This paper describes a methodology that EPRI has developed to model the marginal carbon dioxide (CO2) emissions impact of energy efficiency. Though energy efficiency is intuitively recognized to reduce carbon emissions, one barrier to its broader application is the lack of precision in attributing emissions reductions to specific program activities. Coarse estimates based on utilities' average emissions factors, while straightforward to calculate, do not provide enough specificity on emissions reductions at the margin.
Recognizing this barrier, EPRI has been conducting research over the past several years to apply an electricity production simulation model to quantify the impact of energy efficiency on marginal CO2 intensities (metric tons of CO2 avoided per MWh of energy efficiency savings) that are specific to both end-use and region. These intensity values can be applied to more accurately translate energy savings from energy efficiency activities into CO2 emissions reductions, by taking into account both temporal variation — i.e. when the savings occur based on end-use load shapes — and regional variation — i.e. where the savings occur based on differences in generation mix by region — as each factor impacts the avoided dispatch of generation from which emissions reductions result. EPRI offers this approach for consideration as an industry-standard methodology that electric utilities, regulators, regional planners, and policymakers can apply to more accurately assess the environmental impact of implementing specific types of end-use energy efficiency programs.
Moreover, EPRI's modeling approach strikes a balance between analytical rigor for precision, and ease-of-use for practical application. Results from the EPRI simulation model are conveniently condensed into CO2 emissions intensity values, specific to U.S. region and type of end-use. To quantify resulting emissions reductions, energy savings from a particular type of energy efficiency measure, such as a more efficient residential lighting or commercial space cooling program, can be simply multiplied by the corresponding intensity value obtained from the model. EPRI has also developed for its members an associated calculator tool to help them conduct more customized calculations of the emissions reductions impacts of their energy efficiency programs.
In summary, this EPRI approach provides a sound framework for utility industry stakeholders to establish a societal business case for energy efficiency and new technological innovations therein.