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Energy Efficiency: Definition   Stairs) 

"Take the Stairs--Be More Energy Efficient"

Person A  interprets the sign as the "true" definition of energy efficiency. To Person A, the elevator is not being used. He is still getting to where he wants to go and using less energy in doing so.

Person B considers the fact that she is not getting to where she is going with the same ease. She does not believe that she is being energy efficient, but instead she believes that she is "conserving energy" at a reduced level of service—she has to walk instead of ride.

When it comes to trying to define "to be energy efficient" or "energy efficiency", there does not seem to be a single commonly-accepted definition of energy efficiency. Along the lines of Person B’s thinking, it is generally thought that an increase in energy efficiency is when either energy inputs are reduced for a given level of service, or there are increased or enhanced services for a given amount of energy inputs.

When EIA asked participants in energy-efficiency workshops to define "energy efficiency," participant definitions reflected two different perspectives: either (1) a service perspective or (2) a mechanistic, strict intensity, perspective.

Some participants believed that energy-efficiency indicators could measure some kind of economic well-being, and suggested that a wide range of indicators would offer insight into the "ordinary business of life" and the relationships, causes, and opportunities in observed trends. Another suggested concept of efficiency is a strict technological (equipment-based) concept. This concept cannot be strictly measured by broad intensities, because intensities tend to carry structural and behavioral components.  Alternatively, some participants believe that differentiating between intensity and efficiency is not possible. While others use complex methodology to separate out the activity and structural effects with the remaining unexplained portion considered to be an approximate to the energy efficiency effects.

Most of what is defined as energy efficiency is actually energy intensity. Energy intensity is the ratio of energy consumption to some measure of demand for energy services—what we call a demand indicator. However, at best, energy-intensity measures are a rough surrogate for energy efficiency. This is because energy intensity may mask structural and behavioral changes that do not represent "true" efficiency improvements such a shift away from energy-intensive industries.  [See "Energy-Efficiency Measurement: Discussion"].                

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For specific questions about the "Energy Efficiency Definition", please contact:

Stephanie J. Battles

Phone: 202-586-7237
Fax:  202-586-0018

Release Date:  June 19, 2000 

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Page last modified on 02/06/2003 .
URL:   http://www.eia.gov/emeu/efficiency/definition.htm