The bill is rising, the forecast looks stubborn, and you’re about to lock the door. Do you leave the heating on low, or trust the timers to do their job when you’re miles away?
The house feels like a living thing at that moment, quietly deciding how fast it will cool, how it will welcome you back later. You think about the last time you returned to a room that felt like a fridge, toeing off shoes and waiting for radiators to whisper into life, timing your comfort to the boiler’s mood. And you remember the other time you walked into a gentle, ready warmth and felt instantly human again, like someone had put the evening on fast-forward. Somewhere in that tension lives the right routine, the one that doesn’t bleed cash or comfort. The answer’s not what most of us were told.
What really keeps heat in when you’re away
Homes cool down in patterns, not in straight lines, and the biggest leaks rarely come from where you expect. The quick thieves are draughts around letterboxes, floorboards and sash frames, while the slow ones are big surfaces like external walls that quietly sip heat all day. That’s why a small “setback” temperature while you’re out often works better than turning the system off and letting rooms crash to cold.
In a typical British semi with decent loft insulation and double glazing, the room temperature might drop a couple of degrees over a few hours if it starts at 18–19°C. In a draughty terrace with bare floorboards, you might see a sharper slide. A friend measured it with a cheap sensor last January: kitchen down 3°C in four hours, bedroom down 1°C, hallway almost flat thanks to a closed door and a thick runner. Small habits changed that story the next week.
The logic is simple. Heating air from, say, 15°C back to 19°C asks more of your boiler than nudging 17°C to 19°C, and the fabric of the building—walls, floors, furniture—behaves like a big thermal battery. Keep that battery from going stone cold and your system doesn’t have to sprint every evening. **Heat only when you need it**, yes, but use a thermostat and a timer to keep the lows from getting too low.
Timers, thermostats and smart routines that work
Set your timer so the heating wakes up before you do and before you come home—30 to 45 minutes is a good starting window for most gas boilers. Aim for a setback of 16–17°C when the house is empty, then lift to 18–19°C for living time. If you’ve got TRVs on radiators, set bedrooms a notch lower and the room you use first a notch higher. Many smart thermostats can “pre-heat” so the house reaches your target exactly at 7:00, not 7:40.
We’ve all had that moment when we realise the thermostat lives above a radiator or in direct sun, which means it lies about the whole house. Move it to a hallway or a frequently used room, away from heat sources and draughts. Bleed radiators at the start of the season, keep big sofas off them, and check your boiler’s flow temperature: condensing models are happiest at lower flow, often around 55–60°C. Let’s be honest: nobody actually does that every day.
Think in rooms, not in house-wide absolutes. Keep doors closed to box in warmth, and let timers do quiet work while you’re out. Warmth is a habit, not a switch.
“People ask me if they should leave the heating on low all day,” says Jason, a heating engineer in Leeds. “For most modern homes, timed heat with a sensible setback wins. The exception is a very leaky house that loses heat as fast as you put it in—fix the leaks first.”
- Set a setback, not a standby. 16–17°C while you’re out keeps the fabric warm without running the boiler hard.
- Use geofencing on a smart thermostat so the heat nudges on as you head home, not at a fixed hour you might miss.
- Close doors, trap heat. Room-by-room control beats one big thermostat war.
- Lower boiler flow temperature on condensing boilers for extra efficiency and quieter radiators.
- Draft-proof the quick leaks: letterbox brush, keyhole cover, foam strips on gaps, a runner over bare boards.
Simple habits that quietly save heat
Thick curtains help, but only if they don’t fall over the radiator—tie-backs keep the heat in the room, not on the window. Blinds down at dusk create a little cushion of still air; daylight up again to stop condensation building. If you’ve got a hot water cylinder, put it on its own schedule and wrap it well. Your hallway will feel calmer and your boiler will spend less time in a sulk.
Radiator reflectors on external walls can nudge warmth back into the room. Not glamorous, but effective. Kitchen and bathroom extracts should run just long enough to clear steam, not drag heat out for an hour. **Lower the flow, raise the comfort** makes sense on cold weeks when a condensing boiler hums along rather than racing to high temperatures and shutting off again. A quiet system tends to be a frugal system.
Frost protection matters on bitter nights if you’re away longer. Most modern boilers have a frost stat, and pipe lagging in unheated spaces is cheap insurance. If you’re going away for a weekend, leave the heating on a 12–15°C guard and water on if the house is well insulated; if it isn’t, a deeper setback and thorough pipe lagging helps. Soyons honnêtes : personne ne fait vraiment ça tous les jours. Pick one small habit and keep it. Your house will notice.
| Key points | Detail | Reader Interest |
|---|---|---|
| Use a setback when you’re out | 16–17°C keeps the building’s thermal mass from going cold, so evenings heat faster | Comfort on arrival without all-day burn |
| Time the heat, don’t chase it | Pre-heat 30–45 minutes before return; geofencing can do it automatically | Warm welcome and lower stress |
| Fix quick leaks, guide the heat | Draught strips, door discipline, radiator clearance, lower boiler flow for condensing models | Small wins that feel big on cold nights |
FAQ :
- Should I leave the heating on low all day?For most homes, timed heating with a modest setback beats constant low heat. You avoid deep cool-downs without paying to heat an empty house.
- What thermostat setting works when I’m out?A setback around 16–17°C suits many UK homes. Older, leakier houses might need 17–18°C on icy days to prevent a big evening catch-up.
- Where should the thermostat go?Place it in a lived-in space or hallway, away from radiators, direct sun, kitchens, and exterior doors. Bad placement makes the whole system misread reality.
- Does lowering boiler flow temperature help?Yes for condensing boilers. A flow of 55–60°C often boosts efficiency and delivers gentler, steadier heat. Radiators may feel cooler to the touch, but rooms feel more even.
- What quick habits make the biggest difference?Close internal doors, clear radiators, drop blinds and curtains at dusk, draught-proof letterboxes and floor gaps, and use a pre-heat window on your timer or smart thermostat.
