The same double glazing job can be quoted at figures thousands of pounds apart. The way to find a fair price is to get three written quotes after a proper survey, put them side by side on matched spec, and ignore the sales theatre. This guide covers what to compare, what to walk away from, and how to keep your money safe.
Points to take away
- Get three written quotes, each after a home survey. No reliable price comes over the phone.
- Match the spec: frame, style, opening sections, glass, energy rating. “New windows” is not comparable.
- A discount that only exists “today” is a pressure tactic, not a saving.
- Deposit no more than 25 percent, balance on completion, pay by credit card.
- Check FENSA or CERTASS registration and an insurance-backed guarantee.
Reading time: about 6 minutes.
Get quotes you can actually compare
A trustworthy quote follows a home survey: someone measures every opening, checks access and the state of the frames and lintels, and asks what glass and style you want. A number given on the doorstep or over the phone is a starting position for a negotiation, not a quote.
Ask each installer for the quote in writing and itemised. You want to see the same job described three ways, not three different jobs.
The spec that has to match
Copy this into a table and fill it in for each quote. If a box is blank, ask.
| Item | Quote A | Quote B | Quote C |
|---|---|---|---|
| Frame material and colour | |||
| Window style (casement, sash, tilt and turn) | |||
| Opening sections per window | |||
| Glass: Low-E coating | |||
| Glass: gas fill (argon) | |||
| Spacer bar (warm edge vs aluminium) | |||
| Safety or acoustic glass where needed | |||
| Window energy rating or U-value | |||
| Trickle vents included | |||
| FENSA or CERTASS certificate | |||
| Guarantee length and insurance-backed? | |||
| Making good (plastering the reveals) | |||
| Rubbish removal | |||
| Full price including VAT | |||
| Deposit and payment terms |
Two of the biggest silent price differences are the spacer bar (a warm-edge composite spacer performs better than the old aluminium one) and the number of opening sections (each opener costs more than a fixed pane, so a quote with fewer openers looks cheaper but ventilates worse).
Sales tactics to walk away from
- “This price is only good if you sign today.” A real quote does not expire overnight. This is designed to stop you getting the other two.
- A very high opening price that drops by thousands when you hesitate. If the discount was always available, the first number was not honest.
- A “show home” or “area promotion” discount in exchange for signing now or letting them use photos of your house.
- Refusing to leave a written quote without a decision.
- Pushing long finance and quoting only the monthly figure. Always get the total cost with interest.
- A large deposit demand, 40 percent or more, or full payment before the windows are made.
None of this means the company is a fraud. It means their first offer is not their best, and you are better off with a quieter, itemised quote from a local installer to compare against.
Protect your money
- Deposit: 25 percent maximum. The balance is due on satisfactory completion, not on delivery or on the day work starts.
- Pay the deposit by credit card. Anything over £100 gets Section 75 protection, so your card provider is jointly liable if the company takes the money and does not deliver.
- Insurance-backed guarantee (IBG): the guarantee should be underwritten by an insurer so it still stands if the installer stops trading. Ask for the IBG certificate, not just a promise.
- FENSA or CERTASS: confirm registration on the scheme’s website before you pay. Our guide to FENSA vs CERTASS explains what the certificate does.
After you choose
Get the agreed spec, price, start date and completion terms in a signed contract. On completion, check every window opens, closes and locks, the reveals are made good, and the trickle vents work. Keep the FENSA or CERTASS certificate and the guarantee together, and expect the scheme certificate to arrive by post within about 30 days.
For fitted prices to sense-check your quotes against, see our double glazing cost guide.
Get a free quote and we will match you with vetted local installers who quote after a proper survey, with no doorstep pressure.