CHAPTER 15. UTILITY IMPACT ANALYSIS

TABLE OF CONTENTS

15.1 INTRODUCTION ......................................................................................................... 15-1

15.2 METHODOLOGY ........................................................................................................ 15-1

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CHAPTER 15. UTILITY IMPACT ANALYSIS

15.1 INTRODUCTION

In the utility impact analysis, DOE analyzes the changes in electric installed capacity and 

generation that result for each candidate standards case for the notice of proposed rulemaking 

(NOPR).

The utility impact analysis uses a variant of the DOE/Energy Information Administration 

(EIA)’s National Energy Modeling System (NEMS).a

 NEMS is a public domain, multi-sectored, 

partial equilibrium model of the U.S. energy sector. Each year, DOE/EIA uses NEMS to produce 

an energy forecast for the United States, the Annual Energy Outlook (AEO). DOE uses a variant 

of this model, referred to as NEMS-BT,b to account for selected utility impacts of energy 

conservation standards. DOE’s analysis consists of a comparison between model results for the 

most recent AEO Reference Case and for cases in which energy use is decremented to reflect the 

impact of standards. For the analysis of standards on residential dehumidifiers, DOE plans to use 

the version of NEMS based on AEO 2013.

1

NEMS-BT has a number of advantages that have led to its use in the analysis of energy 

conservation standards:

• NEMS-BT uses a set of assumptions that are well known and fairly transparent, 

due to the exposure and scrutiny each AEO receives. 

• NEMS-BT is updated each year, with each edition of the AEO, to reflect changes 

in energy prices, supply trends, regulations, etc.

• The comprehensiveness of NEMS-BT permits the modeling of interactions 

among the various energy supply and demand sectors.

15.2 METHODOLOGY

DOE uses NEMS-BT to estimate the marginal impacts of reduction in energy demand on 

the energy supply sector. In principle, marginal values should provide a better estimate of the 

actual impact of energy conservation standards. In practice, the numerical differences between 

a For more information on NEMS, refer to the U.S. Department of Energy, Energy Information Administration 

documentation. A useful summary is National Energy Modeling System: An Overview 2003, DOE/EIA-0581(2003), 

March, 2003. 

b DOE/EIA approves use of the name NEMS to describe only an official version of the model without any 

modification to code or data. Because this analysis entails some minor code modifications and the model is run 

under various policy scenarios that are variations on DOE/EIA assumptions, DOE refers to it by the name NEMSBT (BT is DOE’s Building Technologies Program, under whose aegis this work has been performed). 

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marginal and average values may turn out to be smaller than the intrinsic uncertainties in the 

AEO.

NEMS uses predicted growth in demand for each end use to build up a projection of the 

total electric system load growth. The system load shapes are converted internally to load 

duration curves, which are then used to estimate the most cost-effective additions to capacity. 

When electricity demand deviates from the AEO reference case, in general there are three interrelated effects: the annual generation (terawatt-hours (TWh)) from the stock of electric 

generating capacity changes, the total generation capacity itself (gigawatts (GW)) may change, 

and the mix of capacity by fuel type may change. Each of these effects can vary for different 

types of end use. The change in total generating capacity is sensitive to the degree to which the 

end-use is peak coincident, while the capacity mix is sensitive to the hourly load shape 

associated with the end use.

To model the impact of a standard, DOE inputs a reduction to annual energy demand for 

the corresponding end use in the appropriate start year. The NEMS-BT model is run with the 

decremented energy demand to determine the modified build-out of capacity and total 

generation. Regional effects of a standard can be accounted for by defining the energy demand 

decrement as a function of census division. 

The output of the NEMS-BT analysis includes the effective marginal heat rate (ratio of 

the change in fuel consumption in quadrillion British thermal units (quads) to the change in 

generation in TWh), and the capacity reduction by fuel type for a given reduction in total 

generation. DOE uses the site energy savings multiplied by a transmission and distribution 

(T&D) loss factor to estimate the reduction in generation for each trial standard level (TSL). The 

relationship between a reductionc in electricity generation (TWh) and the reduction in capacity 

(GW) is estimated based on the output of NEMS-BT model runs using the end-use specific 

energy demand decrement. Details on the approach used may be found in Coughlin (2012).2

NEMS-BT provides output for the following capacity types: coal, nuclear, 

combined cycle (natural gas), renewable sources, oil and natural gas steam, 

combustion turbine/diesel, pumped storage, fuel cells, and distributed generation (natural gas). 

DOE grouped oil and natural gas steam and combustion turbine/diesel into a “peaking” category, 

and grouped pumped storage, fuel cells, and distributed generation (natural gas) into an “other” 

category.

c These reductions are defined relative to the AEO Reference case.

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REFERENCES

1. Energy Information Administration, Annual Energy Outlook 2013 with Projections to 

2040, 2013. Washington, DC. <http://www.eia.doe.gov/oiaf/aeo/>

2. Coughlin, K., H. Shen, P. Chan, B. McDevitt, and A. Sturges, Marginal Utility Sector 

Impacts of Reduced Electricity Demand, 2012. 

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