Updated August 22, 2026

Is It Cheaper to Leave Heating On All Day?

The Definitive Answer — With Real Energy Data

Direct Answer

No — it is almost always cheaper to set your heating back when rooms are unoccupied. Physics proves it, and the Department of Energy puts a number on it: turning the thermostat back 7–10°F for 8 hours a day saves about 10% a year on heating and cooling.

✓Saving figure from the US Department of Energy’s thermostat guidance; the percentages further down are heat-loss physics, worked from a 70°F setpoint on a 30°F day

The Physics

Why Leaving Heating On Costs More

Newton's Law of Cooling

The rate at which a house loses heat is directly proportional to the temperature difference between inside and outside. A house at 70°F on a 30°F day (40°F difference) loses heat exactly twice as fast as a house at 50°F on the same day (20°F difference). Keeping your home warmer while you are away means it is constantly losing heat faster — requiring more energy to maintain that temperature.

The "Reheating Uses More Energy" Myth

The most common argument for leaving heating on is that reheating a cold house uses more energy. This is false. Yes, more energy flows in during the reheat phase — but the house also lost much less energy while it was cooler. The total energy used to maintain 68°F all day always exceeds the energy used to let it drop to 58°F and reheat before you return. The Department of Energy confirms this directly.

The Only Exception: Heat Pumps in Extreme Cold

Cold-climate heat pumps (below 20°F outdoor temperatures) operate more efficiently at steady low output than cycling on and off at full power. In these conditions, a 2–4°F setback rather than a full 8–10°F setback may be more efficient. However, even in these cases, setbacks during long absences (8+ hours) still save energy.

Scenarios

What to Do In Every Situation

Work day — 8 hrs away, 8°F setback

Turn it down — the biggest routine saving

~20%

less heat loss while held

The larger half of DOE's ~10%/year

Short errand — 1–2 hrs away

A 2–3°F setback is all the house will manage

~8%

less heat loss while held

Barely worth changing the setting

Weekend away — 48 hrs at 50°F

Set 50°F — low enough to save, high enough to protect pipes

~50%

less heat loss while held

Roughly halves the weekend's heat loss

Overnight while sleeping

Set back 6–8°F — better sleeping temperature anyway

~18%

less heat loss while held

The other half of DOE's ~10%/year

Working from home all day

Setbacks cannot help; heat the room you work in and let the rest sit cooler

less heat loss while held

No unoccupied hours to set back

Best setback schedule: Set to 60–62°F while at work and asleep — that is the 7–10°F setback DOE’s ~10%-a-year figure is based on. Schedule the thermostat to begin warming about 30 minutes before you wake and 30 minutes before you get home, so you keep nearly all of the saving and still walk into a warm house. If you heat with a heat pump, use a shallower setback: it recovers more slowly and may fall back on resistance backup heat to catch up.

FAQ

Heating Schedule Questions Answered

Is it cheaper to leave the heating on all day?

No — it is cheaper to turn the heating down when rooms are unoccupied and let the temperature drop. The rate at which a house loses heat is proportional to the difference between indoor and outdoor temperature, so a cooler house loses less heat every minute it sits cooler. The energy needed to reheat it never exceeds what you saved while it was cool.

Is it cheaper to leave heating on low or turn it on and off?

Turning it down is cheaper for any absence long enough for the house to actually cool — in practice a few hours or more. For a short errand a 2–3°F setback is all you will get value from, because the house barely moves. For a working day, setting back to 60–62°F is the standard advice, and the Department of Energy puts the whole-year saving from a 7–10°F setback held 8 hours a day at about 10% of heating and cooling costs.

How much do I save by turning the heating down when I leave?

The Department of Energy's published figure is about 10% a year on heating and cooling for turning the thermostat back 7–10°F for 8 hours a day. On EIA's forecast household heating expenditure for winter 2025–26 that is roughly $64 a season for a gas-heated home and about $139 for one heated with oil. Ignore the "3% per degree of setback, per hour" rule that circulates online: multiplied out over an 8°F setback and a 10-hour day it would claim a 240% saving, which is impossible. The examples quoted alongside it are really 3% per degree in total, and even that is not a figure DOE publishes.

Does leaving heating on low all day damage your boiler or furnace?

Modern boilers and furnaces are designed for frequent cycling and are not damaged by turning on and off. Heat pumps are somewhat more efficient running steadily at low capacity than cycling at full output in very cold weather, which is why a deep setback is less useful with a heat pump than with a furnace — but for a full working day away, a setback still saves energy.

Is It Cheaper to Leave Heating On All Day?

Why Leaving Heating On Costs More

Newton's Law of Cooling

The "Reheating Uses More Energy" Myth

The Only Exception: Heat Pumps in Extreme Cold

What to Do In Every Situation

Heating Schedule Questions Answered

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