How fast does draught-proofing pay for itself?
Usually within a year or so if you do it yourself. Sealing the windows and outside door of a semi-detached house with a £49 DIY kit saves about £58 a year on gas at the October 2026 price cap, so it pays back in about 10 months. In a mid-floor flat it takes about 15 months.
Use the calculator to pick your home type and the draughts you still need to fix. It starts at the price cap rates of 7.97p per kWh for gas and 26.32p for electricity (1 October to 31 December 2026), and you can change any rate or price to match your own.
Work out your payback
Pick your home, tick the draughts you still need to fix, and change any price to match what you pay. Everything updates as you type.
What do you need to fix?
Example: D-Profile Foam Weather Strip (10m) (about £5–£8 on Amazon UK)
Example: Stormguard Acoustic Silent Seal (6m) (about £8–£12 on Amazon UK)
Example: Stormguard Aluminium Brush Bottom Door Seal (about £6–£10 on Amazon UK)
Example: STORMGUARD White Letterbox Cover Draught Excluder with Brush (about £5–£8 on Amazon UK)
Example: Chimney Balloon Draught Excluder (Medium) (about £15–£20 on Amazon UK)
Example: D-Profile Foam Weather Strip (10m) (about £5–£8 on Amazon UK)
| Job | Cost | Yearly saving | Payback |
|---|---|---|---|
| Windows and outside doors | £49.00 | £58.13 | 10 months |
The windows and doors saving is for sealing every window and outside door in a typical semi-detached house, so tick everything you still need to fix. That saving is 729 kWh a year, about £4.84 a month averaged over a year, though most of it comes in winter. Standing charges are left out.
Paying someone instead? The Energy Saving Trust puts professional draught proofing of windows and doors at around £250 for a whole house. At your rate that pays back in 52 months (about 4.3 years).
Draught-proofing payback by home type
Payback for the same £49 DIY kit (two rolls of foam strip, a frame seal and brush strip for one outside door, a letterbox cover and a keyhole cover), with gas heating at 7.97p per kWh.
| Home | Energy saved a year | Yearly saving | Payback |
|---|---|---|---|
| Detached house (about 104 m²) | 773 kWh | £61.58 | 10 months |
| Semi-detached house (about 89 m²) | 729 kWh | £58.13 | 10 months |
| Mid-terrace house (about 80 m²) | 685 kWh | £54.60 | 11 months |
| Bungalow (about 67 m²) | 406 kWh | £32.38 | 18 months |
| Mid-floor flat (about 61 m²) | 490 kWh | £39.02 | 15 months |
| Unused open chimney, any home (£20 chimney balloon) | 692 kWh | £55.18 | 4 months |
| Semi-detached, professional job (around £250) | 729 kWh | £58.13 | 52 months (about 4.3 years) |
Your home will differ. A draughty older home can save more, and one that is already well sealed will save less. Prices checked October 2026.
What each DIY fix costs
| Fix | Typical cost | Where the price comes from |
|---|---|---|
| Foam strip round windows that openExample: D-Profile Foam Weather Strip (10m) | £8 per 10m roll | Top of the £5 to £8 Amazon UK price band for a 10m roll |
| Seal round the frame of an outside doorExample: Stormguard Acoustic Silent Seal (6m) | £12 per door | Top of the £8 to £12 Amazon UK price band for a 6m seal |
| Brush strip along the bottom of an outside doorExample: Stormguard Aluminium Brush Bottom Door Seal | £10 per door | Top of the £6 to £10 Amazon UK price band. Which? says from about £6 |
| Letterbox cover with brushesExample: STORMGUARD White Letterbox Cover Draught Excluder with Brush | £8 per letterbox | Top of the £5 to £8 Amazon UK price band. Which? says under £10 |
| Keyhole cover | £3 per keyhole | Which? says a keyhole cover costs about £3 |
| Chimney balloon for an unused open fireplaceExample: Chimney Balloon Draught Excluder (Medium) | £20 per chimney | Top of the £15 to £20 Amazon UK price band |
| Foam strip round the loft hatchExample: D-Profile Foam Weather Strip (10m) | £8 per 10m roll | One 10m foam roll, top of the £5 to £8 Amazon UK price band |
| Filler for gaps in floorboards and skirting | Your own price | No typical price published, so type in what you pay |
We have not tested these products ourselves. Price bands come from our own Amazon UK checks in September 2026, so check the live price before you buy. Not sure which one suits your door? Our draught excluders guide and letterbox guide compare the options.
How it's worked out
Windows and outside doors. The energy saved for each home type comes from government modelling of sealing every window and outside door, published by the Department of Energy and Climate Change for the Green Deal. We take 15% off, as the Green Deal did, to allow for real homes doing less well than the model. Then we price that energy at today's rate. The Green Deal has closed and that document was withdrawn in 2025, so we only use its energy figures, not its old prices.
Cross-check. The Energy Saving Trust says draught proofing windows, floors and doors could save around £55 a year in Great Britain. It bases that on gas at 6.5p per kWh, which works out at about 846 kWh, or about £67 at today's cap. That is close to our figures.
Chimney. The Energy Saving Trust says draught proofing an unused open chimney could save around £45 a year in Great Britain. At its 6.5p gas price that is about 692 kWh, which we price at your rate.
Payback is the cost divided by the yearly saving, times 12. It is a simple guide. It ignores future price changes, and most of the saving comes in the colder months. Standing charges are left out because draught-proofing does not change them.
Before you start
- Never block air bricks, trickle vents, wall vents, extractor fans or flues.
- Leave kitchen and bathroom ventilation alone, as these rooms need fresh air to stop damp.
- Do not seal under internal doors. The Energy Saving Trust says that gap helps air move round your home.
- Take a chimney balloon out before you light a fire.
- Sash windows and older homes can be tricky, so a professional may be worth it.
Common questions
How long does draught-proofing take to pay for itself?
Usually within a year or two if you do it yourself. Sealing the windows and outside door of a semi-detached house with a £49 DIY kit saves about £58 a year on gas at the price cap, so it pays back in about 10 months. A chimney balloon in an unused fireplace can pay back in about 4 months.
How much does draught-proofing save a year?
The Energy Saving Trust says draught proofing windows, floors and doors could save around £55 a year in Great Britain, plus around £45 a year for an unused open chimney. At the October 2026 gas price cap of 7.97p per kWh, our figures for windows and outside doors run from about £32 a year for a bungalow to about £62 for a detached house.
How much does it cost to draught-proof a house yourself?
Not much. Which? says a door brush strip starts from about £6, a letterbox cover is under £10 and a keyhole cover is about £3. Our example kit of two rolls of foam strip, an outside door seal and brush, a letterbox cover and a keyhole cover comes to £49. Paying a professional to do the whole house costs around £250, according to the Energy Saving Trust.
Is it worth paying a professional to draught-proof?
It can be, especially for sash windows or an older home. At around £250, a professional job on a semi-detached house would take about 52 months (about 4.3 years) to pay back at the gas price cap. The Energy Saving Trust says a professional is likely to save more energy because they know which materials to use where.
Does the calculator work if I have electric heating?
Yes. Choose electric heating and it uses the electricity price cap of 26.32p per kWh, or your own rate. The energy figures were worked out for a home with a gas boiler, and electric heaters waste less heat than a boiler, so treat the electric saving as a rough upper guide.
Why do floorboards and the loft hatch show no saving?
Nobody we could find publishes a separate saving for those jobs, so we show the cost and leave the saving out rather than guess. They still make rooms feel less draughty, and the Energy Saving Trust counts floors in its whole-home figure.
What should I never block when draught-proofing?
Do not block air bricks, trickle vents, wall vents, extractor fans or flues. They let in the air your home and any gas appliances need. Leave the gap under internal doors, and always take a chimney balloon out before you light a fire.
I rent. Should I draught-proof?
Stick-on foam strips, a letterbox brush and a chimney balloon are cheap and easy to remove. Bigger repairs, such as badly fitting doors or windows, are usually your landlord’s job, so ask them first.
Sources
- Ofgem: Energy price cap unit rates and standing charges, 1 October to 31 December 2026. Gas 7.97p and electricity 26.32p per kWh, average Direct Debit rates for England, Scotland and Wales.
- DECC: Illustrative savings for Green Deal improvement measures (version 1.0, March 2015, now withdrawn), section (g) Draught proofing (GOV.UK page). Energy saved by home type for sealing windows and outside doors.
- Energy Saving Trust: Draught proofing. Around £55 a year for windows, floors and doors, £45 for an unused chimney, around £250 for a professional job.
- Energy Saving Trust: How we calculate our energy saving data (fuel price assumptions). Gas at 6.5p per kWh behind the Energy Saving Trust savings.
- Which?: How to draughtproof your home. Door brush strips from about £6, letterbox covers under £10, keyhole covers about £3.
Figures checked 6 October 2026.