A term that is meant to try and describe saved electricity that by means of energy efficiency was not created, used or wasted. It is not yet a real physical amount or a measureable quantity, simply an attempt to popularize the thinking that saving electricity and making efficiency-efforts more fun and useful.
The potential in energy efficiency efforts in U.S. of reducing peak demand on electriciy is possibly as large as 60 nuclear power plants of the infamous Chernobyl-sized plant.[1] (1989)
Compare this idea with the popular Benjamin Franklin quote: A penny saved is a penny earned[2]
Links
CCNR.org[3]
RMI.org[4]
Wikipedia/Negawatt_power[5]