What is the difference between energy conservation and energy efficiency?

With energy efficiency, you don’t have to sacrifice comfort to save energy. Energy conservation involves a change in behavior to save energy (turning off the lights, powering down computers and electronic equipment at night, lowering the thermostat in winter and raising it in summer). Energy efficiency means physical upgrades like replacing worn out weather stripping, repairing leaking ductwork, adding insulation, replacing inefficient lighting and appliances, etc.