Seed Magazine highlights the word Negawatt:
\né-gə-wät\ n: A measure of the avoided use or the conservation of a unit of energy.
Wikipedia goes into more detail:
By investing to reduce electricity demand instead of investing to increase electricity generation capacity, this “virtual generation” method can supply growth of supply by improving the efficiency of existing electrical equipment rather than by building new power stations.
Energy consumers may also reduce energy consumption during peak, hours to “generate” negawatts – hypothetical tradeable units of saved energy.
A similar concept applies to energy, with potential consumers being rewarded for lowering consumption at any time, rather than just at peak times: this could then be labeled negajoules or negawatt-hours.