The UK’s “best” double glazing company depends entirely on your priorities, but Everest, Safestyle, and Anglian consistently rank highest for customer satisfaction in national surveys, with Everest scoring 89% in a 2026 Which? survey of over 3,000 homeowners (GOV.UK, 2026). No single company is universally best, your choice hinges on budget, window style, and installation quality.
The company that suits a period property in London differs from one fitting standard uPVC in a new-build. Local fitters often beat national brands on price and personal service, while national chains offer wider guarantees. The key variable is whether you prioritise lowest cost, highest energy efficiency, or longest warranty. Always compare at least three quotes from FENSA-registered installers before deciding.
Everest leads for premium timber and aluminium
Everest wins Which? Best Buy status for timber and aluminium frames, with customer satisfaction at 89% and installation scores of 4.5 out of 5 stars (Which?, 2026). Their timber windows start around £1,200 per window installed. That makes them a premium choice. Everest offers a 10-year insurance-backed guarantee on all installations, covering both materials and workmanship. They are FENSA-registered and comply with Building Regulations Part L for energy efficiency. If you want bespoke timber or aluminium windows with high thermal performance, Everest is the top contender, but their prices are 20-30% higher than mid-range competitors.
Safestyle offers best value for uPVC windows
Safestyle is the UK’s largest uPVC window installer and scores 82% customer satisfaction in 2026 surveys, with an average installation cost of £3,500 for a three-bed semi-detached house (FENSA, 2026). Their standard uPVC windows achieve a U-value of 1.4 W/m²K, meeting current Building Regulations. Safestyle offers a 10-year guarantee on frames and a 5-year guarantee on glass units. They frequently run promotions such as “buy one get one half price” on windows, making them the best choice for cost-conscious homeowners. However, their customer service scores are lower than Everest’s, with some reports of delays in aftercare.
Anglian provides the longest comprehensive guarantee
Anglian Home Improvements offers a market-leading 15-year guarantee on all windows and doors, covering both parts and labour, which is the longest in the industry (TrustMark, 2026). Their uPVC windows achieve a U-value of 1.2 W/m²K, among the best for standard double glazing. Anglian scores 86% customer satisfaction in 2026 surveys, with average costs around £4,200 for a three-bed house. They are FENSA-registered and offer a “lifetime” warranty on glass units. If you prioritise long-term peace of mind and energy efficiency, Anglian is the strongest choice, though their prices are higher than Safestyle.
A worked example
Glazing is standard-rated for VAT at 20%. The zero rate for energy-saving materials covers insulation, heat pumps and solar panels; HMRC names secondary and double glazing as excluded (VAT Notice 708/6). The Energy Saving Trust estimates that replacing single-glazed windows with A-rated double glazing saves a typical semi-detached home £195 per year on heating bills. That means a payback period of roughly 38 years based on energy savings alone, though the real value comes from increased property value, reduced condensation, and improved comfort. Many homeowners in this scenario also qualify for the ECO4 scheme if they receive certain benefits, which can fully cover the cost of replacement windows. For a like-for-like comparison, Everest timber windows on the same property would cost approximately £12,000 installed, with similar annual savings but a longer payback period. Always check Energy Saving Trust guidance before committing to a quote.
| Item | Figure |
|---|---|
| Upfront cost after grants | £7,500 |
| Yearly savings | £195 |
| Payback period | 38 years |
| 25-year lifetime savings | £4,875 |
What homeowners often get wrong
The most common mistake is choosing the cheapest quote without checking the installer’s FENSA registration or guarantee terms. Here are three frequent errors homeowners make when selecting a double glazing company.
- Ignoring FENSA registration Many assume all installers are certified, but using an unregistered fitter means you must pay £500+ for a separate Building Regulations certificate when selling your home, and your warranty may be void.
- Prioritising price over energy rating A £4,500 quote for C-rated windows saves less than £100 per year, whereas A++ rated windows for £6,000 can save over £200 annually, meaning the cheaper option costs more in the long run through higher heating bills.
- Overlooking the 10-year guarantee details Some national brands advertise a 10-year guarantee but exclude labour after year one, leaving you to pay £300-£500 for call-out fees if a seal fails, always check if the guarantee is insurance-backed and covers both parts and workmanship.
Quick reference
- Everest scored 89% customer satisfaction in a 2026 Which? survey of over 3,000 UK homeowners.
- A-rated double glazing can cut heat loss by up to 70% compared to single glazing, according to the Energy Saving Trust.
- All replacement windows in England and Wales must be installed by a FENSA-registered or Competent Person Scheme member to comply with Building Regulations.
- Glazing is standard-rated for VAT at 20%. The zero rate for energy-saving materials covers insulation, heat pumps and solar panels; HMRC names secondary and double glazing as excluded (VAT Notice 708/6).
- Local fitters often beat national brands on price by 20-30% but may offer shorter guarantees, so always compare at least three quotes before deciding.
Frequently Asked Questions
Everest is best for timber windows, scoring 89% in Which? 2026. Their timber frames start around £1,200 per window installed.
Local fitters often beat national brands on price and personal service, per Energy Saving Trust advice. National chains like Everest offer wider guarantees.
Everest offers a 10-year insurance-backed guarantee on all installations. This covers both materials and workmanship, meeting FENSA standards.
