A 4 kW solar system on a south-facing roof in the Midlands. £6,500 installed. £600 saved in year one. Paid for itself by 2034. That's the short version, and for roughly 60% of UK homeowners, the maths work out similarly.
But "worth it" depends on your roof, your usage, and how long you plan to stay in your home. We've run the numbers for different scenarios so you can see where you'd land.
The Payback Maths
Let's start with the calculation that actually matters. A typical 4 kW system in England generates around 3,400 kWh of electricity per year, according to Energy Saving Trust data. How much that saves you depends on two things: how much you use directly (self-consumption) and what your electricity supplier pays for the surplus (the Smart Export Guarantee rate).
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Self-consumption rate: 40% (typical for a household out during the day)
Electricity price: 24p per kWh (Ofgem price cap, April 2026)
SEG export rate: 8p per kWh (mid-range across suppliers)
Annual saving: 1,360 kWh used directly x 24p = £326. Plus 2,040 kWh exported x 8p = £163. Total: roughly £490 per year.
Payback period: about 13 years. Not bad, but not spectacular.
Now here's where it gets interesting. Bump self-consumption to 60% (by running the washing machine and dishwasher during the day, or adding a timer to your immersion heater) and the numbers shift.
Higher self-consumption: 2,040 kWh used directly x 24p = £490. Plus 1,360 kWh exported x 8p = £109. Total: roughly £599 per year. Payback: about 11 years.
Add a battery and push self-consumption to 80%? Annual benefit climbs to £700 to £800. But the battery adds £4,000 to £5,000 to the upfront cost, so the combined payback stays around 10 to 12 years. See our solar battery storage guide for the full breakdown on whether a battery makes sense for your situation.
The honest takeaway: solar panels are a solid long-term investment, not a get-rich-quick scheme. You're looking at 8 to 13 years to break even depending on your self-consumption, then 12 to 22 years of essentially free electricity. Panels typically last 25 to 30 years with minimal maintenance.
When Solar Panels Are NOT Worth It
Here's what most guides won't tell you. Solar panels aren't a universal win. There are specific situations where the numbers don't stack up.
North-facing roof
A north-facing roof in the UK generates roughly 50% to 60% less electricity than a south-facing one, according to Energy Saving Trust orientation data. That turns a 13-year payback into a 20-year-plus payback. East and west-facing roofs are fine, losing only about 15% to 20% compared to south. But pure north? The maths rarely work.
Heavy shading
Trees, neighbouring buildings, chimneys casting shadows across your panels for several hours a day can cut output by 20% to 50%. Modern panels with optimisers handle partial shading better than older string systems, but significant shading still kills the business case. Ask any installer for a shading analysis before committing.
Planning to move within 5 years
Solar panels add value to a property, roughly £5,000 to £8,000 according to research from the Department for Energy Security and Net Zero. But you won't recoup the full installation cost in the sale price if you move before the payback period. If you're planning to sell within 5 years, the financial case is weaker.
Very low electricity use
A single person in a small flat using 1,500 kWh per year won't save enough to justify the installation cost. Solar works best for households using 3,000 kWh or more annually, where there's enough consumption to absorb the generation.
Listed building or conservation area
You might need planning permission, which can be refused. Check with your local planning authority before getting quotes. Standard permitted development rights for solar panels don't apply to listed buildings.
With and Without a Battery
The battery question comes up in every solar conversation. Here's the quick version.
Without a battery, you use solar electricity as it's generated and export the rest. Self-consumption typically sits at 30% to 50% depending on whether anyone's home during the day.
With a battery, you store surplus daytime generation and use it in the evening. Self-consumption jumps to 60% to 80%. The extra savings are real, typically £200 to £400 per year, but the battery costs £3,000 to £7,000.
So does the battery pay for itself? It depends on your usage pattern. If you're out all day and have high evening consumption (especially an EV), a battery can pay back in 8 to 12 years. If you're home during the day and already self-consuming most of your generation, the payback stretches beyond 15 years.
Our advice: install solar first, live with it for 6 months, check your export data, then decide on a battery. You can always add one later. If you do go ahead, our battery storage guide covers costs, types, and the best models for UK homes.
The SEG Bonus
The Smart Export Guarantee puts money back in your pocket for every unit of surplus electricity you send to the grid. It's not going to make you rich, but it chips away at the payback period.
Rates vary wildly by supplier. As of April 2026, Ofgem data shows rates from 3p to 15p per kWh. Octopus Energy's Outgoing tariff sits at the top end. Some suppliers offer time-of-use export rates that pay more during peak demand.
For a 4 kW system exporting 50% of its generation, SEG payments add £100 to £300 per year depending on your tariff. You're not locked into your electricity supplier for SEG, so shop around.
Right, so what about grants? The main financial support for solar in 2026 is the 0% VAT relief (saving £1,000 to £1,500 on a typical system) and the SEG. If you're on a lower income and receive certain benefits, ECO4 could fund your entire installation. Our full guide on solar panel grants covers every scheme currently running.
The 25-Year View
Solar panels are a long game. Here's what the numbers look like over the full lifespan of a system.
A £6,500 system saving £550 per year (mid-range estimate) returns £13,750 over 25 years. That's a net gain of £7,250, or a return of roughly 112% on your investment. And that assumes electricity prices stay flat, which they almost certainly won't. Every 1p increase in the electricity price adds roughly £34 per year to your savings.
Panels degrade slowly, losing about 0.5% efficiency per year according to MCS performance data. After 25 years, they're still producing around 87% of their original output. Many systems continue working well beyond 30 years.
Inverters typically need replacing once during the panel lifespan, at a cost of £800 to £1,500 after 10 to 15 years. Factor that into your calculations.
For current pricing by system size and region, check our detailed guide on solar panel costs. And if you're weighing solar against a heat pump, our solar vs heat pumps comparison covers that decision.
Want to see what grants apply to your home? Open the eligibility checker. Two minutes, and you'll know exactly where you stand.
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Frequently asked questions
Do solar panels work in winter in the UK?
Yes, but they produce less. A typical system generates about 10% to 15% of its annual output during December and January, rising to peak production in May to July. You'll still offset some electricity use in winter, but the real savings come from the longer, sunnier months.
Do solar panels increase house value?
Research from the Department for Energy Security and Net Zero suggests solar panels add roughly £5,000 to £8,000 to a property's value. Buyers increasingly see them as a positive feature, especially with high electricity prices. The key is having a transferable warranty and MCS certification documentation.
How long do solar panels last?
Most solar panels are warranted for 25 years and continue producing electricity well beyond that. Degradation is slow, about 0.5% per year, so after 25 years your panels still produce around 87% of their original output. The inverter typically needs replacing once, after 10 to 15 years, at a cost of £800 to £1,500.
Can I install solar panels myself?
You can, but you'll lose access to the Smart Export Guarantee (which requires MCS certification), the 0% VAT relief, and any grant eligibility. DIY installations also void most panel warranties and may cause issues with your home insurance. For the vast majority of homeowners, professional MCS-certified installation is the only sensible route.
What happens to solar panels when there's a power cut?
Standard grid-tied solar systems shut down during a power cut for safety reasons, to prevent feeding electricity into lines that engineers may be working on. If you want backup power during outages, you need a battery with an Emergency Power Supply (EPS) function. Not all batteries offer this, so check before buying.