Old or draughty windows are one of those home problems you can feel but often put off dealing with. Either the heating bills keep creeping up, the frames are rotting, or condensation between the panes has been there so long you have stopped noticing it. When you finally decide to act, the first question is always the same: what is this going to cost me?
This guide covers the full cost of window replacement in the UK in 2026, broken down by window type, material, and installation scenario, so you know exactly what you are looking at before you call anyone out for a quote.
A standard uPVC casement window replacement costs £400 to £900 installed. Replacing all windows in a typical 3 bed semi costs £3,500 to £7,000. Aluminium windows cost 40 to 60 percent more than uPVC. Sash windows start at £800 per window and can reach £3,000 for timber in a conservation area.
Window Replacement Costs at a Glance
| Window Type | Supply Only | Installed (Per Window) |
|---|---|---|
| uPVC casement (standard) | £150 to £400 | £400 to £900 |
| uPVC sash window | £400 to £900 | £800 to £1,500 |
| Aluminium casement | £300 to £800 | £600 to £1,500 |
| Aluminium sliding sash | £600 to £1,200 | £1,000 to £2,000 |
| Timber casement | £400 to £1,200 | £700 to £1,800 |
| Timber sash window | £600 to £1,800 | £1,000 to £3,000 |
| Bay window (3 pane uPVC) | £1,200 to £2,500 | £2,000 to £5,000 |
| Roof window / skylight | £400 to £1,000 | £800 to £1,800 |
Full House Window Replacement Costs
Most homeowners want to know the total cost to replace all windows in a house. The number depends heavily on how many windows you have and what material you choose.
| Property Type | Typical Window Count | uPVC Installed | Aluminium Installed |
|---|---|---|---|
| 1 bed flat | 4 to 6 | £2,000 to £4,000 | £3,000 to £6,000 |
| 2 bed terraced | 6 to 9 | £2,500 to £5,000 | £3,500 to £7,500 |
| 3 bed semi | 8 to 12 | £3,500 to £7,000 | £5,000 to £10,000 |
| 4 bed detached | 12 to 18 | £5,000 to £10,000 | £7,500 to £16,000 |
What Affects the Cost of New Windows?
Two quotes for window replacement can vary by thousands of pounds. Here is what actually drives the difference.
Material
uPVC is the cheapest and most popular choice. Aluminium costs 40 to 60 percent more but lasts longer and looks better on modern properties. Timber is the premium option and the most expensive, though it is sometimes required in conservation areas and on listed buildings. Composite frames (aluminium outside, timber inside) are available at a price premium of 20 to 30 percent over standard aluminium.
Glazing specification
Standard double glazing (two panes with an argon filled gap) is the default for most replacements. The thermal performance is expressed as a U value — the lower the number, the better the insulation. A typical double glazed unit has a U value of around 1.2 W/m²K. Triple glazing achieves around 0.8 W/m²K and costs 20 to 30 percent more per window. For most UK homes, triple glazing does not pay back the extra cost within a typical window lifespan.
Window style and size
Casement windows (the standard opening type) are the most affordable. Sliding sash windows are more complex mechanically and cost significantly more. Bay windows, arched windows, and non standard shapes are priced individually and carry a premium. Larger windows use more glass and frame material, so the cost scales with size.
Installation complexity
A straightforward like for like replacement where the opening stays the same size is the cheapest scenario. If the opening needs to be enlarged or reduced, if a lintel needs strengthening, or if there is any rot in the surrounding masonry or plasterwork, the labour cost rises. First floor windows requiring scaffolding or access equipment add £200 to £600 to the bill.
Location
London and the South East tend to run 20 to 35 percent higher than the national average for window installation. Yorkshire, the North West, and Scotland are typically at or below average. Rural locations with limited installer competition can be similarly higher.
The company you use
National glazing companies advertise heavily and use commission based salespeople, which inflates their prices considerably. A quote from a national firm is often 30 to 50 percent higher than an equivalent quote from a local independent installer for the same spec window. Always get at least three quotes and check that you are comparing the same specification.
Labour Costs for Window Fitting
| Job | Labour Cost |
|---|---|
| Single casement window (ground floor) | £150 to £300 |
| Single casement window (first floor) | £200 to £400 |
| Sash window replacement | £250 to £500 |
| Bay window (3 pane) | £400 to £800 |
| Full house (8 to 12 windows) | £1,500 to £3,500 |
Most window companies quote an all in price that includes supply, fitting, and removal of the old windows. Ask for the breakdown if you want to compare like for like against other quotes.
uPVC vs Aluminium vs Timber: Which Is Right for You?
| Material | Cost | Lifespan | Maintenance | Best For |
|---|---|---|---|---|
| uPVC | £400 to £900 | 25 to 35 years | Very low | Most homes, maximum value for money |
| Aluminium | £600 to £1,500 | 40 to 45 years | Low | Modern homes, slim sightlines, larger spans |
| Timber | £700 to £3,000 | 60+ years (with upkeep) | High | Period properties, conservation areas, listed buildings |
uPVC: the practical choice
uPVC is the most common window material in the UK for a reason. It is affordable, low maintenance, thermally efficient, and available in a wide range of styles and colours including woodgrain foils that mimic timber. The main limitation is that it does not suit all property types aesthetically, and it cannot be painted if you change your mind about the colour.
Aluminium: the premium mainstream option
Aluminium windows have become considerably more affordable as demand has grown. The key advantage over uPVC is the much slimmer frame profile, which lets in more light and looks better on contemporary properties. Aluminium is also the standard for floor to ceiling glazing and large format windows where uPVC does not have the structural rigidity. The powder coat finish comes in any RAL colour and lasts 25 to 30 years without repainting.
Timber: the heritage option
Timber windows look genuinely beautiful and can last over 60 years with proper maintenance. The maintenance requirement is the catch. Timber needs repainting or re staining every 5 to 7 years, otherwise moisture gets in, the wood rots, and you are looking at expensive repair or early replacement. If you are in a conservation area or own a listed building, timber may not be optional.
Double vs Triple Glazing: Is It Worth It?
Triple glazing is often marketed as a significant upgrade, and in very cold climates it is. For most UK homes, the reality is more nuanced.
The difference in U values between a good double glazed unit (1.1 to 1.2 W/m²K) and triple glazing (0.7 to 0.8 W/m²K) is meaningful in energy terms, but the payback period on the extra cost can be 15 to 20 years depending on your energy use. For a 3 bed semi replacing 10 windows, triple glazing might add £2,000 to £4,000 to the bill for energy savings of £50 to £150 per year.
Where triple glazing does make clear sense is in very exposed properties with high heating bills, in new builds targeting high energy performance ratings, or where noise reduction from the extra pane is a specific requirement.
Unless you have a specific reason (high heat loss, noise issues, energy performance target), the best double glazing with a quality installation will perform well and give you better value for money than upgrading to triple.
Conservation Areas and Listed Buildings
If you live in a conservation area, replacing windows can be more complicated. Most conservation areas require you to replace like for like in terms of style and material, which typically means timber. Even if uPVC is technically permitted, local planning guidance often strongly discourages it and some councils require pre approval.
Listed buildings require listed building consent for window replacements. This is separate from planning permission and applies even to internal works. Always consult your local planning authority before ordering windows for a listed property.
Finding a Good Window Installer
The window industry has historically had problems with high pressure sales tactics and inflated pricing from large national companies. Here is how to navigate it sensibly.
- Get three or more quotes. Prices vary enormously. The difference between the cheapest and most expensive quote for identical windows can easily be 50 percent.
- Check FENSA or CERTASS registration. All replacement window installers should be registered with FENSA or CERTASS. These schemes certify that the installer can self certify that the work complies with building regulations, saving you from having to apply for building regulations approval separately. Registration is free to check on their websites.
- Ask about the manufacturing origin. Windows made in the UK to British standards are generally higher quality than imported units. The frame profile (Rehau, Deceuninck, VEKA for uPVC; Schuco, Alumasc, Smart Systems for aluminium) gives you an indication of quality.
- Check warranty terms. Reputable companies offer 10 year guarantees on both the product and installation. Avoid companies that offer very short warranties or hide behind the manufacturer warranty.
- Do not let salespeople pressure you. Any company that requires a decision on the day or offers a discount that expires immediately is using pressure sales tactics. Walk away.
Are There Any Grants or Funding Available?
The UK government has run various schemes to help fund energy efficient home improvements, but availability changes regularly. As of 2026, the main routes to potential funding are:
- ECO4 scheme: The Energy Company Obligation scheme provides free or subsidised energy improvements for households on certain benefits or with low incomes. Windows may qualify depending on the property's energy performance. Contact your energy supplier to check eligibility.
- Great British Insulation Scheme: Focused primarily on insulation but has included glazing in some circumstances for eligible households.
- Local authority grants: Some councils offer supplementary funding for energy improvements in their area, particularly for older housing stock. Check your council's website for current schemes.
For most homeowners, there is currently no universal grant available for window replacement. Check the government's Simple Energy Advice service for the most current information on what you might qualify for.
Frequently Asked Questions
How much does it cost to replace windows in the UK?
A single standard casement window replacement costs £400 to £900 installed for uPVC double glazing. Replacing all windows in a 3 bed semi costs £3,500 to £7,000 depending on the number of windows and material choice.
How much does a uPVC window cost?
A uPVC casement window costs £150 to £400 for supply only and £400 to £900 installed including removal of the old window. It is the most affordable and most common window material in the UK.
How much do aluminium windows cost?
Aluminium windows cost £500 to £1,500 per window installed. They are around 40 to 60 percent more expensive than uPVC but offer slimmer sightlines and a longer lifespan.
How much do sash windows cost to replace?
Replacing a sash window costs £800 to £2,000 installed for uPVC sliding sash. Timber sash windows cost £1,000 to £3,000 per window. Conservation area requirements may mean timber is the only option.
Is it worth getting triple glazing instead of double?
For most UK homes, the payback period on triple glazing makes it hard to justify purely on energy savings. It makes more sense for very exposed properties, homes with specific energy performance targets, or where noise reduction is a priority.
How long does window replacement take?
A single window replacement takes 1 to 3 hours. Full house replacement in a 3 bed semi typically takes 1 to 2 days, done one window at a time so the property is never left exposed. Lead times from order to installation are usually 4 to 8 weeks.
Do I need planning permission to replace windows?
Most window replacements are permitted development and do not require planning permission. Conservation areas and listed buildings are exceptions. Always check with your local planning authority before ordering.
What is the cheapest way to replace windows in the UK?
Standard uPVC casement double glazing from a local installer with FENSA or CERTASS registration is the most cost effective option. Get at least three quotes and avoid national glazing companies with commission based salespeople, whose prices are often 30 to 50 percent higher for equivalent products.
Also see our guides on how much a new boiler costs and how much an electrician costs in the UK.