EPC Rating Impact Calculator

Upgrading from single glazing to A-rated double glazing can improve your EPC by 8-15 points, potentially moving you up one or two EPC bands. Replacing old double glazing (pre-2002) with modern A-rated units typically adds 3-8 points. The exact improvement depends on your property type, age, number of windows, and current insulation levels. Larger, older properties with more windows tend to see the biggest improvements.

Since April 2020, landlords in England and Wales cannot let properties with an EPC rating below E under the Minimum Energy Efficiency Standards (MEES) regulations. Non-compliance can result in fines of up to £5,000 per property. The government has proposed raising this minimum to EPC C by 2030, making it important for landlords to plan window upgrades now to future-proof their rental properties.

Yes, windows are one of the key factors assessed in an EPC survey. Windows account for approximately 10-20% of a home's heat loss, making them a significant contributor to your overall energy efficiency score. The EPC assessor evaluates glazing type (single, double, or triple), frame material, age of the windows, and their overall thermal performance. Modern A-rated double glazed or triple glazed windows can substantially improve your rating.

The Energy Saving Trust estimates that replacing single glazing with A-rated double glazing in a typical UK semi-detached home saves approximately £170-£235 per year on energy bills. Upgrading from old double glazing to modern A-rated units can save £80-£150 annually. Additionally, improved EPC ratings can add 5-10% to your property value, making new windows an excellent investment for both running costs and capital value.

Most UK government energy efficiency grants, including the ECO4 scheme and the Warm Homes: Local Grant, require your property to have an EPC rating of D or below (D, E, F, or G) to qualify. Properties rated D or below are prioritised for funding because they have the most room for improvement. If your property currently has a low EPC rating, you may be eligible for grants that cover some or all of the cost of new windows. Use our Window Grants Checker to see what funding you might qualify for.

An EPC assessor evaluates your windows as part of the overall property survey using the Standard Assessment Procedure (SAP). For windows, they assess: the glazing type (single, double, or triple), the gap between panes, the gas fill (air, argon, or krypton), the frame material (uPVC, timber, aluminium), and any low-emissivity coatings. Each factor contributes to the window's U-value, which measures thermal performance. Lower U-values indicate better insulation and contribute to a higher EPC score. Learn more about window thermal performance with our U-Value Calculator.