Does Turning the Heat Off During the Day Save More Than Leaving It Steady?

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The Old Myth: Does It Cost More to Reheat a Cold House?

A common belief is that it takes so much energy to reheat a cooled-down house that any savings from turning the heat down are cancelled out. For a standard gas furnace, this is not true. The physics is simple: the colder your house is relative to outside, the faster it loses heat. So a house held at 21C all day loses heat steadily the whole time, while a house allowed to drift down to 17C loses heat more slowly during those hours. The energy used to warm it back up is less than the energy you would have spent holding it warm the entire time.

The U.S. Department of Energy has long estimated meaningful annual savings from setting a furnace-heated home back by several degrees for roughly eight hours a day. The exact number varies with your insulation, climate, and how big a setback you use, but the direction is clear: for a furnace, setbacks save money.

Heat Pumps Are the Big Exception

If you heat with a heat pump (increasingly common in Metro Vancouver thanks to CleanBC and FortisBC rebate programs), the advice flips. Heat pumps run most efficiently when they hold a steady temperature and heat gently. When you let the house drop several degrees and then demand a big recovery, many heat pumps kick on their backup electric-resistance heat strips, which are expensive to run. That recovery cost can wipe out or exceed your setback savings.

With a heat pump, the general rule is: leave it fairly steady, or use only a small setback of a degree or two. If you have a smart or heat-pump-aware thermostat, it can manage the recovery gradually so the backup heat does not engage. Do not treat a heat pump like a gas furnace on this.

What This Looks Like in Practice

• Gas furnace, away all day: set back about 3 to 5C while you are out, and let it come back up before you return. This saves the most.
• Heat pump: keep it steady, or use a setback of only 1 to 2C. Avoid deep drops that trigger backup heat.
• Do not turn the heat fully off in a Metro Vancouver winter, especially if pipes run through unheated crawlspaces or exterior walls. A modest setback is the goal, not zero heat.
• A programmable or smart thermostat makes this automatic, so you are not relying on memory to adjust it twice a day.

Why the Savings Are Smaller in Mild Vancouver Winters

Metro Vancouver has a relatively mild, damp winter compared with the rest of Canada. Because the gap between your indoor temperature and the outdoor temperature is smaller here than in, say, the Prairies, the heat loss you avoid with a setback is also smaller. You will still save with a furnace, just not as dramatically as someone in a colder climate. The upside is that our mild winters make heat pumps a great fit, and with a heat pump the smarter move is steady operation rather than big daily swings.

If you are not sure whether you are on a furnace or a heat pump, or your setbacks do not seem to be saving anything, CANRO can look at your system and thermostat settings during a diagnostic visit and give you a free written quote for any adjustments. Call (604) 359-1081 or email info@canroheat.ca. We have served Metro Vancouver since 1999.

Frequently asked questions

Reviewed by the CANRO Heating & Cooling service team — July 07, 2026. Technical Safety BC gas licence LGA0043870 · boiler licence LBP0046450 · Red Seal certified · WorkSafeBC and liability insured · 4.9★ from 85+ Google reviews · serving Metro Vancouver since 1999 · (604) 359-1081.