What Temperature to Set: Summer, Winter and Away

By Ray Bennett · Updated 2 October 2026 · 7 min read · Checked against the sources at the end

What Temperature to Set: Summer, Winter and Away

Short answer

The famous numbers, 78 in summer and 68 in winter, came from an energy campaign rather than from anything about comfort, and plenty of people are miserable at both. Here are honest ranges, what each degree is actually worth, and the one rule that is different for a heat pump.

Ask what temperature to set and you get two numbers back, every time. Seventy eight in summer, sixty eight in winter.

Those came from a government energy campaign decades ago. They are not wrong exactly, but they were chosen to save fuel rather than to make anybody comfortable, and a lot of people who try them are quietly unhappy and assume that is their own fault.

Before you start

What to carry: nothing, but a cheap thermometer in the room you actually sit in is worth having. Ten minutes.

Gas, electric or heat pump. For a gas or electric furnace and for ordinary air conditioning, everything here applies the same way. A heat pump follows one different rule and it has its own section further down, because getting it wrong there costs real money.

Measure before you argue. A thermostat reads the wall it is screwed to, not the sofa. It is very common for a room to sit three or four degrees away from what the display says: how to check what your thermostat is actually reading.

Two settings that are about safety rather than money. Never set the heat fully off in winter. Fifty five is the usual floor, and it is there because of pipes rather than comfort. A house left cold for a week while you are away is how people come home to a burst pipe: what freezes first, and why.

And cold and heat are genuinely dangerous to some people. For an older person, a small child or anybody unwell, a house below sixty in winter or above the low eighties in summer is a health problem, not a matter of toughening up. Those households should ignore the money and set what keeps them safe.

Pets stay in the same rules. A house left at ninety with an animal in it is not acceptable, however good the savings look.

The honest numbers

Ranges rather than single numbers, because comfort at a given temperature depends on humidity, on the sun and on what you are doing.

Check 1

Pick a range, then move one degree at a time

Summer, awake and at home. Seventy two to seventy eight. Most people settle around seventy four or seventy five, and the ones who are happy at seventy eight usually have low humidity or a ceiling fan.

Summer, asleep. Most people sleep better a little cooler, so the same as the day or a degree or two below, which is the opposite of what saving advice says.

Winter, awake and at home. Sixty eight to seventy two.

Winter, asleep. Sixty two to sixty six for most people, and this is the easiest saving in the whole house because you are under a duvet for all of it.

What a degree is worth. The usual rule of thumb is around three percent of the running cost of that system for each degree closer to the outdoor temperature. It is a rule of thumb and not a measurement of your house, but it is close enough to decide with.

Move one degree and live with it for three days. Comfort is not a number you work out, it is one you find, and jumping four degrees at once just makes everybody cross.

Humidity does more than temperature

Check 2

Fix the damp and the number stops mattering so much

Seventy eight at forty five percent humidity is comfortable. Seventy four at sixty five percent is not. That is one of the biggest reasons two houses disagree about what a good summer setting is.

So try the dry fixes before dropping the temperature. The fan on Auto rather than On, a longer run time, and a look at the drain are all free: why the fan setting changes how damp a house feels.

A ceiling fan is worth about four degrees. DOE says a fan lets you set the thermostat about 4°F higher with no loss in comfort. It does not cool a room at all, it moves air over skin, which feels the same and costs a fraction. Switch it off when the room is empty, because it is only doing anything when somebody is in it: which way a ceiling fan should turn.

In winter it is the other way round. A dry house feels colder than it is, and a lot of people run seventy two in January to chase a feeling that a little humidity would fix: how much humidity is safe when it is cold out.

Sun through a window beats the thermostat. Closing blinds on the sunny side in the afternoon is free and does more than a degree on the dial.

Away, asleep, and on holiday

Check 3

What to leave it on when nobody is there

Out for the day in summer. Eighty to eighty two. Not off, because a closed house in July climbs past a hundred and your system then spends the whole evening catching up.

Away for a week in summer. Eighty five is the usual ceiling. Above that, damp builds up, wood and instruments suffer, and mould gets going in a house with nobody opening a window.

Out for the day in winter. Sixty two to sixty five.

Away for a week in winter. Fifty five to sixty, and check what the forecast is doing before you leave. Fifty five is a pipe limit, not a comfort one.

Do not set back for less than about four hours. A short dip out and back achieves nothing and makes the system work in bursts.

And set it to come back before you do. A house takes an hour or more to recover, so a schedule that starts when you walk in leaves you cold for the first hour and saves nothing after that.

The setback argument, settled

For a furnace or an air conditioner a setback always wins. For a heat pump a deep one wakes up the electric heaters, and those cost two to three times as much to run.

Check 4

Which of the two rules applies to your system

The myth. That it costs more to warm the house back up than you saved by letting it cool, so you may as well leave it steady.

Why it is not true on a furnace or an air conditioner. A house loses heat in proportion to how different it is from outside. A cooler house in winter leaks less, every hour it sits there, and warming it back up only replaces what leaked. The saving is real and the recovery never eats it.

Why a heat pump is different. A heat pump heats gently and steadily. Ask it to climb several degrees quickly and the thermostat calls in the electric strip heaters to help, and those are the expensive way to heat a house.

So on a heat pump, keep the setback small enough that the strips stay off. DOE gives no number for it. The other answer is a thermostat with an adaptive or intelligent recovery setting, which starts early and climbs gently enough to leave the strips alone: how to tell when the expensive backup heat is running.

On a heat pump, never jump the dial to catch up. Pushing it up five degrees to warm the house faster is exactly the action that turns the strips on. Small steps, or leave it alone.

Questions people ask

Is 72 in summer wasteful?

It costs more than 76 and it is not a moral failing. If the house is comfortable at 76 with the humidity under control, you get the same feeling for less, and that is the useful way round to think about it.

Does turning the dial further make it cool faster?

No. DOE says a colder setting will not cool your home any faster. It only runs longer, so setting 65 to reach 74 quickly just means it overshoots and you have paid for the extra.

What about overnight in a bedroom that is always hot?

That is a balance problem rather than a setting problem, and turning the whole house down to fix one room is the expensive way: why upstairs and downstairs never agree.

Should I turn the air conditioning off completely when I go out?

Not in real heat. The house and everything in it soaks up heat all day, and the evening catch up usually costs more than the afternoon saved, quite apart from the damp.

My smart thermostat keeps changing it for me.

Most of them learn, and most of them can be told to stop. If it is doing something you did not ask for, look for the scheduling or the eco feature rather than assuming it is broken.

Everyone in the house wants something different.

Common, and it is usually not really about the number. Draughts, a sunny window, a cold floor and humidity all make the same room feel different to two people: where the cold air is actually coming from.

Sources: U.S. Department of Energy Energy Saver Guide (2017) (thermostat setback, heat pump setback, ceiling fans about 4°F) and the DOE Energy Saver "Thermostats" and "Programmable Thermostats" pages (68°F and 78°F, as much as 1% a degree for an 8 hour setback, setting back when the house is empty four hours or more, the reheating myth), and the American Red Cross "Frozen Pipes" (no lower than 55°F when away)