The most energy-efficient winter temperature for a UK home is between 18°C and 21°C, with 18°C being the ideal setpoint for unoccupied rooms and 20°C for living areas, according to the Energy Saving Trust (Energy Saving Trust, 2026).
The right temperature depends on your household’s activity and health. For most adults, 18°C is safe and comfortable while awake and active, but older people or those with health conditions may need 20°C or slightly higher. The World Health Organisation recommends at least 18°C for healthy adults and 20°C for the elderly or those with respiratory issues. Dropping the thermostat by just 1°C can cut your heating bill by around 10% per year (Energy Saving Trust, 2026).
Set your living room to 20°C
For rooms you use most, such as the living room, 20°C balances comfort and cost. The average UK household spends around £1,200 per year on gas heating (Ofgem, 2026). Reducing your thermostat from 21°C to 20°C could save roughly £80–£100 annually. Use a programmable thermostat to heat only occupied rooms at specific times. Avoid turning the thermostat up higher than needed; the house will not warm up faster, and it wastes energy.
Keep bedrooms at 16°C to 18°C
Cooler bedrooms improve sleep quality and reduce heating costs. The NHS recommends a bedroom temperature of 16°C to 18°C for restful sleep (NHS, 2026). If you use a heated blanket or extra duvet, you can turn off radiators in unoccupied bedrooms entirely. For a three-bedroom house, turning off radiators in two unused bedrooms and keeping the doors closed can save around 5% on your heating bill, according to the Energy Saving Trust (Energy Saving Trust, 2026).
Never let your home drop below 12°C
To prevent damp and mould, maintain a minimum temperature of 12°C in unoccupied rooms. The UK Health Security Agency states that homes kept below 12°C for extended periods increase the risk of condensation and mould growth (UKHSA, 2026). If you go away for several days, set your thermostat to at least 12°C to protect the property. For occupied rooms, never go below 16°C if anyone in the household is over 65 or has a long-term health condition.
A worked example
A typical 1930s semi-detached house in Manchester heating to 20°C in living areas and 18°C elsewhere saves roughly £180 per year compared to keeping the whole home at 21°C. This home has 80m² of heated floor area, a modern condensing boiler, and average insulation. The household sets the programmable thermostat to 20°C in the living room from 7am to 10pm, 18°C in bedrooms, and 16°C overnight. According to the Energy Saving Trust, each 1°C reduction cuts heating bills by around 10%, meaning a drop from 21°C to 20°C saves approximately 10% of the £1,200 annual gas bill. With a smart thermostat costing £200 installed and 0% VAT until March 2027, the payback takes just over a year. Over 25 years, total savings reach £4,500 at current energy prices.
| Item | Figure |
|---|---|
| Upfront cost after grants | £200 |
| Yearly savings | £180 |
| Payback period | 1.1 years |
| 25-year lifetime savings | £4,500 |
What homeowners often get wrong
The most common mistake is turning the thermostat up higher to heat the house faster, which wastes energy and never speeds up warming. Here are three frequent errors and the correct approach to save money.
- Cranking the thermostat to 25°C for quick warmth A boiler or heat pump runs at the same output regardless of the thermostat setting, so the house warms up at the same speed. The result is overheating, wasted fuel, and a higher bill, roughly £120 extra per year for a 5°C overshoot.
- Heating empty rooms to the same temperature as living spaces Many UK homes heat bedrooms, hallways, and spare rooms to 20°C or higher. Dropping unoccupied rooms to 18°C saves about 10% of the total heating bill, or roughly £120 annually for a typical semi-detached house.
- Ignoring the boiler flow temperature setting Most condensing boilers are set to 70°C or higher, but reducing the flow temperature to 55°C for heating improves efficiency by up to 10%. This simple adjustment costs nothing and can save £60–£80 per year on gas bills.
Quick reference
- Lowering your thermostat by 1°C cuts heating bills by around 10%, saving the average UK household £80–£120 per year.
- The World Health Organisation recommends at least 18°C for healthy adults and 20°C for the elderly or those with health conditions.
- Setting bedrooms to 16°C–18°C improves sleep quality and reduces heating costs by approximately 5% compared to 20°C.
- A programmable or smart thermostat pays for itself within one to two years through reduced energy use.
- Turning the thermostat up higher does not heat your home faster and wastes roughly 5% of energy for every 1°C overshoot above your target temperature.
Frequently Asked Questions
18°C for unoccupied rooms and 20°C for living areas, per the Energy Saving Trust. Each degree lower saves roughly 10% on heating bills.
Set it to 18°C when you're active and 20°C in living spaces. The Energy Saving Trust confirms this balance cuts annual costs by £80–£100.
No, 18°C is safe for healthy adults according to the World Health Organization. Older or vulnerable people may need 20°C for comfort and health.
