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Quick answer
Yes. Turning a room thermostat down by one degree reduces the temperature difference between inside and outside, which reduces heat loss and the gas the boiler burns to replace it. The saving is often quoted at up to around 10% of heating energy, though the real figure depends on your house, how warm you kept it before and how your controls are set up. It works best when the thermostat is in the right place and the rest of the system is controlled properly. It is not advice for everyone: older people, babies and anyone with health conditions need a warm home.
Key takeaways
- A lower set temperature means less heat lost through walls, windows and roof, so less gas used.
- Savings are often quoted at up to around 10% of heating energy for a one degree drop, but vary by home.
- The thermostat must be in a sensible place, away from radiators, sunlight and draughts, for this to work.
- Turning the thermostat down is different from turning the boiler’s flow temperature down; both matter.
- UK health guidance recommends at least 18°C for most people in winter, and warmer for vulnerable households.
Why one degree makes a difference
A house loses heat in proportion to the difference between the inside and outside temperature. On a 5°C day, a home kept at 21°C has a 16 degree difference; at 20°C that becomes 15 degrees. That one degree is a meaningful share of the total heat loss, so the boiler burns less gas replacing it. The colder the weather and the leakier the house, the bigger the absolute saving.
What the saving is worth this winter
With the capped gas unit rate at 7.97p per kWh from October 2026, every kWh saved is worth a little under 8p. How many kWh you save depends on your heating demand. A small, well-insulated flat will save less in pounds than a draughty four-bedroom semi. The percentage is the useful figure: if heating is most of your gas bill, a one degree reduction is one of the cheapest changes you can make.
Thermostat vs flow temperature
People often confuse the room thermostat with the dial on the boiler. The room thermostat decides when the house is warm enough. The boiler’s flow temperature decides how hot the water sent to the radiators is. Lowering the flow temperature can let a condensing boiler work more efficiently; our guide to boiler flow temperature settings explains how. Turning the room thermostat down reduces how much heat the house needs. Doing both is sensible, within comfort limits.
Make sure the thermostat is reading correctly
A thermostat in a hallway next to a radiator, in direct sunlight, or above a lamp will read warmer than the living space and switch the heating off early. One on a cold external wall will keep the heating running too long. See where to put a room thermostat for placement tips. Pairing the thermostat with properly set TRVs gives you control room by room; read thermostat and TRV settings for winter.
Who should not go too low
UK Health Security Agency guidance recommends heating the rooms you use to at least 18°C in winter, and older people and those with health conditions may need it warmer. Cold homes are linked to worse respiratory and cardiovascular health. If you are caring for someone vulnerable, prioritise warmth and look for savings elsewhere, such as draught proofing and servicing.
Book with Gasmaster
Want your heating controls set up properly for winter? Gasmaster Plumbing & Heating, Gas Safe registered (220932), services boilers and heating systems across Stoke-on-Trent, Newcastle-under-Lyme and Biddulph. Book through our boiler service booking page.
Frequently asked questions
Is it better to turn the heating off or down?
For most homes, using a timer so the heating is off while you are out, plus a sensible thermostat setting, works better than leaving it on high. Our post on leaving the heating on low all day looks at when the alternative makes sense.
What temperature should I set my thermostat to?
Many households find 18 to 21°C comfortable. See what temperature your home should be in winter for more detail.
Will turning the thermostat down damage my boiler?
No. The boiler simply runs less often or at lower output.
Does this work with smart thermostats?
Yes. Smart thermostats make it easier to set different temperatures for different times, but the principle is the same.
Sources
- Energy Saving Trust, heating and thermostat guidance (energysavingtrust.org.uk)
- UK Health Security Agency, cold weather and health guidance (gov.uk)
- Ofgem, October to December 2026 price cap (ofgem.gov.uk)
Related services
Abdul runs Gasmaster Plumbing & Heating and has worked on boilers, heating and gas appliances across Stoke-on-Trent since 2005. He is Gas Safe registered (reg. 220932), and these articles come from his day to day work in homes and businesses across Staffordshire, Cheshire and Derbyshire.
