Window Energy Ratings Explained: A, B, C and What They Mean

Window Energy Ratings were introduced to help homeowners make sense of glazing performance — in the same way appliance ratings help with fridges and washing machines. But the WER scale has quirks that are worth understanding before you buy.

What This Guide Covers

• WER runs from A++ (best) to E — all replacement windows must be C-rated or better under Building Regs
• The rating combines solar gain, thermal transmittance, and air leakage into a single score
• A-rated windows are the sweet spot for most London homes — the cost premium over B is small
• A++ and A+ deliver marginal improvement over A for most homes — rarely worth the added cost
• The WER is for the whole window (frame + glass) — a cheap frame can pull down an otherwise good unit

Introduction

London homeowners face unique challenges when it comes to glazing — from period properties with sash windows in conservation areas, to modern developments requiring structural glass installations. Getting the right advice before you commit can save you significant time and money.

At BuilderFix Glazing, we have completed thousands of glazing jobs across Greater London and Surrey — from emergency repairs in Kensington and Chelsea, to bespoke walk-on glass installations in Mayfair and Belgravia. This guide is based on real experience and the questions our customers ask us most often.

What Does This Typically Cost in London?

Costs vary depending on the type and size of work, the glass specification, frame material, and access. As a general guide, always obtain a free written quote before committing — this protects you from unexpected charges.

At BuilderFix Glazing, we provide free, no-obligation written quotes for all work. Our prices are transparent and fixed before we start — no surprises on the invoice.

What to Ask When Getting a Quote

• Is the price fixed, or could it change once work starts?
• What glass specification is included?
• Are all fixings, sealants and finishing included?
• What compliance documentation will I receive?
• What happens if there is an issue after completion?