Heating Costs: Why Turning the Heating Down Too Far Can Backfire

Across Europe and the UK, countless households think they have found the answer to lower heating bills: turn radiators right down, or switch them off altogether, whenever the property is empty. The idea seems impossible to dispute. However, heating specialists warn that this apparently sensible tactic can have the opposite effect, making homes colder, increasing costs and placing extra pressure on heating systems.

The big mistake: turning everything down too far

As soon as freezing weather arrives, concerns about energy costs grow. Many people leave for work and drastically reduce the thermostat setting. When going out for a day or weekend, they turn off the heating entirely, assuming that every degree not used represents money saved.

The principle appears straightforward: if nobody is at home, there is no reason to heat it. Yet the way buildings retain and lose heat suggests otherwise. A home allowed to become excessively cold is not merely uncomfortable on your return; it effectively becomes a thermal sponge that needs warming throughout.

Slamming the heating right down can turn a day out into a marathon reheat that burns through more gas or electricity than you saved.

Walls, floors, ceilings, furnishings and even carpets retain warmth. If they are allowed to cool too far, a boiler, heat pump or electric radiators need to work intensely to heat the whole building again rather than simply warming the air. This sharp rise in energy use can frequently wipe out, or even exceed, the limited savings made while the home was empty.

Why experts favour small drops, not brutal cuts

Heating professionals now offer a simple rule of thumb: reduce the temperature while you are out for the day, but avoid a major reduction.

For short absences, specialists generally recommend cutting the set temperature by only 2–3°C, not shutting the heating down.

For a home normally kept at 20°C when occupied, lowering the setting to 17–18°C during the working day will generally suffice. This modest reduction offers several advantages:

• the property loses heat more gradually
• walls and furniture remain slightly warm, allowing quicker reheating
• the heating system does not need to run at full output for extended periods
• condensation and the unpleasant sensation of a damp cold home are reduced when you return

This measured strategy is very different from the all-or-nothing approach that creates repeated daily temperature shocks. Keeping temperatures within a smaller range reduces the demand placed on a boiler or heat pump while delivering steadier comfort.

What really happens when your home gets too cold

The belief that switching heating off always saves money overlooks how a building responds to cold. Once a living room temperature falls too low, three disadvantages begin to work against you:

1. Heavy structures act like ice blocks

Brick, concrete and stone have substantial thermal mass. Once cold, they act like enormous cold batteries. On returning home and raising the thermostat sharply, the heating system must supply warmth for hours to heat the building structure as well as the air around you.

2. Condensation and damp creep in

Moisture in the air collects on cold surfaces. You may then notice misted windows, clammy walls and a faintly musty odour. In time, that added moisture can promote mould and cause damage to paintwork or plaster.

3. You overcompensate in discomfort

A very cold house often makes people set the thermostat above their normal temperature “just to catch up”. They might turn on radiators in unoccupied rooms or keep the heating running at high levels well into the night. These responses create an additional source of waste.

A home that never drops too far below its comfort temperature is easier, cheaper and healthier to heat than one that swings from chilly to roasting every day.

The thermostat trick that quietly does the job

Heating experts repeatedly recommend the same solution: an uncomplicated programmable thermostat or smart heating control. It need not be sophisticated or costly to repay its price quickly.

A basic programmable thermostat can:

• reduce the temperature by 2–3°C during working hours
• restore the heating shortly before you get home
• stop rooms falling below roughly 16°C during normal absences
• use “frost protection” mode only when you are away for longer periods

Automation of this kind removes the problem of forgetting. It prevents heating from running unnecessarily all day, while also ensuring you do not return to a freezing living room and turn every control to maximum in frustration.

How far can you drop the temperature safely?

Experts normally separate absences into different categories and suggest approximate target temperatures:

Situation	Recommended indoor temperature	Reason
Typical workday absence (8–10 hours)	17–18°C	Lowers consumption while allowing rapid, efficient reheating
Short absence (evening out)	18–19°C	A slight reduction with no noticeable loss of comfort on return
Weekend away (2–3 days)	16–17°C	Reduces damp risk and safeguards the building fabric
Holiday of a week or more	12–14°C or frost‑protection setting	Helps prevent frozen pipes and mould while reducing costs

The advice from heating engineers is straightforward: for everyday absences, choose moderation instead of switching the heating off completely. Significant reductions are appropriate only for extended trips and, in cold climates, temperatures should still not fall below frost-protection levels.

Comfort, health and the “feels like” factor

There is also a human consideration. Comfort is determined by more than the thermostat reading alone. Humidity, air movement and radiant temperature - the warmth of nearby surfaces - all play a part.

People often feel cold in a 20°C room if walls and windows are chilly, yet feel fine at 18°C when surfaces stay warm and dry.

Preventing walls and furniture from cooling deeply increases radiant temperature and makes it less tempting to warm the air to 21–22°C. Over an entire winter, this small change can reduce a bill by several percent.

Real-life scenarios: where the “radical drop” goes wrong

Take a straightforward example. Household A leaves at 8am, lowers the heating from 20°C to 5°C, and returns at 6pm. By then, the home has cooled to close to the outdoor temperature. The boiler must then run almost constantly for hours to bring the building back to a comfortable level before bedtime.

Household B leaves at the same time but uses a programmable thermostat to reduce the setting from 20°C to 17°C, before increasing it to 20°C again from 5.15pm. Their boiler operates gently at a lower output over a longer timeframe, rather than facing an enormous surge in demand.

On arriving home, Household A feels cold and often raises the thermostat to 22°C “just for a bit”. Household B returns to a comfortable enough home and seldom needs to adjust the controls. Across a heating season, this distinction becomes significant.

Key terms that help you make sense of your bill

Two concepts appear regularly in professional advice:

• Thermal inertia: a building’s resistance to temperature change. Dense materials such as stone and concrete have high thermal inertia, so they take a long time to cool and warm. Properties with these materials benefit more from gentle, continuous heating.
• Setback temperature: the modestly reduced temperature maintained while you are away or asleep. An appropriate setback prevents both unnecessary energy use and excessive cooling.

Understanding these concepts makes it easier to recognise the flaw in thinking, “I’ll just turn it right down and save a fortune”. In most modern homes, carefully managed setbacks rather than dramatic switch-offs provide the strongest balance of comfort and cost.

Households that pair moderate setbacks with good insulation and a simple programmable thermostat can often cut their heating bill by several percent without experiencing a meaningful loss of comfort. Combining this with habits such as shutting curtains or shutters at night, sealing draughts and heating only occupied rooms can create a substantial combined effect over a single winter.