Romm, Joseph J.   Industrial Management. 
New York: Kodansha America, 1994
ISBN 1568360371

Page 72

Energy efficiency means providing the same or better energy services using less energy; indeed, the latest efficient technology typically provides more pleasing light, more reliable production, and greater comfort and control. In contrast, energy conservation achieves lower energy use by giving up some quality of service. Energy conservation is turning down the thermostat and donning a sweater. Energy efficiency is insulating a building or using new high-performance windows.