- Sunshine on the best roofs
- 1,181 h/yr
- Yield (south-facing)
- 1,176 kWh/kWp
- 4 kWp system makes
- 4,704 kWh/yr
- Payback
- 7.2 years
How much sun Cornwall gets
Cornwall is the sunniest of the 15 counties we cover: the best-placed roofs we sampled around Truro get 1,181 sunshine hours a year.
A 4 kWp system here makes about 904 kWh a year more than the same system in Northumberland (24% more), which shortens the payback.
What a 4 kWp system is worth here
On a south-facing roof in Cornwall, a 4 kWp system (around nine panels) would cost about £5,600 and save roughly £714 in its first year for a typical three-bed home on a 27p/kWh tariff, including £445 from exporting spare power at 12p/kWh. With energy prices rising 3% a year, that pays back in about 7.2 years.
Install costs use the calculator's national range: there's no reliable published breakdown of solar install prices by county.
Connecting to the grid in Cornwall
Your network operator here is National Grid Electricity Distribution (South West). Most home systems fit within G98: your installer notifies National Grid Electricity Distribution within 28 days of switching on. Larger systems (above 16 A per phase, about 3.68 kW on a single-phase supply) need a G99 application approved before installation — allow extra weeks for that.
Grants and schemes in England
The Smart Export Guarantee (SEG) requires larger electricity suppliers to offer a tariff for exported solar power from MCS-certified installs. The rate is set by each supplier, so it's worth comparing.
Boiler Upgrade Scheme
£7,500 off an air source or ground source heat pump that replaces fossil-fuel heating. Your MCS-certified installer applies for it.
Confirm with: Your MCS installer; Ofgem administers the scheme.
Warm Homes: Local Grant
Council-delivered upgrades (which can include solar PV and heat pumps) for lower-income households in England.
Confirm with: Your local council — availability varies by area.
- 0% VAT on solar panels, batteries and heat pumps until 31 March 2027 — install prices in the calculator already assume it.
Scheme notes last checked 2026-09-23.
Where these numbers come from
We sampled 5 real roofs around Truro with Google's Solar API (imagery 2020, sampled 2026-09-23) and took the sunshine on the second-best-placed roof — a well-oriented, unshaded roof, without letting one odd reading set the figure. The yield scales the calculator's national 950 kWh/kWp by how that compares with the middle of the first 15 counties we sampled. Your own roof's direction, pitch and shading will move it either way.
- Google had data for 5 of the 9 points we tried around Truro, so this figure rests on fewer roofs than most.
- The aerial imagery here is Google's medium-resolution tier, so roof-by-roof detail is coarser than in the cities.
- Some imagery dates from 2020; roofs or nearby trees may have changed since.