RGGI Emissions Trends 

May 2011

Emissions from power plants in the 

Regional Greenhouse Gas Initiative 

(RGGI) increased slightly in 2010, but 

remained well below the regional emissions 

cap. The 2010 increase was due primarily 

to a hotter summer and higher electricity 

demand for air conditioning. The 

persistence of low 2010 emissions in 

relation to the cap was a consequence 

primarily of fuel-switching to natural gas, 

increased generation from non-emitting 

sources, stable electricity consumption, and 

weak economic conditions in the region.

Summary of Key Findings: 

Between 2009 and 2010 emissions increased 10.9%, but total 2010 emissions remain 27% below 

the RGGI cap.

Emissions declines are primarily driven by low prices for natural gas, which emits less carbon dioxide 

(CO2) than other fossil fuels in electricity generation. This unanticipated increase in natural gas 

utilization (displacing coal and fuel oil generation) demonstrates that significant emissions 

reductions can be delivered rapidly and cheaply with existing infrastructure. 

Non-fossil generation – such as hydroelectric, wind, and nuclear power – is displacing highCO2 generation from coal and oil, and increases in non-emitting generation will continue to 

reduce emissions in the years ahead.

While the economic downturn, along with expanding energy efficiency program investments, have

reduced electricity consumption and emissions over the past two years, stable electricity demand 

during the preceding period of economic growth (2001-2007) suggests that the linkage between 

economic growth and emissions has weakened, and the economic rebound may not increase 

emissions significantly.

Emissions Data 

Carbon dioxide emissions from RGGI power plants in 2010 totaled 137,174,260 tons, a 10.9% increase 

from 2009 levels (123,718,594 tons) but remained 27.1% below the regional cap of 188,076,976 tons 

(Figure 1). 

Emissions data made available by the RGGI member states and compiled by RGGI, Inc through the 

CO2 Allowance Tracking System (RGGI-COATS), formed the basis for the analysis. 1 

 

1 Emissions data available at: https://rggi-coats.org/eats/rggi/, “Public Reports”. Three facilities listed incomplete data 

for 2010: Devon (CT), AES Greenidge (NY), and Project Orange Facility (NY). Devon and AES Greenidge list higher 

emissions in the incomplete 2010 quarter than in corresponding 2009 quarter, and the incomplete 2010 data was used to 

provide a conservatively high estimate of 2010 emissions. In the absence of any data from Project Orange Facility in 

RGGI at a Glance:

10 States (ME, MA, NH, VT, RI, CT, NY, NJ, DE and MD)

Applies to all fossil fuel-fired power plants 25 MW or 

greater

Went into effect Jan 1, 2009 

11th auction conducted on March 9, 2011

Initial regional cap is 188 million tons CO2

Cap is two-phase: 

o Stabilization at initial level for 2009-2014.

o 2.5% reduction per year 2015-2018 for total 10% 

reduction

3 year compliance period; first permits due 3/1/2012. 
2

Figure 1: RGGI Facility CO2 Emissions through 2010

Emissions Drivers

Carbon dioxide emissions in the RGGI region are driven by a number of factors, some of which are 

interrelated. In this report, emissions drivers are categorized under four headings: 

Energy Prices & Natural Gas Generation – describing the impact of cheap, low-emissions 

natural gas on the regional electricity generation mix; 

Non-Fossil Fuel Generation – describing how increased generation from renewable and 

nuclear sources has decreased the utilization of high-emissions coal and gas power plants;

Economic Conditions & Electricity Consumption – describing the extent to which the 

recession has decreased electric demand; noting that economic growth and emissions are not as 

closely linked as commonly assumed; and

Weather – describing the impact of weather conditions, (largely air-conditioning) on electricity 

demand and emissions.

 

2010 q4, 2009 q4 data was used. In total, emissions from these three plants comprised 0.5% of RGGI emissions in 

2009, and as such inconsistencies should not affect final 2010 emissions significantly.
3

Energy Prices & Natural Gas Generation

Electric sector emissions are largely determined by the type of fuel used to generate electricity, and 

increased utilization of low-emissions natural gas has decreased RGGI region emissions significantly. 

The relative prices of residual fuel and natural gas are particularly important in the RGGI region, as 

significant capacity exists to generate power from either fuel, facilitating the utilization of whichever fuel 

is cheapest. For the majority of the past 5 years natural gas has been significantly lower priced (Figure 2).

Figure 2: National Spot Prices for Residual Fuel and Natural Gas 

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Jan-00 Jan-01 Jan-02 Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 Jan-09 Jan-10 Jan-11

Wholesale / Wellhead Prices ($/MMBTU)

Natural Gas

Source: EIA Residual Fuel
4

Low natural gas prices have led to decreased utilization of residual fuel and coal generation. (Coal prices 

vary across the region, but have generally increased since 2003, according to EIA.) In the RGGI region 

residual fuel generation in 2010 was down 46% from 2009 levels and 95% from 2005 levels, while coal 

generation increased 2% from 2009 levels, yet decreased 30% from 2005 levels (Figure 3). Meanwhile, 

natural gas generation continued to increase in 2010, up 18% from 2009 levels and up 35% from 2005.

Figure 3: RGGI Region Electric Generation from Natural Gas, Coal and Residual Fuels

Fuel switching from coal and oil to lower-carbon natural gas has had a significant impact on regional 

emissions. To produce the same amount of heat, natural gas emits 44% less carbon than coal and 33% 

less carbon than fuel oil,2 and natural gas plants are typically more efficient. Using the average efficiency 

of each type of generation,3 it can be estimated that since 2005 (when the RGGI cap was established), 

emissions from residual fuel and coal generation have decreased by approximately 67.2 million tons, while 

emissions from natural gas generation have increased by approximately 17.4 million tons, for a net decrease

of 49.8 million tons.

 

2 Carbon emissions factors for natural gas (117.0 lbs CO2/MMBtu), residual fuel oil (173.7 lbs CO2/MMBtu) and coal 

(210.0 lbs CO2/MMBtu) from EIA: www.eia.doe.gov/oiaf/1605/excel/Fuel%20Emission%20Factors.xls

3 EIA average operating heat rate for natural gas (8,305 Btu/kWh), residual fuel (11,015 Btu/kWh) and coal (10,387 

Btu/kWh) available at: http://www.eia.doe.gov/cneaf/electricity/epa/epat5p3.html

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2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

Generation from Residual Fuels (GWh)

Generation from Natural Gas and Coal (GWh)

Natural Gas

Coal

Residual Fuel

Source: EIA

Since the RGGI cap was established in 

2005, generation from residual fuels and 

coal has decreased significantly, while 

natural gas generation has increased
5

Non-Fossil Fuel Generation

Non-fossil fuel electricity – including nuclear, hydro, wind, and other forms of renewable energy – is 

displacing fossil fuel generation and reducing emissions across the region. Data indicate that non-fossil 

fuel generation increased 4.1% from 2008 to 2009, and has risen 15% since 2001 (Figure 5). 

Figure 5: RGGI Region Electricity Production from Non-Fossil Sources

Between 2001 and 2010 annual non-fossil generation in the RGGI region has increased by over 18,500 

GWh, with about 6,700 GWh of generation coming online since 2005. Of this 6,700 GWh of new nonfossil generation, 3,240 GWh came from wind, 3,890 GWh came from nuclear, and 700 GWh came 

from landfill gas. Some of the increase in non-emitting generation was offset by a 3,850 GWh decline in 

hydro output in from 2009 to 2010, which contributed to higher 2010 emissions. However, overall

trends in recent years show that non-emitting generation is generally displacing fossil-based electricity, 

and is another driver behind emissions declines in the RGGI region.4 

The expansion of non-emitting generation appears likely to continue in years ahead. The Federal Energy 

Information Administration (EIA) predicts that renewable and nuclear generation will continue to 

increase nationwide in the near term, in addition to natural gas generation.

5 Additionally, all 10 RGGI 

states have Renewable Portfolio Standards that require electric utilities to procure increasing quantities of 

renewable electricity, ensuring continuing growth of renewable generation in the region.6

 

4 Based a weighted average of emissions intensity for oil and coal generation coming off line since 2005, in 2010 this 

non-emitting generation avoided approximately 6.8 million tons of CO2 that would have been emitted to produce an 

equivalent amount of electricity from oil and coal.

5 EIA, 2011, Annual Energy Outlook 2011 Early Release Overview, Available at: http://www.eia.gov/forecasts/aeo/

6 For additional information on State Renewable Energy Portfolios see the Department of Energy’s EERE State 

Activities & Partnerships, Available at: http://apps1.eere.energy.gov/states/maps/renewable_portfolio_states.cfm

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2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 Annual Non-Fossil Generation (GWH)

Wood Biomass

Landfill Gas

Wind

Nuclear

Hydro

Source: EIA
6

Overall Generation Trends

Electric generation in the RGGI region has reduced in carbon intensity over the last 5 years, due to 

increased generation from natural gas, nuclear, and renewable sources and decreased output from highercarbon coal and residual fuel plants (Figure 6). With the exception of steady, incremental growth in wind 

capacity, this decline in electric sector emissions has occurred without the addition of significant new 

capacity or capital expenditures. This low-cost transition to lower regional emissions suggests that 

decreasing emissions may be far more cost-effective than commonly assumed.

Figure 6: RGGI Generation by Fuel Type

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2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

Annual Generation (GWH)

Year

Other

Other Renewables

Petroleum Products

Hydroelectric

Coal

Nuclear

Natural Gas

Source: EIA
7

Economic Conditions & Electricity Consumption

Economic conditions and electricity consumption are significant drivers of RGGI region emissions, but 

stable electricity demand during recent periods of economic growth suggests that emissions may remain 

low even as the economy recovers from its recent downturn. Electricity demand has historically been 

tied to economic growth, with electricity consumption – and related emissions – increasing during 

periods of economic expansion, and decreasing in economic downturns. RGGI region economies 

expanded for the majority of the last decade, with the economic downturn reversing this trend in 2008-

2009, as evidenced by coincident indexes from the Federal Reserve Bank of Philadelphia (Figure 7).7

Figure 7: RGGI Region Economic Conditions

 

7 See: http://www.philadelphiafed.org/research-and-data/regional-economy/indexes/coincident/

120.00

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190.00

200.00 Coincident Historic Economic Indicators

CT

D E

ME

MD

MA

NH

NJ

NY

RI

V T
8

While the economic downturn (and attendant decrease in electricity consumption) likely contributed to 

emissions declines, the direct link between economic growth and increases in electricity consumption 

and emissions appears to be weakening. Electricity consumption increased only slightly in the early part 

of the decade, and remained stable during the economic growth period from 2003-2007 (Figure 8). This 

suggests that improved energy efficiency and successful energy savings programs may have broken the 

link between economic growth and emissions growth. While the extent of this trend remains unclear, 

emissions may remain low when the economy recovers, as efficiency investments increase and low- or 

non-emitting generation supplies an increasing portion of the regional energy mix.

Figure 8: RGGI Electricity Consumption 

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2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 Annual Electricity Sales (TWh)

Year

V T

RI

NY

NJ

NH

ME

MD

MA

D E

CT

Source: EIA
9

Weather

Hot and humid summer weather leads to greater electricity consumption for air conditioning, and cold 

winter weather increases natural gas and heating oil consumption (only a small percentage of buildings in 

the region are heated with electricity). As home heating fuels are not covered under RGGI, ENE uses 

the temperature-humidity index (THI) to gauge the impacts of weather on electricity consumption and 

emissions. 

The summer of 2010 was more hot and humid than the last several years (Figure 9).8 Hotter, more 

humid weather increased demand for air conditioning, thus increasing electricity demand and emissions. 

Figure 9: RGGI Weighted Temperature-Humidity Index

 

8 2010 weather data from Delaware was unavailable at the time of publication.

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2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 Weighted Temperature-Humidity Index

Baltimore, MD

Boston, MA

Burlington, VT

Dover, DE

Windsor Locks, CT

Manchester, NH

New York, NY

Newark, NJ

Providence, RI

Source: ENE Analysis of NCDC Data
10

Emissions Leakage

The addition of RGGI allowance costs to electric generation prices does not appear to be causing 

significant leakage of emissions to generation sources outside of the RGGI region. Since RGGI began 

adding carbon costs to electricity prices on January 1, 2009, electricity sales have increased by 0.2%, while 

generation decreased by only 0.7%. In 2009 – when RGGI allowance prices were higher – sales were 

down 4.4% from 2008 levels while generation was down 3.5%, indicating a modest decrease in imports 

before the modest increase in 2010 (Figure 10). 

Figure 10: RGGI Region Electricity Trends

Conclusion

Due primarily to a hot and humid summer, 2010 RGGI emissions increased from 2009, but remain well 

below the regional cap due to low cost natural gas, increased non-emitting generation, more efficient use 

of electricity, and – to a lesser extent – economic trends and mild summer weather. The significant 

emissions decline in the RGGI region suggests that fundamental shifts in the power sector may mean 

lower emissions are here to stay for the foreseeable future.

For Further Information: 

Derek Murrow, Energy & Climate Policy Director, (203) 285-1946, dmurrow@env-ne.org 

Peter Shattuck, Carbon Markets Policy Analyst, (617) 742-0054, pshattuck@env-ne.org

8 Summer Street, PO Box 583 Rockport, ME 04856 (207) 236-6470 admin@env-ne.org

Portland, ME / Boston, MA / Providence, RI / Hartford, CT / 

Ottawa, ON, Canada | www.env-ne.org | Daniel L. Sosland, Executive Director

Environment Northeast is a nonprofit research and advocacy organization focusing on the Northeastern United States and Eastern Canada. Our 

mission is to address large-scale environmental challenges that threaten regional ecosystems, human health, or the management of significant natural 

resources. We use policy analysis, collaborative problem solving, and advocacy to advance the environmental and economic sustainability of the 

region.

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` 2005 2006 2007 2008 2009 2010

Annual RGGI Region Electricity Trend (TWh)

EIA Sales

EIA Generation

Source: Energy Information Administration 

RGGI Start