Cardiff is one of the stronger cities for solar in our dataset. PVGIS, the European Commission’s free solar model, estimates 1,042 kWh per kWp a year for a south-facing roof at 35 degrees. That is about 2% above London at 1,019 kWh per kWp, and 17% above Aberdeen at 893 kWh per kWp.

Since Solar Yield is an independent estimator, not an installer, this page shows what those figures mean for a Cardiff home.

What a typical Cardiff system could produce

Annual output scales with system size. A 4 kWp system could generate about 4,168 kWh a year in Cardiff. A 4.5 kWp system could reach about 4,689 kWh.

Ofgem’s medium household uses 2,500 kWh of electricity a year on a standard meter, according to its typical consumption values. Over a year, a 4 kWp roof in Cardiff can therefore out-produce that figure. Even so, summer output cannot fill winter demand unless you store it.

Our guide on how much electricity a 4kW system generates explains the arithmetic behind these numbers.

Best month and worst month

May is the strongest month in Cardiff at 132.5 kWh per kWp, while December is the weakest at 32.3 kWh per kWp. The best month therefore produces about 4.1 times the worst. May, June and July together give 392.8 kWh per kWp.

In contrast, November, December and January together give only 111.5 kWh per kWp. Our post on solar panel output in winter explains what to expect from those months.

Tilt and direction

PVGIS puts the optimal tilt for Cardiff at 39 degrees, with 1,044 kWh per kWp a year. A 35 degree roof gives 1,042 kWh per kWp. The difference is small enough to ignore on most roofs.

Direction matters more. Energy Saving Trust says east or west facing systems tend to produce 15% to 20% less than south facing ones.

Planning rules and City of Cardiff Council

Although Wales sets its own planning rules, the core limit matches England’s. According to the Welsh Government, roof solar on a single house is usually permitted development. Panels should project no more than 200 mm and must not go above the ridgeline. They also need siting to limit the effect on the building’s appearance.

However, listed buildings need planning permission and listed building consent. In conservation areas, panels on principal or side walls visible from the highway need permission. City of Cardiff Council is the local planning authority, and local Article 4 directions can remove rights. Check the Welsh Government page and ask the council before you commit.

Grid connection under National Grid Electricity Distribution

Your network operator depends on your postcode. In Cardiff it is usually National Grid Electricity Distribution. Under G98, a type-tested system up to 16 A per phase connects first. That is about 3.68 kW on a single-phase supply, and the installer tells the operator within 28 days.

Because larger systems fall under G99, the installer must apply and get approval before installing. MCS explains both routes on its notifying network operators page.

Cost, support and quotes

DESNZ puts the 2025 to 2026 median installed cost at about £1,595 per kW for systems up to 4 kW. A 4 kWp system therefore costs about £6,400, according to the DESNZ cost data. The Smart Export Guarantee applies in Wales, and Energy Saving Trust says exported units typically earn around 12p each.

We found no current Welsh Government grant for domestic solar, but that is not proof none exists. Check gov.wales and your council. Our pages on solar panel installation and solar battery storage explain how referrals work.

Sizing is the next question, since output depends on panel count. Our upcoming guide on how many solar panels you need turns your usage into a system size. For comparison, see the solar output figures for Swansea and the Bristol solar installation page.

Next steps

Start with the solar yield calculator to test your roof. Then use get quotes to send one enquiry to MCS-certified installers. Solar Yield passes on your request and does not install anything itself.