- Sunshine on the best roofs
- 1,023 h/yr
- Yield (south-facing)
- 1,019 kWh/kWp
- 4 kWp system makes
- 4,076 kWh/yr
- Payback
- 8.1 years
How much sun Cardiff gets
Cardiff ranks 6th of the 15 counties we cover for sunshine, between Devon and Leicestershire.
A 4 kWp system here makes about 276 kWh a year more than the same system in Northumberland (7% more), which shortens the payback.
What a 4 kWp system is worth here
On a south-facing roof in Cardiff, a 4 kWp system (around nine panels) would cost about £5,600 and save roughly £634 in its first year for a typical three-bed home on a 27p/kWh tariff, including £373 from exporting spare power at 12p/kWh. With energy prices rising 3% a year, that pays back in about 8.1 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 Cardiff
Your network operator here is National Grid Electricity Distribution (South Wales). 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 Wales
The Smart Export Guarantee (SEG) applies in Wales: larger suppliers must offer an export tariff for MCS-certified installs, at a rate each supplier sets.
Boiler Upgrade Scheme
£7,500 off an air source or ground source heat pump — the scheme covers Wales as well as England.
Confirm with: Your MCS installer; Ofgem administers the scheme.
Warm Homes Nest
Welsh Government scheme offering free home energy improvements to eligible lower-income households. The current scheme contract runs from 1 April 2024 to 1 April 2031.
Confirm with: The Nest scheme (Welsh Government) — eligibility is means-tested.
Source: Contract dates: British Gas contract award announcement, April 2024
- 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 8 real roofs around Cardiff with Google's Solar API (imagery 2022–2025, 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.