On a pure cash return, solar panels win: a typical domestic system pays for itself in around 9 years and keeps earning after that. Double glazing does not compete on that measure, and it is not meant to. It cuts heat loss and, more importantly, delivers a warmer, quieter home with less condensation, and it becomes necessary when your existing units have failed. The honest summary is that these two upgrades solve different problems: solar for a defined financial return, glazing for comfort and for when the old windows need replacing anyway. To keep the two sides consistent, we point you to our own energy savings calculator for the glazing figure rather than importing an outside number.
The headline comparison
The table below sets the two upgrades side by side. The solar figures are the Energy Saving Trust's current numbers for a typical domestic system. For glazing we deliberately point to our own calculator rather than a third-party saving, so the glazing side matches the rest of this site instead of a competing estimate.
| Solar panels (PV) | Double glazing | |
|---|---|---|
| Typical system or job | About 4.5 kWp | Whole-house uPVC |
| Typical cost | £6,100 | From £6,500 (mid-terrace) |
| Annual benefit | About £750 a year (incl. SEG export) | Modelled per home in our calculator |
| Simple payback on bills | Around 9 years | Long on bills alone |
| What it actually does | Generates electricity | Cuts heat loss, noise and condensation |
Sources: Energy Saving Trust (solar PV: about 4.5 kWp, £6,100, £750 a year including SEG export, roughly 9-year payback, figures current as of 2026); DGCC 2026 dataset (whole-house glazing cost). Glazing saving is modelled per home in the energy savings calculator.
Solar: a defined cash payback
Solar is the clear winner if you are judging purely on money. According to the Energy Saving Trust, a typical domestic system is about 4.5 kWp, costs around £6,100 to install, and saves about £750 a year once you include the Smart Export Guarantee (SEG) earnings from the electricity you sell back to the grid. That is a payback of roughly 9 years, after which the savings keep coming for the rest of the system's life. It is a genuine investment with a return you can put a date on, which is something double glazing simply cannot match on bills.
Best Buy Solar for a defined cash return, with a payback of around 9 years and earnings that continue afterwards.
Double glazing: comfort, not just cash
Double glazing plays a different game. Its saving on bills is real but modest, and the payback on energy alone is long, which is why we never sell windows on the promise of a fast return. What glazing does deliver from day one is a warmer, draught-free room, less outside noise, and an end to the cold inner pane that drives condensation, mould and rotten frames. Because the bill saving depends heavily on your current windows, house size and region, the fair way to size it is to model your own home in the energy savings calculator rather than lean on a single headline figure. Our is double glazing worth it guide works through that comfort-and-resale case in full.
Worth it Glazing is worth it for comfort, quiet and condensation control, and when the existing units are failing, not for a fast cash payback.
They solve different problems
The reason this is not a straight fight is that the two upgrades do not overlap. Solar generates electricity and pays you back in cash. Glazing stops heat escaping and makes the home nicer to live in, and it is usually driven by the windows needing replacement anyway rather than by a spreadsheet. Comparing their paybacks head to head misses the point: one is an energy generator, the other is a fabric and comfort upgrade that happens to save a little on heating. If you want to see how glazing stacks up against the cheaper fabric measures on payback, our glazing or insulation first guide covers that order.
It depends Which gives the better return depends on what you are buying: cash generation or a warmer, quieter home.
Which should you do first?
The tie-breaker is usually the state of your windows. If they are misted, blown or draughty, replacing them is a maintenance job that has to happen whatever the cash return, so the windows come first. If your windows are sound and you mainly want a defined return on your money, solar is the stronger financial play and can go ahead while the windows keep serving. Budget and roof suitability matter too, but the honest rule of thumb is simple: solve failing windows when they fail, and add solar for the cash return when the roof and finances suit. The choice of glass on those windows still matters for comfort, so our single vs double vs triple glazing guide can help you spec them.
People ask me to choose between solar and new windows as if it is one or the other. It rarely is. If your units have blown, you are replacing those windows no matter what the solar maths says. And if your windows are fine and you want your money to work, solar has the clearer payback. I have both on my own house, for different reasons.
Tom Bradley, FENSA-registered installer
The verdict
Solar for cash return, glazing for a warmer, quieter home and for when the old units have failed. On a pure financial measure solar is the Best Buy, with a typical system at about 4.5 kWp, around £6,100 to install, roughly £750 a year saved including SEG export and a payback near 9 years. Double glazing is Worth It for what it does that solar cannot, delivering comfort, quiet and condensation control and stepping to the front of the queue whenever your units are failing. For most homes it is not either-or over time: replace failing windows when they need it, model your bill saving in the energy savings calculator, and add solar when the roof and budget suit for the defined financial return.
Frequently asked questions
For a pure cash return, solar wins. A typical domestic system of about 4.5 kWp costs around £6,100 and saves about £750 a year including SEG export earnings, giving a payback of roughly 9 years (Energy Saving Trust). Double glazing rarely pays back on bills alone; its value is comfort, quiet, condensation control and replacing failing windows. They solve different problems.
The Energy Saving Trust puts a typical domestic system at about 4.5 kWp, costing around £6,100 to install and saving about £750 a year once you include Smart Export Guarantee (SEG) earnings from the electricity you sell back. That works out at a payback of around 9 years, after which the savings are effectively free for the rest of the system life.
Not in the same way. Solar has a defined cash payback because it generates and exports electricity. Double glazing cuts heat loss, but its payback on bills alone is long, so it is usually justified by comfort, noise and condensation and by the windows needing replacement anyway. Model the bill saving for your own home in the energy savings calculator rather than assuming a fixed figure.
It depends on the state of your windows. If they are misted, draughty or failing, replace them first because that is a maintenance job whatever the cash return. If your windows are sound and you mainly want a defined return on your money, solar is the stronger financial play. For many homes it is not either-or over time.
Yes, and they complement each other. Solar generates electricity and delivers a cash payback; double glazing keeps that heat in and makes the home warmer and quieter. Prioritise by what is failing and by your budget: replace failing windows when they need it, and add solar for the defined financial return.