Across the UK and Europe, many households wonder whether running radiators all day on a low setting is worthwhile. With gas and electricity bills rising, the practice can seem reassuring and even sensible. However, an industrial engineer specialising in household energy says the belief should be discarded.
The myth of “always on” heating
At first glance, the argument appears convincing: if a property is never allowed to cool, the boiler will supposedly “work less” and consume less energy. The message is frequently repeated on social media, while some landlords even pass the advice on to tenants.
From an energy perspective, keeping your heating constantly on at low temperature to save money is false, says industrial engineer Jorge Morales de Labra.
Jorge Morales de Labra, a Spanish industrial engineer who regularly discusses energy use, recently explained his reasoning on radio. His point is rooted in basic physics: a heating system uses energy for every minute it operates. The longer it remains running, the more energy it uses, regardless of a low thermostat setting.
He also says that, in most cases, it is cheaper to turn the heating fully off whenever you leave the house, including for a brief trip. Even if you pop out for a few minutes to buy bread, he maintains that switching the boiler off and then on again will generally use less energy than allowing it to idle in the background.
Why “low and constant” doesn’t add up
Heat loss never stops
Heat continually escapes from homes through walls, roofs, windows and small gaps around doors. The larger the difference between indoor and outdoor temperatures, the faster that loss occurs. Keeping a home at 20°C when it is 5°C outside therefore means heat is escaping throughout the day.
Maintaining 20°C requires the boiler or heat pump to keep replacing that lost warmth. When the heating is switched off, indoor temperatures can drop a little, narrowing the gap with the outdoor air and reducing heat losses while the system is inactive.
The moment the heating stops, heat loss slows. Less time running usually means less energy burned over the week or the month.
Short breaks still matter
It is commonly assumed that heating should only be turned off during lengthy periods away from home. Morales de Labra disputes this view. He says that even an absence of 20–30 minutes can lead to measurable savings, as the system is not operating and no fuel is being used during that time.
Modern boilers and heat pumps restart efficiently, without the same drawbacks associated with older equipment. In most homes with reasonable insulation, the “start-up cost” - the burst of energy used as the system starts again - is lower than the energy saved during a short period with the heating off.
Thermostats, not intuition
In practice, household heating systems are rarely as predictable as theoretical models suggest. Different rooms heat up at different rates, radiators may contain trapped air, and residents sometimes open windows. A programmable thermostat provides more reliable control than relying on instinct.
- Keep living spaces at a comfortable daytime range of roughly 19–21°C.
- Allow bedrooms and hallways to remain a little cooler.
- Reduce the temperature setting by several degrees overnight and when nobody is home.
- Set timed programmes that reflect your real daily schedule.
Energy experts regularly make the same point: raising the thermostat by each additional degree can increase consumption by approximately 6–8%. A seemingly minor adjustment can therefore add substantially to winter bills.
Practical ways to cut winter heating costs
Temperature, timing and behaviour
Morales de Labra argues that managing heating effectively is not about enduring cold conditions; it is about using energy only when and where it improves comfort.
The goal is not “spend less at all costs”, but use energy better and avoid waste that never improves comfort.
Most domestic energy bills are influenced by three main factors: temperature settings, hours of operation and the performance of the building itself.
| Action | Typical impact |
|---|---|
| Reduce thermostat by 1°C | About 6–8% less energy use |
| Turn heating off when away | Cuts runtime, lowers total fuel burned |
| Improve window and door sealing | Reduces drafts, slows constant heat loss |
| Use daily schedules | Heating only when the home is occupied |
Insulation and simple fixes at home
No heating approach performs particularly well in a property where warmth escapes from every direction. In poorly insulated flats, heat can disappear so quickly that the boiler cycles continuously, even at moderate settings. Although improving insulation can deliver lasting savings, the first measures do not always require expensive renovation.
Households can take action in several ways without carrying out building work:
- Fit adhesive sealing strips around windows and doors.
- Hang thick curtains and draw them at night to retain indoor warmth.
- Put rugs over cold floors to lessen the feeling of chill.
- Shut internal doors to keep warmth in the rooms that are actually in use.
By slowing heat loss, these measures allow the heating system to spend more time resting and operate in shorter bursts.
Using free solar heat wisely
Winter sunshine can still provide free heat, including in northern climates. South-facing windows can work like passive radiators if blinds and curtains are kept open through the day. Once the sun goes down, closing them promptly helps retain some of that warmth inside.
Think of curtains and blinds as a second, temporary layer of insulation you control daily at no extra cost.
In smaller living rooms especially, the difference between a home that receives solar gain all day and one kept behind closed blinds can amount to several degrees.
Rethinking common heating habits
Comfort versus habit
Many heating routines are driven more by a fear of feeling cold than by evidence. Some people keep radiators on “just in case”, while others heat unused rooms simply because “they have always done it that way”. Once energy prices increase, these patterns can become costly.
Energy engineers often suggest a straightforward exercise: walk around the home one evening and consider when each room needs heating and why. A spare bedroom, storage area or hallway may require much less warmth than a lounge or a child’s bedroom.
This assessment often results in smaller areas being heated, fewer hours of operation and reduced bills, with little noticeable effect on comfort.
When “always on” might feel tempting
There are limited situations in which near-continuous low-level heating may appear attractive: very old properties with thick stone walls, homes with serious damp problems, or households with people who have medical needs that make temperature fluctuations difficult. Even in these cases, engineers usually favour controlled setbacks over genuinely constant heating.
Rather than operating a boiler 24/7, a specialist may advise a smaller overnight setback, a moderate daytime temperature and focused improvements to the most exposed walls or windows. The same rule applies: reduce operating time and avoid unnecessarily large indoor-to-outdoor temperature differences when a room is not being used.
Looking ahead: smarter, not harder, heating
Smart thermostats and connected radiator valves provide an additional level of control. They can learn occupancy routines, identify open windows and manage temperatures room by room. For many households, such devices make it easier to move away from the “always on” myth, as heating is automatically reduced during periods when the home is empty.
For instance, a family could programme the home to remain at 17°C during working hours, increase to 20°C an hour before everyone returns and reduce again at bedtime. The boiler operates for less time, the house can still feel comfortable on arrival, and seasonal bills fall.
Anyone uncertain about how their own property responds can run a simple test over two cold weeks. Maintain the normal comfort level, but compare one week of constant low heating with another week using scheduled heating and small setbacks. Checking real usage on a smart meter often changes opinions more quickly than any technical explanation.
The discussion ultimately raises a wider issue: how to stay comfortable through colder months without wasting money and energy. According to engineers such as Jorge Morales de Labra, the solution is not to leave heating systems quietly running in the background, but to decide when warmth is genuinely needed - and reduce everything else.
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