10 Ways to Cut Your Gas Boiler
Running Costs in 2026
The average UK home can save £200 to £400 per year on gas with these changes. Most cost nothing.
Updated April 2026
Lower boiler flow temperature to 60C
Cost
Free
Annual saving
£60 - £100/year
Payback period
Instant
Most combi boilers ship with a flow temperature of 75-80C. Dropping to 60C lets the boiler condense more efficiently, saving 6-8% on gas. You will not notice the difference in comfort. This is the single best free change you can make.
Drop thermostat by 1C
Cost
Free
Annual saving
£50 - £80/year
Payback period
Instant
Reducing your room thermostat from 21C to 20C cuts gas usage by roughly 10%. Most people cannot tell the difference. If you currently run at 22C or above, dropping by 1-2C can save over £100 per year.
Install TRVs on every radiator
Cost
£150 - £300
Annual saving
£75 - £150/year
Payback period
1-2 years
Thermostatic radiator valves let you control the temperature in each room independently. Turn bedrooms to 2, living areas to 3-4, and empty rooms to 1 or off. Stops you heating rooms nobody uses.
Get a smart thermostat
Cost
£150 - £250
Annual saving
£100 - £200/year
Payback period
1-2 years
Devices like Hive, Nest, or Tado learn your schedule and stop heating an empty house. They also provide usage data that helps you spot waste. The Nest Learning Thermostat is the most popular UK choice.
Bleed your radiators
Cost
Free
Annual saving
£20 - £50/year
Payback period
Instant
Air trapped in radiators creates cold spots and forces the boiler to work harder. If a radiator is warm at the bottom but cold at the top, it needs bleeding. Use a radiator key, turn off the heating, open the bleed valve until water appears. Takes 10 minutes.
Add loft insulation to 270mm
Cost
£300 - £500
Annual saving
£150 - £200/year
Payback period
2-3 years
A quarter of your home's heat is lost through the roof. Government-recommended insulation depth is 270mm. If your loft insulation is thin (under 100mm) or patchy, topping it up is one of the most cost-effective improvements available.
Cavity wall insulation
Cost
£400 - £800
Annual saving
£100 - £150/year
Payback period
3-5 years
If your home was built between the 1920s and 1990s, it likely has cavity walls that can be insulated. A professional drills small holes in the outer wall and injects insulation material. The holes are barely visible when filled.
Draught-proof doors and windows
Cost
£50 - £200
Annual saving
£40 - £80/year
Payback period
1-3 years
Self-adhesive foam strips for doors and windows cost under £20 from a DIY store. Chimney balloons (£10-20) stop heat escaping up unused chimneys. Keyhole covers and letterbox brushes help too. Small, cheap changes with a noticeable impact.
Upgrade to a condensing boiler
Cost
£1,800 - £3,500
Annual saving
£200 - £400/year
Payback period
5-10 years
If your boiler is over 15 years old and rated G or F for efficiency (60-70%), replacing it with a modern 92% efficient condensing boiler can cut your gas bill by 25-35%. This is the biggest single saving but requires upfront investment.
Annual boiler service
Cost
£80 - £120
Annual saving
Prevents £200+ efficiency loss
Payback period
Under 1 year
A boiler that has not been serviced for 3 years can lose 5-15% efficiency. That is £50-150 per year in wasted gas. A service also keeps your warranty valid and catches safety issues early. Book in August or September before the rush.
Total Potential Savings
Free measures only
£130 - £230/yr
Flow temp, thermostat, bleeding
With insulation and TRVs
£400 - £600/yr
All above plus insulation measures
With new boiler
£500 - £800/yr
If replacing a 15+ year old boiler
Frequently Asked Questions
What temperature should I set my boiler to?
For a combi boiler, set the flow temperature to 60C for the best balance of comfort and efficiency. The room thermostat should be at 19-21C. For system and conventional boilers, the cylinder thermostat should be at 60C and the boiler flow temperature can stay at 65-70C.
Do smart thermostats actually save money?
Yes, typically £100 to £200 per year for a household that was previously using a basic timer. The biggest savings come from automatic 'away' detection and learning your routine. If you already manage your heating carefully, savings may be smaller (£50-100).
Is it cheaper to leave heating on low all day?
No. Keeping heating on all day wastes energy by heating the house when nobody is there. It is cheaper to heat the house when you need it and turn it off when you do not. A smart thermostat automates this perfectly.