What type of property?
This helps estimate the energy impact of new windows.
Estimates based on typical property data. Actual improvements depend on property-specific factors. thewindowhub.co.uk ltd, G25 National Installer of the Year.
How new windows change an EPC rating
An Energy Performance Certificate scores a home from 1 to 100 and places it in a band from A to G. Glazing is one of the inputs, alongside insulation, heating and hot water. Single glazing and early double glazing without a low-emissivity coating lose heat quickly, so replacing them is one of the higher-impact changes a homeowner or landlord can make.
Across our installations in Bristol, Exeter, Cardiff and the surrounding areas we typically see these improvements: replacing single glazing with A-rated or A++ double glazing adds 15 to 28 points; replacing pre-2002 double glazing adds 8 to 18 points; upgrading post-2002 double glazing to A++ units adds 5 to 10 points. The exact figure depends on the property type, its current glazing and its overall condition, which is why the calculator above asks for those three things.
Landlords: EPC C by 1 October 2030
Private rented homes in England and Wales must reach EPC band C by 1 October 2030. Where that is not achievable, landlords will need to show they have spent up to the cost cap, currently £10,000 per property, before registering an exemption. Money spent on eligible measures from 1 October 2025 counts towards the cap. A typical three-bedroom rental with eight windows can be upgraded to A++ double glazing for around £3,500 to £5,500, so windows fit comfortably inside it. Our landlord guide sets out the rules in full.
What has changed in 2026
The reformed EPC, which adds a separate Fabric Performance score for walls, roof, floors and windows, has been delayed to the second half of 2027. The landlord deadline has not moved. Our EPC guide explains the reform and what it means for glazing.
What to do next
Run the calculator, then book a free home survey. Our surveyor will look at the whole property, tell you honestly whether windows alone will reach the band you need, and quote for the right specification. Every installation is FENSA registered (39576) and covered by our 15-year guarantee with Installsure insurance backing. If condensation or draughts are what prompted you, our guides on condensation and draughty windows explain what each symptom means before you spend anything.
EPC questions we are asked most
Will new windows take my home from EPC D to EPC C?
Sometimes on their own, often not. The gap between band D and band C is usually 10 to 15 points, and a full set of A-rated windows typically adds 5 to 28 points depending on what they replace. If you are near the top of band D, windows can bridge the gap alone; from the bottom of D you will usually need insulation or heating improvements as well. Our surveyor will tell you honestly which applies.
Has the landlord EPC C deadline changed?
No. The reform of the certificate itself has moved to the second half of 2027, but private rented homes in England and Wales still need to reach EPC C by 1 October 2030, with a cost cap of £10,000 per property.
Do I get a new EPC after new windows are fitted?
Not automatically. An accredited assessor produces the certificate. Keep your FENSA certificate and our installation paperwork, as the assessor will use them as evidence of the glazing upgrade.
Is there VAT relief on new windows?
No. The 0% VAT rate on energy-saving materials covers items such as insulation and heat pumps, not replacement windows and doors, which are charged at 20%.
How accurate is this calculator?
It is an estimate from typical property data, not an assessment. It is meant to show the scale of improvement so you can decide whether a survey is worthwhile. Every quote follows a free home survey.