Many people set their thermostat wrong at night: heating engineers reveal the simple setting that saves hundreds each winter

Amelia Foster • January 22, 2026 11:19

The hallway was already cooling when he arrived, that damp, creeping chill you only notice once the boiler stops humming. My neighbour apologised for the mess, pointed vaguely at the thermostat and said what millions quietly think: “We just whack it on in the evening and turn it off before bed. That’s the cheapest, isn’t it?”

The engineer didn’t lecture. He pressed two buttons, nudged the temperature down a notch, and tapped a tiny icon most people never use: a moon with the word “ECO” beside it. The house would now drop a few degrees at night, then wake up warm on schedule. No more 5am shivers. No more 90‑minute boiler marathons trying to heat stone‑cold walls.

He scribbled the numbers on a sticky note – “20°C day, 16°C night, 14°C if you’re away” – and left the old “ON / OFF” habit behind with the tea mugs. The only visible change was the boiler working in shorter, calmer bursts instead of frantic sprints.

“Your house should cruise through the night, not keep doing emergency take‑offs at dawn,” he said on his way out.

Across a winter, that quiet tweak is the difference between paying to heat the whole night as if you were hosting a party, and paying just enough to keep the cold outside. It feels minor. On many UK bills, it adds up to hundreds of pounds.

The tiny setting that makes your heating act smart

Most modern thermostats and smart controls have a feature called a setback or night setting. Instead of running the heating at full daytime temperature or turning it completely off, the thermostat lets the house cool by a few degrees overnight – and then gently brings it back up before you get out of bed.

Heating engineers love this for two simple reasons:

It stops your boiler or heat pump from fighting a huge temperature drop each morning.
It stops you wasting money keeping rooms at 20–21°C while everyone is under a duvet.

The sweet spot in most reasonably insulated UK homes looks like this:

Day / evening (when you’re home and active): around 19–21°C in lived‑in rooms.
Night (asleep): drop by 3–5°C, so typically 15–17°C.
Away for work or a weekend: around 12–15°C, to prevent damp and frozen pipes without heating an empty house.

The “simple setting” that saves money isn’t a magic number; it’s using that automatic night‑time drop instead of treating the thermostat like a big on/off switch. You let the controls do the pacing so the boiler doesn’t have to sprint.

Why the night‑time setting matters more than you think

Heat in a house behaves like money in a leaky bucket. Warm air slips through walls, windows, roofs and floors. The bigger the temperature difference between indoors and outdoors, the faster it leaks.

Two things follow from that:

Keeping a house at full daytime temperature all night is like leaving the bucket under a running tap. You are constantly topping up heat that no one is awake to enjoy.
Letting the house plunge to near‑outdoor temperatures is a false economy. In the morning, the system has to run flat out to warm not just the air, but cold walls, floors and furniture.

A modest setback avoids both extremes. You still reduce heat loss – a house at 16°C leaks less energy than one at 20°C – but you never let the structure get so cold that re‑heating becomes a brutal, expensive catch‑up.

Modern condensing boilers and heat pumps are happiest ticking along steadily at moderate flow temperatures. A properly set night schedule lets them do just that:

fewer on/off cycles,
fewer noisy early‑morning blasts,
better efficiency while they run.

How to set your thermostat at night (step by step)

You do not need a smart home system for this. A basic programmable thermostat or timer is enough.

Find the programme or schedule button
Look for “PROG”, “SCHEDULE”, “AUTO”, a clock symbol, or a moon icon. If you only ever use “ON” and “OFF”, this is the bit you’ve been ignoring.
Set your daytime comfort temperature
- Choose 19–21°C for the main living period (for most households, something like 06:30–09:00 and 16:30–22:30).
- Older people, very young children, or anyone with health conditions may need the higher end of that range.
Add a night‑time setback block
- For the hours you’re normally in bed, programme 15–17°C.
- If you like a brisk bedroom, aim lower in the bedroom but keep the house as a whole above 14°C to guard against damp and pipe risks in cold snaps.
Tell the heating to wake up before you do
- Programme the morning temperature to rise 30–60 minutes before you get up, not at the same time.
- The colder and more solid your house (thick walls, big radiators), the earlier you start the warm‑up.
Use an “away” or “holiday” setting if you have one
- Set 12–15°C for longer absences.
- This keeps the building dry and the pipework protected without paying for empty rooms to feel cosy.
Fine‑tune over a few nights
- If you wake up too cold, raise the setback by 1°C.
- If you feel fine but bills are painful, lower it by 1°C and see how the house responds.

Think of the thermostat as a cruise‑control, not an accelerator pedal. Once you’ve set the route, stop fiddling; let it do the work.

Typical night‑time settings by home type

Every building leaks heat differently. Use this as a starting guide, then adjust to comfort and health needs.

Home type	Suggested night setting	Notes
New‑build / well‑insulated flat	15–16°C	Holds heat well; can usually cope with a bigger setback.
1930s semi with double glazing	16–17°C	Decent compromise between comfort and savings.
Older, draughty terrace or stone cottage	17–18°C	Loses heat quickly; use a gentler setback to avoid icy mornings.

If you have a heat pump, many installers recommend an even smaller setback (2–3°C), because pumps like very steady operation. In that case, think 20°C day, 17–18°C night, and let the system run low and long.

Common mistakes that quietly burn money

Engineers tend to see the same patterns from house to house. Most are easy to fix once you know they exist.

Leaving the thermostat at one fixed temperature, 24/7
Comfortable, yes; but you are heating bedrooms and hallways to daytime levels all night. A 3–4°C setback can trim 10–15% off space‑heating use in many homes.
Turning the heating fully off at night in a cold, solid house
The morning warm‑up then takes ages and runs at full blast. In older properties this can cost more than a controlled setback, and can encourage condensation and mould.
Cranking the thermostat up to “speed up” warming
A thermostat is not a throttle. Setting it to 25°C does not heat you to 20°C faster; it just overshoots and wastes energy if you forget to turn it down.
Closing TRVs (radiator valves) in the wrong places
Shutting off radiators in hallways where the main thermostat sits can trick the system into thinking the whole house is warm, leaving bedrooms chilly and the boiler cycling oddly.
Ignoring unused rooms altogether
Letting rarely used rooms fall to near‑outdoor temperatures invites damp. Keep them at around 12–14°C with doors open so the house heats more evenly.

Small corrections in these habits often deliver more savings than buying new gadgets. The “simple setting” works best when the rest of the system isn’t fighting against it.

What changes when night setback becomes a habit

After a fortnight of running a proper night schedule, most people notice three things.

First, mornings stop feeling brutal. The house is cooler at 3am, but not arctic at 7am. You step onto floors that feel like they belong to a home, not a garage.

Second, you touch the thermostat far less. Instead of late‑night dashes to turn things off and early‑morning scrambles to blast the heating, the system glides between states on its own. Fewer wild swings in temperature, fewer “Did you turn it off?” arguments.

Third, the boiler or heat pump sounds calmer. It cycles less, runs at lower flames or fan speeds, and tends to last longer when it’s not being asked to go from stone‑cold to sauna every day.

The bills don’t drop by half overnight. Yet over a whole winter, shaving 10–20% off gas or electricity use – simply by using a setting you already own – is not unusual. It’s not a new boiler. It’s not underfloor heating. It’s two or three degrees and a moon icon.

FAQ:

Is it cheaper to leave the heating on low all the time?
In most UK homes, no. It is usually cheaper to set sensible schedules with a night‑time setback, so you only heat when needed and let the house cool a little while you sleep or are out.

What night temperature is too low?
Below about 12–13°C indoors, you increase the risk of condensation, damp and pipe problems in cold weather. Vulnerable people may also be at risk below 18°C, so always balance savings with health and safety.

Does this advice change for heat pumps?
Slightly. Heat pumps prefer very steady running, so use a smaller setback (2–3°C) rather than big drops. Still, having a night‑time reduction is usually more efficient than holding full daytime comfort all night.

What if my thermostat is very old and has no schedule?
A simple programmable room thermostat often costs less than a month or two of winter fuel and can pay for itself quickly. If you rent, it is worth asking your landlord to fit one as part of basic efficiency upgrades.

Will turning radiators off in unused rooms save more than a setback?
It can help, but do it carefully. Keep some background heat (12–14°C) and doors slightly open so the house warms evenly and damp cannot build up in cold corners. A good setback plus sensible radiator use beats either trick on its own.