Whether solar panels are worth it does not have one answer, because it depends on your roof, your habits and the prices of the day. But it does have a clear set of factors and, in 2026, some firm enough figures to put real numbers on the decision. Run your own situation through them honestly and you can judge a quote without leaning on the salesperson's optimism. The how-it-works detail sits in the solar basics guide; this one is about the money.
The short answer. A typical 4 kW system costs around £7,000 to £8,500 fully installed in 2026, with no VAT, and generates roughly 3,400 to 4,000 kWh a year on a well-sited roof. Between the electricity you avoid buying at the roughly 26p cap rate and what you earn exporting the rest at a 5p to 15p export rate, a good system returns somewhere around £650 to £820 a year, paying back in roughly 9 to 12 years and then generating largely free power for many years more. A poor roof, heavy shade or a low export rate stretch that out.
The roof comes first
No amount of clever financing rescues a poor roof. A south-facing, unshaded roof at a reasonable pitch is the strong case; east and west roofs still work but generate less; a north-facing or heavily shaded roof rarely justifies the cost. Shading is a particular killer, because even partial shade across part of the array at the wrong time of day can drag the output down disproportionately. Before anything else, be honest about which way your roof faces and what shades it through the day. If the roof is wrong, the rest of the sums do not matter.
What it costs and what it generates
A standard domestic system is around 4 kilowatts, roughly ten panels, and in 2026 costs about £7,000 to £8,500 fully installed, including the panels, inverter, mounting and electrical work, with residential solar carrying no VAT. On a well-sited roof that system generates somewhere around 3,400 to 4,000 kWh a year, concentrated in the brighter half of the year, with an east or west roof or any shading pulling the figure down. Those two numbers, the cost and the yearly generation, are the foundation of every payback sum, so be wary of a quote that is vague about either or that predicts generation well above the range for your orientation.
Where the value comes from: self-use versus export
Every unit your panels make is worth one of two things. If you use it in the house there and then, it saves you buying that unit from the grid, currently about 26p under the price cap. If you do not, it is exported and earns you the export rate instead. Power you use yourself is therefore worth more than power you export, but how much more depends on your export rate. On a low 5p export deal, self-used power is worth roughly five times as much, so self-consumption is everything. On one of the better 15p export deals now available, the gap narrows to under double, so exporting is far less of a loss than it used to be. Either way, the return rises the more of your own generation you consume, which is why a household with someone home in the day, or willing to shift the washing, dishwasher, hot water and car charging into daylight, gets more from the same panels than one that exports most of its midday output to an empty house.
Export rates in 2026, and the moving goalposts
You are paid for exported electricity through the Smart Export Guarantee, and the rates vary a great deal between suppliers. In 2026 flat export rates run from around 5p per kWh at the bottom to about 15p at the best, with a couple of deals near 16p that require you to also buy your electricity from the same supplier. Households with a battery can access time-of-use export tariffs that pay much more during peak evening windows, sometimes over 30p per kWh, though those need both a battery and that supplier's import tariff. Because these rates change and the price of the grid electricity you displace changes too, treat any single confident payback figure in a sales pitch with caution, and ask what export rate and what import price it assumed.
The payback, worked out
Put the numbers together for an example 4 kW system costing £7,500 and generating 3,600 kWh a year, displacing electricity at 26p and exporting the surplus at a 15p rate. The result depends heavily on how much you use yourself.
| Self-consumption | Saved on bills | Export earnings | Total per year | Payback |
|---|---|---|---|---|
| 30% used at home | ~£281 | ~£378 | ~£660 | ~11 years |
| 50% used at home | ~£468 | ~£270 | ~£740 | ~10 years |
| 70% used at home | ~£655 | ~£162 | ~£820 | ~9 years |
Example only: 4 kW system at £7,500, 3,600 kWh a year, 26p import, 15p export, mid 2026. On a low 5p export rate the totals fall and the gap between low and high self-consumption widens sharply, pushing a low user past fifteen years while a high user stays around ten. Your roof, prices and habits move all of these.
Where batteries fit
A battery stores your surplus midday generation for use in the evening, lifting self-consumption and the value of the system, especially for households out all day, and it gives you access to the higher peak export tariffs mentioned above. The catch is the cost, typically several thousand pounds on top, so a battery improves the usefulness of solar while often lengthening the overall payback rather than shortening it. Whether to add one is a separate calculation, not an automatic yes. For some homes it transforms the case; for others, at today's better export rates, it is a costly extra the export payments would have covered more cheaply.
The honest long-term picture
A well-sited system with decent self-consumption pays for itself in roughly nine to twelve years at current prices and then generates largely free power for many years beyond, since panels last well over two decades. It is a long-term investment, closer to overpaying your mortgage than to a quick win, and it competes for your money with the cheaper efficiency jobs that pay back far faster. The sensible order is to do the insulation, draught-proofing and heating basics first, since they cost less and return sooner, and then consider solar as the larger, slower-burn step once the easy savings are banked.
Questions to ask before you sign
When you get a quote, ask what generation it predicts for your specific roof orientation and shading, not a generic figure; what self-consumption rate it assumes and why; what electricity price and export rate underpin the payback; whether a battery is included and what the sums look like without it; and what warranties cover the panels and, separately, the inverter, which is the component most likely to need replacing within the system's life. A reputable installer answers these plainly. Vague, pressured or too-good-to-be-true answers are the signal to walk away and get another quote.
The bottom line
In 2026 a well-sited 4 kW system costs around £7,000 to £8,500, generates 3,400 to 4,000 kWh a year, and returns roughly £650 to £820 of saved and earned money, paying back in about nine to twelve years before decades of nearly free power. The case is strongest on a good south-facing roof for a household that uses plenty of its own generation, and weakest on a poor or shaded roof or a low export rate. Do the cheap efficiency jobs first, get two or three honest quotes, and judge them on real generation and price assumptions rather than a single glossy payback number.