The cheapest time to fix your heating is before you actually need it. Once the cold weather arrives and the boiler is running every day, a fault means an emergency call-out at peak rates, a chilly house and a long wait for an engineer. Spend an afternoon in September or October running through a short checklist and you head off most of that, while also shaving a useful chunk off the bills you are about to start paying. Most of the jobs below cost nothing and use tools you already own.
The short answer. Before winter, bleed your radiators, turn the boiler flow temperature down to around 60C, seal the obvious draughts and book a boiler service if it is overdue. Lowering the flow temperature alone can cut gas use by roughly 9% on a combi boiler, which on a typical heating bill is worth tens of pounds a year for a five minute job. Do the free jobs first, then decide whether any paid work is worth it.
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Start with the free jobs that make heat actually reach you
Before you spend a penny, make sure the heat your boiler produces is getting into the rooms. Two common faults quietly waste gas all winter, and both are free to fix.
The first is trapped air. Air collects at the top of radiators over the summer, so they run hot at the bottom and cold at the top, and the boiler runs longer to compensate. Turn the heating on for ten minutes, feel each radiator, and bleed any with cold tops. Our guide on how to bleed radiators walks through it with a radiator key and a cloth. While the system is on, check whether some radiators heat up much faster than others. If the far ones stay cool, the system may need balancing so flow is shared evenly.
The second is your boiler flow temperature, which is the temperature of the water the boiler sends to the radiators. Many boilers leave the factory set at 75C to 80C, which is hotter than a condensing boiler needs and stops it condensing efficiently. Turning it down to around 60C lets the boiler recover more heat from its own exhaust gases. Nesta's testing found this cuts gas use by roughly 9% on a typical combi boiler with no loss of comfort, because the radiators simply stay warm for longer rather than running scorching hot. See boiler flow temperature for how to find the dial. Note this is the flow temperature, not your room thermostat, which you set separately.
Seal the draughts before the wind gets cold
A draughty house loses warm air as fast as the boiler can make it, so sealing gaps is among the best-value autumn jobs. The Energy Saving Trust puts professional draught-proofing at around £45 a year in savings, and a DIY job costs far less than that to do.
Work through the obvious culprits on a windy day, when you can feel where the cold air comes in:
- Gaps around external doors, fixed with self-adhesive foam strip and a brush strip on the front door.
- Letterboxes and keyholes, with a simple flap or cover.
- An open, unused chimney, which can be blocked with a chimney draught excluder or balloon.
- Gaps around window frames and skirting boards, filled with strip or sealant.
The full method is in our draught-proofing guide. Keep deliberate ventilation in kitchens and bathrooms working, since sealing those completely traps moisture and causes condensation and mould. The aim is to stop the draughts you never wanted, not to seal the house airtight.
Book the paid jobs early, while you still have a choice
A few jobs need a professional or some outlay. Booking them in early autumn means you get a slot before the December rush and you are not paying emergency rates because the boiler died on the coldest night.
An annual boiler service is the main one. It keeps the boiler running efficiently, catches faults before they strand you, and is usually a condition of keeping any warranty valid. In 2026 a one-off service from a local Gas Safe engineer typically runs £70 to £140, with the average around £100 and London at the higher end. If your boiler has not been serviced in over a year, or it is making new noises, book it now rather than in January.
Other autumn jobs worth pricing up while you have time:
- Lagging your hot water cylinder and exposed pipes, which is cheap and stops heat leaking before it reaches the tap.
- Insulating outdoor and loft pipes against freezing, which prevents the burst-pipe disaster that no amount of bill-saving makes up for.
- Topping up thin loft insulation to the recommended depth, which holds heat in the rooms below.
- Fitting thermostatic radiator valves so you can turn bedrooms down without touching the rest of the house.
What each job is worth
The table below gives a rough sense of where your autumn time is best spent. Savings depend heavily on your house, your boiler and how you currently heat, so treat these as a guide to priority rather than a promise.
| Autumn job | Cost to you | Typical annual saving |
|---|---|---|
| Bleed radiators | Free | Recovers lost output, faster warm-up |
| Lower flow temperature to 60C | Free | About 9% of gas heating use on a combi |
| DIY draught-proofing | Under £30 | Around £45 (Energy Saving Trust) |
| Cylinder jacket and pipe lagging | Around £20 to £40 | Around £40 to £50 on water heating |
| Annual boiler service | £70 to £140 | Avoids costly winter breakdowns |
| Top up loft insulation | Varies | Up to around £350 if currently bare |
Gas at 7.97p per kWh, Ofgem cap October to December 2026. Saving figures are Energy Saving Trust and Nesta estimates for a typical gas-heated home and will differ for your property.
The pattern is clear: the free jobs at the top deliver real savings for an afternoon's work, so do those first. The paid jobs lower down are more about avoiding disasters and chipping away at heat loss, and are worth doing in order of how draughty or cold your home already feels.
Tune the controls so you are not heating an empty house
With the system healthy, the last autumn job is making sure it only runs when and where you need it. Most homes waste heat by running the boiler on a fixed schedule that no longer matches the household.
Set your room thermostat to a comfortable level rather than a high one. The usual advice is somewhere between 18C and 21C, and every degree you turn it down saves roughly a few percent on heating. Our guide on what temperature to set your thermostat goes into the trade-offs. Then check your timer matches your actual routine, so the heating is not warming the house for hours after everyone has left or before anyone is up.
If you have thermostatic radiator valves, turn down the rooms you barely use rather than closing them off entirely, which keeps a little background warmth and helps avoid damp. A smart thermostat can automate a lot of this if you are upgrading, though it is not essential. The free win is simply matching the timer to your week before the cold sets in.
The bottom line
Getting your heating ready for winter is mostly a free afternoon, not a big spend. Bleed the radiators, drop the boiler flow temperature to around 60C, seal the draughts you can feel and match the timer to your routine, and you will go into winter using noticeably less gas than the house used last year. Then book the boiler service and any lagging before the December rush, so a cold snap finds you ready rather than waiting on an engineer.
Once these are done, run through our wider winter energy checklist to cover the rest of the home, pick off the cheapest fixes in quick wins under a tenner, and if you want to understand the running costs behind all of it, the heating and electricity hubs pull the numbers together.