Should You Leave Heating On All Day? Jorge Morales de Labra Explains

Across the UK and Europe, many families wonder whether leaving radiators on all day at a low setting is worthwhile. With gas and electricity costs rising, the practice can seem reassuring and even sensible. However, an industrial engineer specialising in household energy argues that the belief should be discarded.

The myth of “always on” heating

At first glance, the argument appears convincing: preventing a home from cooling should mean the boiler “works less” and the heating system uses less energy. The idea is repeated in social media discussions, while some landlords also advise tenants to follow it.

From an energy perspective, keeping your heating constantly on at low temperature to save money is false, says industrial engineer Jorge Morales de Labra.

Morales de Labra, a Spanish industrial engineer who frequently discusses energy use, recently explained his reasoning on the radio. His case comes down to basic physics: a heating system consumes energy for every minute that it operates. The longer it remains switched on, the more it uses, regardless of a low thermostat setting.

He also says it is generally cheaper to turn the heating fully off when leaving the house, including for a brief trip. Even if you only go out to buy bread for a few minutes, he maintains that switching the boiler off and on again will usually use less energy than allowing it to tick over in the background.

Why “low and constant” doesn’t add up

Heat loss never stops

Heat is continually lost from homes through walls, roofs, windows and small gaps around doors. The greater the difference between outdoor and indoor temperatures, the faster that loss becomes. Keeping a home at 20°C when it is 5°C outside therefore means warmth escapes throughout the day.

Maintaining 20°C all the time requires a boiler or heat pump to keep replacing that lost heat. Switching the heating off lets the indoor temperature drop a little, narrowing the gap with the outside air and reducing heat losses while the system is off.

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 widely assumed that switching the heating off is only worthwhile during long periods away. Morales de Labra disputes this view. Periods as short as 20–30 minutes can still deliver measurable savings, because the system is inactive 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 reasonably insulated homes, the “start-up cost” - the initial burst of energy when heating begins again - is lower than the energy saved during a short switch-off period.

Thermostats, not intuition

In practice, home heating systems seldom perform as smoothly as theory suggests. Different rooms heat up at different rates, radiators may contain trapped air, and residents sometimes open windows. A programmable thermostat manages these variables more effectively than relying on instinct.

• Keep living areas at a comfortable daytime setting of around 19–21°C.
• Allow bedrooms and hallways to remain a little cooler.
• Reduce the thermostat setting by several degrees overnight and whenever the property is empty.
• Set schedules so heating follows your real daily routine.

Energy experts regularly stress that each extra degree added to the thermostat may raise energy consumption by around 6–8%. Over an entire winter, that seemingly minor adjustment can add substantially to household bills.

Practical ways to cut winter heating costs

Temperature, timing and behaviour

Morales de Labra says effective heating control is not about enduring cold conditions; it is about using energy only where and when it improves comfort.

The goal is not “spend less at all costs”, but use energy better and avoid waste that never improves comfort.

Most household energy bills are influenced by three main factors: temperature, operating time 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 especially well in a property that loses warmth from every direction. In poorly insulated flats, heat can escape so quickly that a boiler cycles repeatedly even at moderate settings. Although improving insulation can bring lasting savings, the first steps can often be simple and inexpensive.

Households can make several improvements without carrying out renovation work:

• Apply adhesive sealing strips around windows and doors.
• Hang heavy curtains and draw them at night to retain warmth indoors.
• Put rugs on cold flooring to lessen the feeling of cold.
• Shut internal doors to concentrate heat in the rooms being used.

These measures reduce the rate of heat loss, allowing the heating system to stay off for longer and operate in shorter bursts.

Using free solar heat wisely

Winter sunshine can provide free heat, including in northern climates. South-facing windows can work as passive radiators when curtains and blinds are left open during daylight hours. Closing them promptly after sunset 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.

The difference between a home that benefits from solar gain all day and one kept behind closed blinds may be several degrees, particularly in smaller living rooms.

Rethinking common heating habits

Comfort versus habit

Many heating routines are driven by anxiety about cold weather rather than evidence. Some people keep radiators running “just in case”, while others heat unused spaces because “they have always done it that way”. When energy prices rise sharply, these habits become expensive.

Energy engineers often suggest a straightforward exercise: go around the home one evening and consider when each room needs heating and why. A spare bedroom, storage area or hallway may require far less warmth than a living room or a child’s bedroom.

This assessment commonly results in smaller heated areas, reduced running hours and cheaper bills, with little effect on comfort.

When “always on” might feel tempting

There are limited circumstances in which almost continuous low-level heating can appear attractive: very old properties with thick stone walls, homes affected by serious damp, or households where someone has a medical need that makes temperature changes difficult to tolerate. Even in these situations, engineers generally favour controlled setbacks over genuinely constant heating.

Rather than keeping a boiler operating 24/7, a specialist may recommend a less pronounced overnight setback, a moderate daytime temperature and focused improvements to the most exposed windows or walls. The underlying principle remains unchanged: reduce operating time and avoid large indoor-to-outdoor temperature differences when the space is not being used.

Looking ahead: smarter, not harder, heating

Smart thermostats and connected radiator valves provide an additional level of control. They can identify occupancy patterns, recognise open windows and regulate heating room by room. For many households, these devices offer an easy route away from the “always on” heating myth, automatically reducing heating while nobody is home.

For instance, a family could programme the property to remain at 17°C during working hours, increase to 20°C one hour before they arrive home, then fall again at bedtime. The boiler operates for less time, rooms are still 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 your usual comfort level, but compare one week of low constant heating with another week using timed heating and modest setbacks. Checking real usage on a smart meter often changes opinions more quickly than a technical explanation.

The discussion ultimately raises a wider issue: how to stay comfortable during 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 heat is genuinely needed - and reduce the rest.