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Community and Q&A

Wrong to turn thermostat down at night?

jkstew | Posted in Energy Efficiency and Durability on

I read one of those click baity things at The Weather Channel’s website, “Six Mistakes to Avoid This Winter”. Most of the six things are common sense that I understand, however suggestion #2 says that turning your thermostat way down at night is a money-wasting mistake.

https://weather.com/home-garden/seasonal-renewal/news/6-heating-mistakes-commonly-made-20141028#/2

They don’t give any guidance to what an “extreme” at night setting might be but the picture shows 62 F which just happens to be my at night setting. Are they right? If so, what setting should I use? I usually set at 62 at night and wake up to 70 F.

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Replies

  1. Jon_R | | #1

    It depends on the heat source and/or if you have variable rates. For me (nat gas, forced air), it saves energy and is more comfortable.

  2. Dana1 | | #2

    With the typically ridiculously oversized equipment found in most US homes a deep overnight setback could save some money. The crummier the house (more air leaky, less insulation) the more the savings would be.

    With a right sized modulating system the savings could be negative, if the heating system runs at lower efficiency when running full-tilt during a recovery ramp. The extreme case would be a modulating heat pump with resistance heat back up that comes on if the thermostat isn't satisfied within some pre-set amount of time. Modulating in might only run a COP of 2-3 at night, but with heat strips engaged during a recovery ramp it would be less than 1.5, more than erasing any savings that might have occurred due to the lower heat loss at a lower indoor temp.

  3. GBA Editor
    Martin Holladay | | #3

    Jay,
    As usual, this list of energy-saving tips provides little context, and provides advice that applies to some, but not all, homeowners.

    If you live in a house with an air-source heat pump, don't set back your thermostat at night.

    If your house has a furnace or boiler fueled by natural gas, propane, or oil -- especially an older heating appliance -- nighttime setbacks usually save you money, especially if your house is leaky and poorly insulated (or your energy bills are high).

    The better your home's thermal envelope, the less thermostat setbacks will save.

  4. user-5946022 | | #4

    Jay S - The reason for the small electric heater in the storage space is to keep the water pipes to and from the water heater from freezing. In an apartment, that heater should not be controllable by the tenant, and should only come on at about 38-40F (depending upon recovery rate). If, as a tenant you can control it, you turn it off, and your pipes freeze, your cost will be a whole lot more than the heat...

    The exterior shed might be separate from the living area - is the wall between them insulated? Is that storage space vented?

  5. jkstew | | #5

    CL, that makes sense about the electric heater in the shed. Whenever I go out there the little shed is fairly warm. The furnace tends to keep the small space above freezing temps during the day. I've never seen the electric space heater on during the day so I assume it only comes on at night. I just know that my electric bill starts to get out of hand when the temps really drop and I'm guessing that's the problem. The storage shed seems to be well insulated. I don't know what insulation may be between the shed and the apt. The shed is vented by the gas furnace and gas tankless water heater.

  6. jkstew | | #6

    Gentlemen, thanks for your comments. I recently moved into a LEED Platinum certified apt. that just opened a few months ago. I'm in zone 6b and my 620 sq ft. apt has natural gas forced air heat. The heater, ERV, and tankless hot water heater are outside the living area in a small storage space adjacent to the apt. I'm still experimenting with settings and have no previous winters here as a yardstick to go by. The storage space that houses the HVAC has a small electric heater to keep the space warm for some reason. I think that heater may be costing me a lot of money if I turn down the heat. The outside temps are in the single digits for highs and well below zero for lows at night. I had been lowering my heat to 62 F at night, which keeps the gas heater off effectively, but then that small electric heater outside in the shed starts costing me. I'll continue to experiment with nightime settings.

  7. JC72 | | #7

    We turn off the downstairs zone (drops to 58 degrees by early AM) in order to keep heat in the bedrooms upstairs. Otherwise heat from downstairs will collect in the upstairs hallway near the thermostat and the 2nd floor zone will never turn on.

    The house leaks like a colander so we're probably saving some $$. We could fix it, but it would require a DER and $80k

  8. Chaubenee | | #8

    All I know I have gotten used to dropping my stat lower and lower at night as I get older. It goes down to 58F at sleep time now and it is for COMFORT. People think I live in a morgue, but I breathe better and am more able to get a better night's rest without the dry hot air blasting me. During the day we are at the same temps and my dogs always seemed more comfy too, seeing as they wear fur coats 24/7.In the evenings we turn it up to about 66 simply because my wife feels cold if I don't. Most people I know like low seventies.

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