No. of Recommendations: 3
Setting back your thermostat incontrovertibly saves energy - unless you do it stupidly.

For heat pump systems you can do it exceptionally stupidly, because they heat differently than gas, oil, and hot water systems. That's because heat pumps work so slowly that they also employ resistance heating (those wires that glow red in a space heater) to bring temperatures up quickly, since homeowners don't want to wait four hours if they're chilly. If you dial back the thermostat you certainly do shut off the heat pump, but when you turn it back on - unless you ratchet up the heat slowly - you insist on resistance heating which is the most expensive kind.

Set back thermostats for heat pumps call for a 2 degree increment, and when that is achieved call for another 2, and so on, until the requested temperature is achieved. Any more than that 2 degree delta and you've more than negated any savings. A set-back thermostat for heat pumps will do this invisibly, automatically, but you must give them enough time to get there - several hours, at least.

That said, in all other cases you save money, more with poorly insulated homes, less with better insulated ones, but you ALWAYS save. That's because the temperature loss is proportional to the difference between inside and outside. To exaggerate the case: if it's 40 degrees outside and you set the thermostat at 40 degrees, you lose NO (additional) heat all night because the furnace never comes in. (Again, exaggerate and pretend you keep it there for a week or a month. Truly huge savings). If you chose, instead to keep the temperature at 70, you would surely use lots of energy to maintain that temperature over time. Yes, it takes energy to bring a room or house back to temperature, but not as much as you would have wasted keeping it at that temperature for an unoccupied or unused room.

(Again the reason is esoteric, since the amount if energy consumed is proportional to the delta between the two extremes. But getting to the higher temperature takes less energy than maintaining that temperature over time. Anyone with even a small knowledge of thermodynamics will agree, even if it seems "wrong" to lay people.)
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