22.3 gigawatts. That is the UK’s total installed solar capacity as of early 2025, enough to power roughly 8 million homes at peak output. The figure, reported by pv magazine Global, marks a 50% increase since 2021, when the total stood at 14.6 GW. But the headline number is less interesting than what it means for the cost of a single panel on a single roof.
As reported by pv magazine Global, the cost per kilowatt of installed solar has fallen as supply chains stabilise and installers scale up. For UK homeowners, that translates into a concrete number: a typical 4 kW system now costs between £5,000 and £6,500 fully installed, according to Energy Saving Trust estimates. Two years ago, the same system would have set you back £7,000 to £8,000.
Who benefits, and who doesn’t
Not every roof is a good candidate. South-facing pitches with little shading and a roof age under 15 years are ideal. East-west arrays work too, but produce about 15% less annual output. Ofgem data shows the average UK home uses 2,900 kWh of electricity a year. A 4 kW system in southern England generates around 3,400 kWh annually, enough to cover most daytime use and export the surplus.
The catch is timing. Most households are out during the day when panels produce most. Without a battery, typically £1,500-£3,000 extra, you export roughly half your generation to the grid at the Smart Export Guarantee rate of around 15p/kWh. With a battery, you store daytime power for evening use, effectively doubling the bill savings. The payback period stretches from 10 years without a battery to 12-14 years with one, though rising electricity prices shorten both.
EPC impact, the hidden value
Solar panels alone won’t lift a home from an EPC band E to a C. But they add up to 5 points under the current methodology, enough to move a D to a C or a C to a B. For landlords, that is important: from 2028, all new tenancies in England and Wales will require an EPC rating of C or above. A 4 kW system, combined with loft insulation and a modern boiler, can push a marginal D-rated property into compliance.
The government’s 0% VAT on solar installations, introduced in 2022 and extended to 2027, saves roughly £1,000 on a typical system. The Boiler Upgrade Scheme does not cover solar, but the Home Upgrade Grant (for low-income households off the gas grid) does. Most homeowners will rely on self-financing or a green mortgage product from lenders like Nationwide or Barclays, which offer preferential rates for energy-efficient homes.
What to do next, and by when
The falling cost per kW is not a reason to wait. Panel prices are low partly because of a global oversupply of Chinese modules, which could tighten if trade tensions escalate. The 0% VAT window closes in March 2027. And the longer you delay, the more months of £200-£400 annual savings you lose.
Start with a free survey from a certified Microgeneration Certification Scheme (MCS) installer. Ask for a quote broken down by panels, inverter, scaffolding, and labour. Compare at least three quotes. Check your roof orientation on Google Maps or a solar calculator. If the numbers work, and for most south-facing roofs in the south and Midlands, they do, book installation before the autumn scaffolding slots fill up.
Frequently Asked Questions
A typical 4 kW system costs between £5,000 and £6,500 installed, including panels, inverter, scaffolding, and labour. Prices have fallen roughly 20% since 2023 due to lower panel costs and increased competition among installers. A battery adds £1,500-£3,000. VAT is 0% until 2027.
Yes, typically by 3 to 5 points under the current EPC methodology. This can move a property from band D to C, which is important for landlords facing the 2028 minimum C-rating requirement. The improvement is lower if your home already has high-efficiency heating or is very well insulated.
