Should You Choose the Cheapest Double Glazing Quote?
Sometimes the cheapest quote is simply the best value. More often it is missing something. Here is how to tell the difference in under ten minutes.
Key takeaways
- A lowest quote within 10% of the others is usually genuine and worth taking.
- A quote 25% or more below the field almost always excludes something important.
- Check disposal, making good, certification, scaffolding and the guarantee before deciding.
- Price is only one of four factors; installation quality and aftercare matter as much.
The instinct to pick the lowest number is understandable and occasionally correct. A local independent with low overheads can legitimately undercut a national firm by 20% for the same work. The skill is separating that from a quote that is cheap because it is not the same job.
When cheapest is genuinely best
- The gap to the next quote is small, typically under 10%.
- The scope is identical: same profile, same glass, same inclusions.
- The firm is local, registered and has verifiable recent customers.
- The guarantee and certification match the other quotes.
- The survey and the conversation felt professional rather than rushed.
When cheapest is a smaller job
| Missing item | What you pay later |
|---|---|
| Disposal | £10 – £25 per window |
| Making good and plastering | £300 – £800 per house |
| Scaffolding | £500 – £1,500 |
| FENSA or CERTASS certificate | Cost of a building control application |
| Insurance-backed guarantee | Nothing, if the firm stops trading |
| Toughened or safety glass | Replacement panes at your cost |
| Trickle vents | Remedial work to satisfy ventilation rules |
The three cheaper-things you should not accept
- No certification. Without FENSA or CERTASS registration you may have no compliance certificate when you sell.
- No written guarantee, or one that is not insurance-backed, on a job of several thousand pounds.
- A deposit that is most of the contract value. Your money should not fund the whole job in advance.
A fair way to choose
Rank the three quotes on scope first, then on price, then on the firm: how long it has traded, who fits the windows, and what its customers say about aftercare. If your instinct and the evidence point to the middle quote, take the middle quote. The difference between the cheapest and the best is usually a few hundred pounds, which is roughly the cost of one remedial visit.
The bottom line
Choose the cheapest quote only when the scope, certification and guarantee match the others. Otherwise you are not buying cheap windows, you are buying a small job with a large bill attached.
Frequently asked questions
Cheap can be excellent value when the specification and scope match the market. Cheap because something is missing usually costs more within two years.
A 5% to 10% gap is normal and often reflects lower overheads. Beyond 20% to 25%, expect to find a missing inclusion.
Poor sealing, draughty frames, no certificate, and no one to call when a problem appears. The windows may look fine on day one and fail within a couple of winters.
Not for the brand alone. Pay for the specification, the installation team and the guarantee. A well-fitted mid-market profile beats a badly fitted premium one.
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