The average Wiltshire rooftop will generate 15% more electricity this year than the same panels in Manchester. That is not a guess, it is the finding of a new analysis by solar installer Rayo, as reported by Rayo. For a homeowner in Salisbury, that difference is worth roughly £150 a year on a typical 4 kWp system. For a homeowner in Stockport, it is money left on the roof.
Why Wiltshire pulls ahead
The county sits in a sweet spot of southern England, high solar irradiance, low average cloud cover, and relatively few tall buildings or hills that cast shade. Rayo’s data puts Wiltshire second only to Cornwall for annual solar production per installed kilowatt-peak. That matters because the UK’s solar resource varies by up to 30% between the sunniest and cloudiest postcodes. Ofgem’s latest figures show that a typical 4 kWp system in the South West generates around 3,800 kWh per year. The same array in the North West struggles to reach 3,200 kWh. For a household on a standard variable tariff paying 24.5p per kWh, that is a gap of £147 a year, every year for 25 years.
What it costs a typical 3-bed semi
The Energy Saving Trust estimates that a 4 kWp system costs between £5,000 and £8,000 installed, depending on roof type and scaffolding access. In Wiltshire, that outlay is recouped in roughly nine years through electricity bill savings and the Smart Export Guarantee (SEG) payments of around 15p per kWh exported. In a cloudier county, the payback stretches to 12 or 13 years. The catch is that most solar calculators assume a national average. A homeowner in Wiltshire who uses a generic tool will underestimate their savings by about 20%. The same applies to EPC ratings: a well-sited Wiltshire system can lift a D-rated home to a C, whereas a shaded northern installation might only nudge it to a D+.
What this misses
Rayo’s ranking is based on theoretical production, not every roof in Wiltshire faces south at 30 degrees. A north-facing roof in Chippenham will underperform a south-facing one in Aberdeen. The real variables are county, orientation, pitch, and local shading from trees or neighbouring buildings. Homeowners should get a site-specific survey before committing. The government’s Boiler Upgrade Scheme and the new Great British Insulation Scheme are location-blind, they do not pay more for a sunnier postcode. But the SEG rates vary by supplier: Octopus pays 15p per kWh exported, while EDF pays 5p. A Wiltshire homeowner exporting 2,000 kWh a year could earn £200 more with Octopus than EDF, a difference worth checking before signing a contract.
What to do and by when
If you are in a high-solar county like Wiltshire, Cornwall, or Dorset, the case for panels is stronger than the national averages suggest. Use a local installer who supplies generation estimates based on your specific roof, not a UK mean. Check your current electricity tariff and SEG export rate, switching to a higher-paying supplier can add £100–£200 a year. The VAT on solar panels is zero until 2027 under the government’s temporary relief. Households considering a heat pump should also know that solar panels can power it for free on sunny days, cutting annual heating costs by up to £400. The window for the best returns is now: energy prices are forecast to stay above 24p per kWh through 2026, and grant schemes are finite.
Frequently Asked Questions
No. Even in lower-irradiance areas, a well-sited system can save £400–£600 a year on electricity bills. The payback period is longer, typically 12–15 years, but panels last 25+ years, so you still come out ahead. The key is to use a local installer who can model your roof's exact generation, not a national average.
The SEG requires licensed suppliers to pay households for excess electricity exported to the grid. Rates vary: Octopus Energy offers around 15p/kWh, while EDF pays 5p. Check comparison sites like Ofgem's approved list or the Energy Saving Trust's tariff checker. You can switch supplier without changing your solar setup.
