The double-glazing salesperson knocks on a Tuesday evening. They sit on your sofa, measure your windows, talk for an hour and a half, and produce a quote of £14,000. Then they "phone the manager" and produce a discount. If you sign tonight, it's £8,500. If you wait until tomorrow, the discount disappears.
This is the national double-glazing industry's main sales technique, and it has been for forty years. The price didn't go from £14,000 to £8,500 because the manager was feeling generous. The £14,000 price was never real. It was the anchor price designed to make £8,500 feel like a saving. The £8,500 quote is, in turn, typically £2,000-£3,000 above what a competent local installer would have charged for the same windows.
Three quotes from local specialists, plus one quote from a national brand for benchmarking, takes about a week of evening calls and produces a 20-40% saving versus the national-brand-only approach.
Why the price gap exists
National brands aren't lying about their windows. The windows themselves are often perfectly good — A-rated, FENSA-certified, manufacturer-warrantied. What you're paying for in the price differential is the cost structure underneath the price tag.
National companies run TV advertising, sponsor sports events, maintain hundreds of vans across the country, employ commission-based salespeople whose income depends on closing high quotes, and operate from regional offices that need rent paying. Every window they sell carries a share of all of that.
Local specialists operate one or two vans, employ the people who actually do the fitting, get most of their work from word-of-mouth or local search, and don't pay a salesperson commission on the quote. The same window from the same factory ends up costing 25% less.
The big-brand premium isn't quality; it's marketing overhead. For UK homeowners willing to manage three quotes themselves, that overhead is avoidable.
The numbers, roughly
Indicative UK double-glazing pricing in April 2026, per window:
| Window type | Local specialist | National brand |
|---|---|---|
| Standard uPVC casement | £450-£800 | £700-£1,200 |
| Sash window (timber) | £900-£1,500 | £1,400-£2,200 |
| Aluminium frame casement | £700-£1,200 | £1,000-£1,800 |
| Bay window | £1,400-£2,200 | £2,000-£3,500 |
For a typical 3-bed semi with 10-12 windows: £5,000-£10,000 from a competent local specialist, £8,000-£15,000 from a national brand, with the windows themselves often being functionally identical or very close.
The exception is genuinely specialist work — heritage sash windows, conservation area requirements, unusual frame materials. Some national brands handle these competently; many don't. A specialist sash-window installer will usually beat both options for that work.
What actually matters in a window
The window itself comes down to three things:
U-value. Modern A-rated windows hit 1.2-1.4 W/m²K. Anything labelled A-rated will do this; the difference between A and A++ is real but marginal in cost-benefit terms.
Frame material. uPVC is cheapest, lowest-maintenance, looks fine on most modern houses, looks wrong on Edwardian terraces. Aluminium has slim profiles that maximise the glass area, costs more, well-suited to contemporary architecture. Timber is heritage-correct for period properties and requires repainting every 8-12 years.
Installer quality. Equal in importance to the window itself. A perfect window badly fitted leaks, condenses, and underperforms. A budget window well fitted outperforms a premium window stuffed in by a hurried installer. The fitting is what FENSA or Certass certification is meant to standardise; verify the installer has the certificate, and check Google reviews specifically for fit quality.
What doesn't really matter at this price tier: brand prestige (the windows are made in the same factories), "premium glass" upsells (most are minor variants), or decorative flourishes that double the cost without changing performance.
Triple glazing: usually no
Triple glazing comes up in every double-glazing quote because the upsell is profitable. The honest answer for most UK homes: A-rated double glazing is enough.
Triple glazing reduces window heat loss by another 20-30% versus A-rated double, which sounds significant until you do the maths. The total heat loss through windows in a typical UK home is roughly 10-15% of total heat loss. Cutting that by 25% saves you 2.5-4% of total heating cost — about £40-£80/year on a typical heating bill. The triple glazing premium of £150-£250 per window adds £1,500-£3,000 to the project cost, with a payback period of 25-50 years.
Triple glazing makes sense in three specific situations: passive house standard new builds, homes in genuinely cold areas (rural Scotland and Wales), and rooms next to busy roads where the acoustic benefit matters more than the thermal one. For typical English semi-detached homes, double glazing is the right specification.
The savings reality
Window replacement is sold on energy savings, but the maths is honest about what they are.
Single-glazed to A-rated double: 20-30% reduction in heat lost through windows. For a typical UK 3-bed semi, that's £150-£280/year on the heating bill.
Old double-glazing (1990s vintage) to modern A-rated double: 10-15% reduction in heat lost through windows. About £80-£150/year for a typical 3-bed semi.
Payback period for full window replacement on a typical home: 15-25 years for single-to-double, 25-40 years for old-double-to-modern-double.
Which means: if you're replacing windows purely for energy economics, the case is weak. The case becomes strong when you factor in comfort (cold draughts gone, condensation gone), aesthetics (the right windows transform a house), property value (estate agents do price double glazing into asking prices), and acoustic performance (sleeping next to a road improves dramatically).
For homeowners optimising purely for heat loss reduction, loft insulation, cavity wall insulation, and draught-proofing all have shorter payback periods than window replacement and should usually go first.
How to handle the quote process
What works for UK homeowners replacing windows:
Start with three local installer quotes. Find them through Checkatrade, MyBuilder, or — most reliably — by asking neighbours who've had work done in the last five years and walking past the house to inspect the windows. Local installers are accountable to their local reputation in a way national chains aren't.
Get one national-brand quote for comparison. Anglian, Everest, or Safestyle will all happily come and produce one. Don't sign anything during the home visit; anything they offer that night will still be available next week, regardless of what they say.
Ask for itemised quotes. The total price obscures whether the difference is in the windows themselves, the fitting, the trickle vents, the disposal of the old units, or the "scaffolding hire" that wasn't on the cheaper quote. Quote-to-quote comparison only works if you can match the line items.
Verify FENSA or Certass certification. Without it, the installer can't self-certify building regulations compliance, which means the windows won't legally count when you sell the house and the warranty is unenforceable. The certificate number should appear on the quote.
Don't sign on the first visit. Every "today only" discount is a sales tactic. The price next week will be functionally the same. Sleep on it. Compare three quotes side by side. Phone references from each installer if you have any doubt.
For period properties, listed buildings, or conservation areas: skip the national brands entirely and find a specialist installer who does sash windows or heritage frames as their main work. Conservation officer at the local council is a useful first call to identify reputable specialists in your area.
Building regulations bits
A few things that should be on every quote:
FENSA or Certass certificate number, allowing the installer to self-certify compliance.
Trickle vents, required by 2022 building regulations on most replacement windows. Some installers leave them off and rely on the homeowner not noticing; the installation isn't compliant without them.
Disposal of old windows, often £50-£150 of cost; some quotes hide this as a separate line item, some bundle it.
Conservation area or listed building considerations, where applicable; the installer should know whether your specific property has restrictions.
If any of these are missing from a quote, ask why. Reputable installers handle them automatically; ones that don't are cutting corners.
What I'd actually do
Three local quotes, one national-brand quote for benchmark, all itemised, none signed on the first visit, all with FENSA or Certass numbers. Sleep on it. Pick the local quote with the best reputation that's within 10% of the cheapest local quote. Refuse the national-brand "today only" discount.
The £2,000-£4,000 saved on a typical job covers a lot of the insulation and draught-proofing work that pays back faster anyway.
This article is general consumer information about UK double glazing, not building services advice. UK home improvements at this scale benefit from professional consultation; use FENSA / Certass certified installers.
Affiliate disclosure: Morningfold has affiliate partnerships with Checkatrade, MyBuilder, and several UK glazing installer networks. See editorial standards.