds CO2 per MMBtu (Table B-2) to calculate annual savings

of 117,080 pounds of CO2. To express the greenhouse gas emissions reduction in metric tons of carbon, multiply the pounds

of CO2 saved by 1.237 x 10-4 (Table B-1) to yield 14.5 metric

tons of carbon.

Example 2: Air Compressor Electricity Savings

Consider a manufacturing facility in Florida that implements

compressed air system efficiency improvements that result in

annual savings of 100 MWh. Multiply the 100 MWh savings by

the CO2 emission factor for electricity generated in Florida,

0.587 metric tons CO2 per MWh (Table B-3), to calculate annual savings of 58.7 metric tons of CO2. To express the greenhouse

gas emissions reduction in metric tons of carbon, multiply the

metric tons of CO2 saved by 0.2727 (Table B-1) to yield 16.0

metric tons of carbon.
Page 53 Wise Rules Appendix B

Table B-2: Emission Coefficients by Fuel Type

Fuel Emission Coefficients

Pounds CO2 per Unit Volume or Mass Pounds CO2 per Million Btu 

Petroleum Products

Aviation Gasoline 18.355 per gallon 152.717

770.916 per barrel

Distillate Fuel (No. 1, No. 2, No. 4 Fuel Oil and Diesel) 22.384 per gallon 161.386

940.109 per barrel

Jet Fuel 21.439 per gallon 159.690

900.420 per barrel

Kerosene 21.537 per gallon 159.535

904.565 per barrel

Liquefied Petroleum Gases (LPG) 12.200 per gallon 138.846

512.415 per barrel

Motor Gasoline 19.641 per gallon 157.041

824.939 per barrel

Residual Fuel (No. 6 Fuel Oil) 26.033 per gallon 173.906

1,093.384 per barrel

Natural Gas and Other Gaseous Fuels

Methane 116.376 per 1000 ft3 115.258

Flare Gas 133.759 per 1000 ft3 120.721

Natural Gas (Pipeline) 120.593 per 1000 ft3 117.080

Propane 12.669 per gallon 139.178

532.085 per barrel

Electricity Varies depending on fuel used to generate electricity*

Coal

Anthracite 3852.156 per ton 227.400

Bituminous 4921.862 per ton 205.300

Subbituminous 3723.952 per ton 212.700

Lignite 2733.857 per ton 215.400

Renewable Sources

Geothermal Energy 0 0

Wind 0 0

Photovoltaic and Solar Thermal 0 0

Hydropower 0 0

Wood and Wood Waste** 3814 per ton 221.943

Municipal Solid Waste** 1999 per ton 199.854

Nuclear 0 0

Source: DOE/EIA, Form EIA-1605 Voluntary Reporting of Greenhouse Gases, Instructions, 1997, Appendix B. 

*For average electric power emission coefficients by state, see Table B-3.

**Fuel cycle emissions are likely to be less than the direct emissions because all or part of the fuel is renewable. These biofuels contain carbon that is part of the natural carbon

balance and that will not add to atmospheric concentrations of carbon dioxide.
Appendix B Wise Rules Page 54

State CO2 Emission Factors

lbs/kWh short tons/MWh metric tons/MWh

Alabama 1.369 0.684 0.621

Kentucky 1.930 0.965 0.869

Mississippi 1.075 0.537 0.487

Tennessee 1.335 0.668 0.606

West-South Central Region

Arkansas 1.286 0.643 0.584

Louisiana 1.388 0.694 0.629

Oklahoma 1.672 0.836 0.758

Texas 1.552 0.776 0.704

Mountain Region

Arizona 0.798 0.399 0.362

Colorado 2.001 1.000 0.908

Idaho 0.269 0.134 0.122

Montana 1.553 0.777 0.704

Nevada 1.875 0.937 0.850

New Mexico 1.405 0.703 0.637

Utah 1.990 0.995 0.903

Wyoming 2.194 1.097 0.995

Pacific Region Contiguous

California 0.756 0.378 0.343

Oregon 0.235 0.118 0.107

Washington 0.306 0.153 0.139

Pacific Region Non-Contiguous

Alaska 0.031 0.016 0.014

Hawaii

State CO2 Emission Factors

lbs/kWh short tons/MWh metric tons/MWh

New England Region

Connecticut 0.715 0.358 0.324

Maine 0.966 0.483 0.438

Massachusetts 1.459 0.729 0.662

New Hampshire 0.852 0.426 0.386

Rhode Island 1.091 0.546 0.495

Vermont 0.159 0.080 0.072

Mid Atlantic Region

New Jersey 0.774 0.387 0.351

New York 1.036 0.518 0.470

Pennsylvania 1.286 0.643 0.583

East-North Central Region

Illinois 0.866 0.433 0.393

Indiana 2.171 1.086 0.985

Michigan 1.576 0.788 0.715

Ohio 1.807 0.904 0.820

Wisconsin 1.343 0.671 0.609

West-North Central Region

Iowa 1.686 0.843 0.765

Kansas 1.703 0.852 0.773

Minnesota 1.627 0.814 0.738

Missouri 1.783 0.891 0.809

Nebraska 1.288 0.644 0.580

North Dakota 2.303 1.151 1.045

South Dakota 0.912 0.456 0.410

South Atlantic Region

Delaware 1.855 0.928 0.842

District of Columbia 2.649 1.324 1.192

Florida 1.294 0.647 0.587

Georgia 1.220 0.610 0.553

Maryland 1.356 0.678 0.615

North Carolina 1.350 0.675 0.612

South Carolina 0.688 0.344 0.312

Virginia 1.107 0.554 0.502

West Virginia 2.005 1.003 0.909

Table B-3: Electricity CO2 Emission Factors by State

East-South Central Region

U.S. Average

Source: DOE/EIA, Form EIA-1605 Voluntary Reporting of Greenhouse Gases,

Instructions, 1997, Appendix C.

1.291 0.646 0.586
Boiler Wise Rule 7

Using a characterizable fuel valve to match the air/fuel

ratios across the load range can save 2% to 12% of a

boiler’s fuel use at relatively low cost.

Boiler Wise Rule 8

Converting to air or steam atomizing burners from

conventional burners can reduce boiler fuel use by 

2% to 8%.

Boiler Wise Rule 9

Every 40°F reduction in net stack temperature (outlet

temperature minus inlet combustion air temperature) 

is estimated to save 1% to 2% of a boiler’s fuel use.

Boiler Wise Rule 10

Stack dampers prevent heat from being pulled up the

stack and can save 5% to 20% of a boiler’s fuel use.

Boiler Wise Rule 11

Direct contact condensation heat recovery can save

8% to 20% of a boiler’s fuel use, but costs may be relatively high.

Boiler Wise Rule 12

Preheating combustion inlet air can save about 3% of

a facility’s total energy use with an average simple payback of 8 months. 

Boiler Wise Rule 13

Minimizing energy loss from boiler blowdown can

save about 2% of a facility’s total energy use with an

average simple payback of less than 1 year.

26

Boiler Wise Rule 14

Removing a 1/32 inch deposit on boiler heat transfer

surfaces can decrease a boiler’s fuel use by 2%; removal

of a 1/8 inch deposit can decrease boiler fuel use by

over 8%. 

Appendix C Wise Rules Page 55

Appendix C 

Summary of Wise Rules

Boilers

Boiler Wise Rule 1

Effective boiler load management techniques, such 

as operating on high fire settings or installing smaller

boilers, can save over 7% of a typical facility’s total

energy use with an average simple payback of less

than 2 years. 

Boiler Wise Rule 2

Load management measures, including optimal

matching of boiler size and boiler load, can save 

as much as 50% of a boiler’s fuel use.

Boiler Wise Rule 3

An upgraded boiler maintenance program including

optimizing air-to-fuel ratio, burner maintenance, and

tube cleaning, can save about 2% of a facility’s total

energy use with an average simple payback of 5

months. 

Boiler Wise Rule 4

A comprehensive tune-up with precision testing

equipment to detect and correct excess air losses,

smoking, unburned fuel losses, sooting, and high

stack temperatures, can result in boiler fuel savings 

of 2% to 20%. 

Boiler Wise Rule 5

A 3% decrease in flue gas O2 typically produces 

boiler fuel savings of 2%. 

Boiler Wise Rule 6

Using over fire draft control systems to control excess

air can save 2% to 10% of a boiler’s fuel use with typical equipment costs of $1,500.
Boiler Wise Rule 15

Blowdown heat recovery is a proven technology that

can reduce a boiler’s fuel use by 2% to 5%.

Boiler Wise Rule 16

For every 11°F that the entering feedwater temperature

is increased, the boiler’s fuel use is reduced by 1%.

Boiler Wise Rule 17

Changing from manual blowdown control to automatic adjustment can reduce a boiler’s energy use by

2% to 3% and reduce blowdown water losses by up

to 20%.

Steam Systems

Steam Wise Rule 1

An effective steam trap maintenance program can 

save 3% of a facility’s total energy use with an average

simple payback of 2 months. 

Steam Wise Rule 2

An effective steam trap maintenance program can

reduce a boiler’s fuel use by 10% to 20%. 

Steam Wise Rule 3

Repairing steam system leaks can save 1% of a 

facility’s total energy use with an average simple 

payback of 3 months. 

Steam Wise Rule 4

A single high-pressure steam leak (125 psi) can result

in energy losses costing from $660 to $2,200 per year

(8,760 hrs). A single low-pressure steam leak (15 psi)

can result in energy losses costing $130 to $480 per

year (8,760 hrs). 

Steam Wise Rule 5

Insulating steam lines can save 1% of a facility’s total

energy use with an average simple payback of 10

months.

Steam Wise Rule 6

Vapor recompression saves 90% to 95% of the energy

needed to raise the steam to the same pressure in a

boiler.

Steam Wise Rule 7

Measures to reduce heat loss from condensate in a

steam system can save over 1% of a facility’s total

energy use with an average simple payback of 8

months. 

Process Heating

Process Heating Wise Rule 1

Proper heat containment can save about 2% of a

facility’s total energy use with an average simple 

payback of 9 months. 

Process Heating Wise Rule 2

Insulating a furnace with refractory fiber liners can

improve the thermal efficiency of the heating process

by up to 50%.

Process Heating Wise Rule 3

Recovering waste heat from furnaces, ovens, kilns,

and other equipment can save 5% of a typical facility’s

total energy use with an average simple payback of 16

months. 

Process Heating Wise Rule 4

Recovering waste heat through a recuperator can

reduce a kiln’s energy use by up to 30%; regenerators

can save up to 50%.

Process Heating Wise Rule 5

Each percent of moisture removed by air drying 

lumber reduces the kiln’s energy use by 50 to 85 Btu

per board foot.

Page 56 Wise Rules Appendix C
Process Heating Wise Rule 6

Variable fan speed control in the lumber industry 

can reduce dry kiln airflow by 20% and reduce the

kiln’s energy used during surface drying by as much 

as 50%.

Process Heating Wise Rule 7

Installing expert systems for kiln secondary control

can reduce a cement kiln’s energy use by up to 3%.14

Process Heating Wise Rule 8

New clinker cooler technologies that optimize heat

transfer conditions can reduce a cement kiln’s energy

use by up to 6%.

Process Heating Wise Rule 9

Direct firing with natural gas in place of indirect

steam heating has the potential to save 33% to 45%

of process heating energy use. Payback times may range

from a few months to 6 years.

Process Heating Wise Rule 10

Direct electric heating (infrared, microwave, or dielectric) can reduce process heating energy use by up to

80% with typical payback periods of 1 to 3 years.

Waste Heat Recovery and

Cogeneration

Heat Recovery/Cogen Wise Rule 1

Recovering waste heat can reduce a typical facility’s

total energy use by about 5% with an average simple

payback of 16 months. 

Heat Recovery/Cogen Wise Rule 2

Reducing net stack temperature (outlet temperature

minus inlet combustion air temperature) by 40°F is

estimated to reduce the boiler’s fuel use by 1% to 2%.

Heat Recovery/Cogen Wise Rule 3

Preheating furnace combustion air with recovered

waste heat can save up to 50% of the furnace’s energy

use. Heat Recovery/Cogen Table 1 summarizes 

typical fuel savings for a natural gas furnace. 

Heat Recovery/Cogen Wise Rule 4

Using an economizer to capture flue gas waste heat

and preheat boiler feedwater can reduce a boiler’s fuel

use by up to 5%.

Heat Recovery/Cogen Wise Rule 5

Removing a 1/32 inch deposit on boiler’s heat transfer

surfaces can reduce a boiler’s energy use by 2%;

removing a 1/8 inch deposit can reduce a boiler’s

energy use by over 8%.

Heat Recovery/Cogen Wise Rule 6

Gas turbines with heat recovery equipment typically

cost from $600 to $1,000/kW. Larger gas turbines

may be available for half the cost per kW. 

Heat Recovery/Cogen Wise Rule 7

A typical cogeneration project may reduce primary

energy consumption (including fuel inputs at off-site

powerplants for purchased electricity) for steam and

electricity generation by 10% to 15%.

Heat Recovery/Cogen Wise Rule 8

Cogeneration systems can save about 9% of a typical

facility’s primary fuel inputs for on-site energy use

(i.e., including fuel savings at off-site powerplants for

purchased electricity) with an average simple payback

of 34 months.19 (Savings are calculated by dividing

total energy savings, including powerplant inputs, by

total facility energy use.)

Appendix C Wise Rules Page 57
Compressed Air Systems

Compressed Air Wise Rule 1

Efficiency improvements can reduce compressed air 

system energy use by 20 to 50%.2

Compressed Air Wise Rule 2

Efficiency improvements to compressed air systems

can save approximately one-half percent of a facility’s

total energy use.

Compressed Air Wise Rule 3

Using cooler intake air for compressors can reduce

compressed air system energy use by 1% per 5°F reduction in intake air temperature.5 The payback period

for this measure is usually less than two years.

Compressed Air Wise Rule 4

Using cooler intake air for compressors can save

almost one-half percent of a facility’s total energy use

with an average simple payback of 5 months.

Compressed Air Wise Rule 5

Installing or adjusting unloading controls can reduce

compressed air system energy use by about 10%.

Compressed Air Wise Rule 6

Upgrading controls on screw air compressors can

reduce a facility’s total energy use by about 1% with

an average simple payback of 8 months.

Compressed Air Wise Rule 7

Reducing air compressor pressure can reduce a facility’s total energy use by about one-half percent with an

average simple payback of 4 months.

Compressed Air Wise Rule 8

Reducing air compressor pressure by 2 psi can reduce

compressor energy use by 1% (at 100 psi).

Compressed Air Wise Rule 9

Eliminating or reducing compressed air usage for certain activities can reduce a facility’s total energy use by

more than one-half percent, with an average simple

payback of 6 months.16

Compressed Air Wise Rule 10

Repairing air leaks can reduce compressed air system

energy use by 30% or more.

Compressed Air Wise Rule 11

Repairing air leaks can reduce a facility’s total energy

use by about one-half percent, with an average simple

payback of 3 months.

Compressed Air Wise Rule 12

It takes approximately 2.5 to 5.0 kWh to compress

1,000 ft3 of air to 100 psi.21,22 Each psi reduction in

compressed air loss from the distribution system (at

100 psi), reduces the compressor’s energy use by more

than one-half percent.

Compressed Air Wise Rule 13

Air compressor waste heat recovery can reduce a facility’s total energy use by about 1.8% with an average

simple payback of 10 months.

Compressed Air Wise Rule 14

For every 1 psi increase in air compressor pressure

gained by periodic filter changes, air compressor energy

use is reduced by about 0.5%. Changing dryer filters at

8 or 10 psi drop per filter can eliminate this waste.

Compressed Air Wise Rule 15

For every 11°F decrease in air compressor working temperature, gained by careful maintenance of intercoolers,

air compressor energy use will decreased by 1%.

Page 58 Wise Rules Appendix C
Process Cooling

Process Cooling Wise Rule 1

Installing energy efficient chillers and refrigeration

systems can save 1.2% of a facility’s total energy use

with an average simple payback of 23 months.

Process Cooling Wise Rule 2

“Free cooling” with cooling tower water can reduce a

facility’s total energy use by about 1 percent with an

average simple payback of 14 months.

Process Cooling Wise Rule 3

Free cooling can reduce cooling system energy use by as

much as 40% depending on location and load profile.

Process Cooling Wise Rule 4

Increasing chilled water temperature by 1°F reduces

chiller energy use by 0.6% to 2.5%.4 (See Process

Cooling Table 1 for data on specific chiller types.)

Process Cooling Wise Rule 5

Reducing condenser pressure by 10 psi can decrease

refrigeration system energy use per ton of refrigeration

(kW/ton) by about 6%.

Process Cooling Wise Rule 6

For each 1°F decrease in condenser cooling water

temperature, until optimal water temperature is

reached, there is a decrease in chiller energy use by 

up to 3.5%.

Process Cooling Wise Rule 7

Eliminating heat losses from leaks and improper

defrosting can reduce refrigeration system energy use

by 10% to 20%. 

Process Cooling Wise Rule 8

Freezing products in batches rather than continuously

can reduce freezing process energy use by up to 20%.

Process Cooling Wise Rule 9

Installing variable speed drives in place of constant

speed systems can reduce cooling system energy use

by 30% to 50%, depending on load profile.

Appendix C Wise Rules Page 59
Appendix D 

Key References

■ 3M Company, “Rules of Thumb: Quick Methods of

Evaluating Energy Reduction Opportunities,” 1992. 

■ Clevenger, L. and J. Hassel, “Case Study: From Jump

Start to High Gear—How DuPont is Cutting Costs by

Boosting Energy Efficiency,” Pollution Prevention Review,

Summer 1994, p. 301-312.

■ Garay, P.N., Handbook of Industrial Power and Steam

Systems, Fairmont Press.

■ Mercer, A., Learning from Experiences with Industrial

Drying Technologies, Centre for the Analysis and

Dissemination of Demonstrated Energy Technologies

(CADDET), 1994.

■ O'Callaghan, P., Energy Management, McGraw-Hill,

England, 1993.

■ Oregon State University, AIRMaster Compressed Air

System Audit and Analysis Software. To inquire about the

AIRMaster Software package, call the Energy Ideas

Clearinghouse at 1-800-373-2139.

■ Payne, F.W., Thompson, R.E., Efficient Boiler Operations

Sourcebook, 4th Edition, Fairmont Press, 1996.

■ Rutgers University, Office of Industrial Productivity &

Energy Assessment (OIPEA), Modern Industrial

Assessments: A Training Manual, Version 1.0b, (prepared

for the U.S. DOE Office of Industrial Technology and

the U.S. EPA, 1995). Available at: 

http://oipea-www.rutgers.edu/site_docs/pdfdocstm.html

■ Rutgers University OIPEA, “Useful Rules of Thumb for

Resource Conservation and Pollution Prevention,” 

March 1996. 

■ Taplin, H.R., Boiler Plant and Distribution System

Optimization Manual, Fairmont Press, 1991.

■ Talbott, E.M., Compressed Air Systems: A Guidebook on

Energy and Cost Savings, 2nd Edition, Fairmont Press,

1992.

■ Turner, W.C., Energy Management Handbook, 3rd

Edition, Fairmont Press, 1997

■ For assistance in preparing your Climate Wise Action

Plan or your Voluntary Greenhouse Gas Emissions

Report (Form EIA-1605), call the Climate Wise 

Wise Line at 1-800-459-WISE.

■ For information on the U.S. EPA Energy Star Programs,

call 1-888-STAR-YES.

■ For information on the U.S. EPA Waste Wise Program,

call 1-800-EPA-WISE.

■ For information on U.S. DOE Industrial Assessment

Centers, call 1-800-DOE-EREC.

■ For information on the U.S. DOE Motor Challenge

Program, call 1-800-862-2086.

■ For information on the U.S. DOE Compressed Air

Challenge, call 1-800-559-4776.

Appendix D Wise Rules Page 60

Key Resources