Energy efficient windows: what would yours save?
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Your windows lose heat at a U-value of about 5.0, roughly 3.6 times what a new window is allowed to in England (1.4).
The Energy Saving Trust puts the saving for a single-glazed semi-detached house at about £85 a year and 290 kg of CO2 (GB, checked October 2026). Yours depends on your house and how you heat it.
New A-rated windows for a mid-terrace house (6 windows) cost £5,090 – £9,254 fitted. People replace windows for warmth, quiet and less condensation as much as for the bill.
Your windows lose heat at a U-value of about 5.0, roughly 3.6 times what a new window is allowed to in England (1.4).
The Energy Saving Trust puts the saving for a single-glazed semi-detached house at about £85 a year and 290 kg of CO2 (GB, checked October 2026). Yours depends on your house and how you heat it.
New A-rated windows for a semi-detached house (8 windows) cost £6,774 – £12,317 fitted. People replace windows for warmth, quiet and less condensation as much as for the bill.
Your windows lose heat at a U-value of about 5.0, roughly 3.6 times what a new window is allowed to in England (1.4).
The Energy Saving Trust puts the saving for a single-glazed semi-detached house at about £85 a year and 290 kg of CO2 (GB, checked October 2026). Yours depends on your house and how you heat it.
New A-rated windows for a detached house (12 windows) cost £9,702 – £17,640 fitted. People replace windows for warmth, quiet and less condensation as much as for the bill.
Your windows lose heat at a U-value of about 2.8, roughly 2.0 times what a new window is allowed to in England (1.4).
There is no official saving figure for replacing double glazing. It is less than for single glazing, because your glass already keeps much of the heat in.
New A-rated windows for a mid-terrace house (6 windows) cost £5,090 – £9,254 fitted. People replace windows for warmth, quiet and less condensation as much as for the bill.
Your windows lose heat at a U-value of about 2.8, roughly 2.0 times what a new window is allowed to in England (1.4).
There is no official saving figure for replacing double glazing. It is less than for single glazing, because your glass already keeps much of the heat in.
New A-rated windows for a semi-detached house (8 windows) cost £6,774 – £12,317 fitted. People replace windows for warmth, quiet and less condensation as much as for the bill.
Your windows lose heat at a U-value of about 2.8, roughly 2.0 times what a new window is allowed to in England (1.4).
There is no official saving figure for replacing double glazing. It is less than for single glazing, because your glass already keeps much of the heat in.
New A-rated windows for a detached house (12 windows) cost £9,702 – £17,640 fitted. People replace windows for warmth, quiet and less condensation as much as for the bill.
Your windows lose heat at a U-value of about 2.0, roughly 1.4 times what a new window is allowed to in England (1.4).
There is no official saving figure for replacing double glazing. It is less than for single glazing, because your glass already keeps much of the heat in.
New A-rated windows for a mid-terrace house (6 windows) cost £5,090 – £9,254 fitted. People replace windows for warmth, quiet and less condensation as much as for the bill.
Your windows lose heat at a U-value of about 2.0, roughly 1.4 times what a new window is allowed to in England (1.4).
There is no official saving figure for replacing double glazing. It is less than for single glazing, because your glass already keeps much of the heat in.
New A-rated windows for a semi-detached house (8 windows) cost £6,774 – £12,317 fitted. People replace windows for warmth, quiet and less condensation as much as for the bill.
Your windows lose heat at a U-value of about 2.0, roughly 1.4 times what a new window is allowed to in England (1.4).
There is no official saving figure for replacing double glazing. It is less than for single glazing, because your glass already keeps much of the heat in.
New A-rated windows for a detached house (12 windows) cost £9,702 – £17,640 fitted. People replace windows for warmth, quiet and less condensation as much as for the bill.
Your windows already meet today’s standard.
New windows would save next to nothing on heating.
Replace them only if they have failed: misted units, rotten or warped frames, or locks that no longer hold.
Your windows already meet today’s standard.
New windows would save next to nothing on heating.
Replace them only if they have failed: misted units, rotten or warped frames, or locks that no longer hold.
Your windows already meet today’s standard.
New windows would save next to nothing on heating.
Replace them only if they have failed: misted units, rotten or warped frames, or locks that no longer hold.
Saving: the Energy Saving Trust’s figure for a single-glazed semi (GB, checked October 2026), not our own. Prices: our planning estimates, standard white uPVC casements.
What the energy rating means
Windows are rated from A++ (best) to E by the British Fenestration Rating Council. The rating looks at the whole window, frame and glass together: how much heat it lets out, how much it lets in from the sun, and how much air leaks round it.
The U-value on the label is the heat-loss part alone: the lower it is, the less heat escapes. Single glazing loses heat at a U-value of roughly 5; double glazing from the 1990s at about 2.8; a new A-rated window at around 1.2 to 1.4.
The legal minimum for a replacement window
In England, a replacement window must reach a U-value of 1.4 W/m²K or better, or a Window Energy Rating of band B or better (Building Regulations Approved Document L, 2021). Single glazing cannot meet it, so every replacement is at least double glazed.
A FENSA or CERTASS registered installer certifies this for you, so you do not need to apply to building control yourself. Keep the certificate: you will be asked for it when you sell.
What A-rated windows cost, by house
| House | Windows | New windows fitted, inc VAT |
|---|---|---|
| Mid-terrace | 6 | £5,090 – £9,254 |
| Semi-detached | 8 | £6,774 – £12,317 |
| Detached | 12 | £9,702 – £17,640 |
Do new windows pay for themselves?
Not on energy alone. The Energy Saving Trust puts the saving at about £85 a year for a single-glazed semi (checked October 2026), against £6,774 – £12,317 for its new windows fitted. Anyone selling windows as a way to save money is selling the wrong thing.
What you do get, straight away: a warmer house with no draughts or cold spots by the glass, far less condensation, a quieter house, better locks, and frames that will not rot. That is why people replace windows, and it is reason enough.
What is included in these prices
Supplying and fitting the new windows, taking out and taking away the old ones, and sealing and making good around each new frame. VAT is in every figure.
Access for upstairs windows is included where the estimate needs it (£936 a job for a scaffold tower), and small jobs carry a minimum charge of £970. Not included: new sills or lintels where the old ones have failed, internal decorating, and anything structural.
How these prices compare with other UK guides
Published guides often come in lower. Checkatrade’s window cost guide (last updated July 2026) puts a standard 1,200 × 1,200 mm uPVC casement at £450–£550 plus VAT, about £540–£660 with VAT, and a 3-bedroom house with 12 windows at £5,000–£10,000 plus VAT.
Our figure for the same standard window is about £745 including VAT, for the window itself, fitted, as part of a larger job. It is built from what these jobs typically settle at with established installers. Our estimates then add taking the old frames away, making good and, where needed, access for upstairs windows, which is why the table above, and our £847 to £1,540 a window on an eight-window job, work out at more per window than this. A smaller local firm may quote less than our range; some national companies quote at the top of it.
Whichever figure you use, compare quotes like for like: check each one says whether removal, access, making good and VAT are included.
Planning estimate or quotation?
Every figure on this page is a planning estimate: what a job like this typically costs, for budgeting and for judging the quotes you get. It is not a quotation. A quotation comes from an installer after a survey, when the exact sizes, specification and condition of your house are known.
Facet Pro narrows the estimate to your own house from a photograph of the front — the windows it can see, the wall it can measure against your front door — and says which parts are measured and which are estimated for your house type. Your installer confirms the figure on survey.
Common questions
How much do energy efficient windows save a year?
About £85 a year for a semi-detached house going from single glazing to A-rated double glazing, according to the Energy Saving Trust (checked October 2026), and roughly 290 kg of CO2. Less if you already have double glazing.
What is the minimum energy rating for replacement windows?
In England a replacement window must reach a U-value of 1.4 W/m²K or a Window Energy Rating of band B or better (Approved Document L, 2021).
Is A++ worth it over A-rated?
Usually not on bills: the difference between A and A++ on a whole house is a few pounds a year. A++ is normally triple glazing, which is worth considering for comfort or noise, not as an investment.
Is it worth replacing old double glazing?
For energy alone, rarely: double glazing already keeps much of the heat in, and there is no official figure for what replacing it saves. It is worth it when the units have misted, the frames have failed, or the house is cold and draughty around them.
Do I need building regulations approval for new windows?
Not separately, if a FENSA or CERTASS registered installer fits them: they certify that the windows meet the regulations and register the work for you.
Facet Pro is in early access. We are starting to check how we measure wall area from a photograph against surveyed properties, so treat wall and roof figures as indicative and window figures as a guide.
Your house isn’t average.
See this project on your own home and get a planning estimate. Any figure on this page is for a typical house. Start with one photograph of the front and we will find your windows, doors, roof and walls, estimate your wall area, and price your own elevation.
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These are planning estimates — not a quotation, and not a survey. Windows and doors: what these jobs typically sell for, from 25 years in the home improvement industry, checked against current UK prices. Render, roof and roofline: UK material and labour rates, with scaffolding, waste and VAT. What you pay depends on your own house and, more than anything else, on which company quotes it. Your installer confirms the figure on survey. Prices checked October 2026.