The short answer
Get at least three quotes from FENSA or CERTASS registered installers, all on the same specification, and insist on an itemised written quote after a proper survey rather than a phone-only price. Tell each installer the same brief — how many windows and doors, the frame material, the glass and energy rating you want — so the quotes are comparable. Then line them up item by item and weigh price alongside guarantee, survey quality and reviews. See how to choose a window installer for the checks that matter.
Getting quotes is the step where homeowners most often end up comparing apples with pears — one quote includes a better glass spec or a longer guarantee, another leaves out the certificate or making good. This guide explains what to tell installers, what a good quote should contain, and how to compare three quotes fairly. We are an independent information and introduction service: we do not fit windows, and we publish this guidance free.
Getting quotes at a glance
- How many At least three
- Same brief Identical spec to each
- Survey On-site, not phone-only
- Format Itemised, in writing
- Registration FENSA or CERTASS
- Compare on Like-for-like spec
What to tell each installer
To get comparable quotes, give every installer the same brief. The more precise you are, the less room there is for quotes to drift apart on hidden differences. Cover the number and type of openings, the frame material, the glass and energy rating, the colour and style, and any access issues such as upper floors needing scaffolding. Ask each to survey the property rather than quote over the phone, because a measured survey is what makes a quote reliable.
| Tell the installer | Why it matters |
|---|---|
| Number & type of windows/doors | The core of the quote — must match across all three |
| Frame material | uPVC, aluminium or timber changes price significantly |
| Glass spec & energy rating | Double vs triple, acoustic glass, WER band |
| Colour & style | Non-standard colours and bay windows add cost and lead time |
| Access | Upper-floor scaffolding and awkward access affect price |
What a good written quote includes
A quote you can rely on is itemised and in writing, not a single headline figure. It should set out the windows and doors covered, the frame material, the glass and energy rating, the guarantee length and terms, who notifies the work under Building Regulations, and what is included for making good and removing the old frames. If a quote is vague about any of these, ask for it to be spelled out before you compare.
How to compare quotes fairly
With three written quotes on the same brief, line them up item by item. A price gap often comes down to one quote including a better glass spec, a longer guarantee, or scaffolding that another omitted — adjust for anything missing before judging on price. Sense-check the figures against typical costs in our double glazing cost guide, then weigh the things price alone does not capture: the quality of the survey, the clarity of the guarantee, independent reviews and how the installer communicated. The cheapest quote is not automatically the best value, and the most expensive is not automatically the safest. These are general pointers, not advice for your specific job.
Compare double glazing quotes
Get matched with FENSA or CERTASS registered window installers in your area, then apply these checks to compare on a like-for-like spec. Free to use, no obligation — we are an independent guide, not an installer.
Frequently asked questions
How many double glazing quotes should I get?
At least three, all on the same specification — same number and type of windows, frame material, glass and energy rating. This lets you compare fairly and spot a quote that is cheap only because it leaves something out.
Should I get a survey or a phone quote?
Insist on an on-site survey. A measured survey is what makes a quote reliable; a phone-only or online estimate can change significantly once an installer sees the openings, access and any repairs needed. A proper survey also lets you judge how the installer works.
What should a double glazing quote include?
An itemised written quote should list the exact windows and doors, frame material and colour, glass spec and energy rating, guarantee terms, Building Regulations notification via FENSA or CERTASS, making good and waste removal, and the deposit and payment schedule. Ask for anything vague to be spelled out.
Is the cheapest double glazing quote the best?
Not necessarily. A lower price can mean a thinner glass spec, a shorter guarantee or omitted work such as scaffolding or making good. Compare on a like-for-like specification and weigh the guarantee, survey quality and reviews, not just the headline figure.
Sources & further reading
- FENSA / CERTASS — finding and checking registered installers
- Glass and Glazing Federation (GGF) — getting quotes and consumer protection
- Energy Saving Trust — quotes for replacement windows
- GOV.UK / Building Regulations — standards for replacement windows
This is general information, not advice for your specific situation, and not a quote. We are an independent information and introduction service — we do not fit windows or provide quotes ourselves; we can connect you with a FENSA or CERTASS registered window installer. Figures are typical illustrations, not quotes.