Solar yield in Wales

Solar yield means the electricity your panels make in a year. In Wales it varies by place, by roof direction and by shade. Therefore a design built for your own roof matters more than a national stereotype about the weather.

This guide uses PVGIS, the European Commission’s free solar tool, to show what to expect. Because Solar Cymru is an independent guide, treat these as planning figures rather than promises. You can run PVGIS yourself for any address.

What a Welsh roof can make

We ran PVGIS for each town we cover in October 2026. The runs assumed crystalline silicon panels, 1 kWp of capacity, 14% system losses and a fixed roof mount. A south-facing roof at 35 degrees makes roughly 810 to 1,070 kWh a year for each kWp across those towns. A 4 kWp system therefore makes roughly 3,200 to 4,300 kWh a year.

The Energy Saving Trust describes a typical home system as about 4.5 kWp. Our post on how many solar panels you need shows how to match a system to your use.

Place to place

Barry tops our runs at about 1,070 kWh per kWp. Holyhead makes about 1,050, Cardiff about 1,040 and Newport about 1,030. Swansea comes in at about 1,010, while Wrexham makes about 970.

Hills lower the figure in PVGIS’s terrain model. For that reason, Bangor shows about 810 and Ebbw Vale about 930. A run for your own address is more reliable than a town average.

For example, our page on solar installers in Cardiff shows a southern city figure. Meanwhile, our page on solar panels around Wrexham shows a northern one.

Roof direction and pitch

Direction changes output, although less than many people expect. Roofs facing east or west make about 15 to 20% less than a south-facing roof. South-east and south-west roofs make about 95% of south output. In contrast, a north-facing roof makes only 53 to 59% of south output, so the Energy Saving Trust does not recommend one.

An east-west layout trades peak output for a wider generation window. Our post on solar on east-west and north-facing roofs explains when that suits a household.

Pitch matters little. For instance, at Cardiff a 15 degree south roof makes 976 kWh per kWp and a 60 degree roof makes 993. A 35 degree roof makes 1,042, while a vertical south wall makes 745.

Shade

Topography, trees, chimneys and neighbouring buildings can all matter. The assessment should model the timing and electrical impact of shade, not label the roof sunny or shaded. In particular, MCS requires the performance estimate to state a shade factor.

Power optimisers or microinverters can limit the loss when part of the array is shaded. However, they add nothing on a roof with no shade. Ask the installer to explain why they chose their equipment.

Welsh weather

Weather is a common worry in Wales. The PVGIS figures above already use satellite radiation data for each place. Our post on whether solar panels work in Welsh weather goes through the evidence.

Rain also helps, because it cleans panels tilted at 15 degrees or more. Ground-mounted or dusty sites may need occasional cleaning. Our post on solar panel maintenance in a wet climate lists the checks.

Do not use the old rule of thumb

You may see a rule of thumb of 750 kWh per kWp. It comes from a 2016 Welsh Government research report. Current PVGIS values for Wales are higher, so that figure is out of date. A claim far above our ranges also deserves a question, since it needs a reason.

From yield to money

More output does not always mean faster payback, because use matters too. The Energy Saving Trust estimates payback in Aberystwyth at 9 years if someone is home all day or half the day. It estimates 10 years if you are out all day. However, that is the only Welsh point in its estimate, so treat it as a guide for mid Wales only.

Ofgem sets typical household electricity use from July 2026 at 1,600, 2,500 and 3,800 kWh a year on a standard meter. A 4 kWp system can therefore make more power in a year than a medium-use home needs. However, panels make most of it in the middle of the day, so the timing of your use still matters. That is where a battery can help, as our page on solar battery storage explains.

What to ask for in a quote

Ask for the array size in kWp, the site irradiation or regional factor, orientation and inclination. Ask for the shading and loss assumptions behind the annual kWh figure. MCS warns that actual performance can differ if the installer assessed your roof remotely, so ask how they checked yours.

Compare quotes on the same basis, because different assumptions give different numbers. Our solar panel guide for Wales covers the rest of the project. When you are ready, use our get quotes page to ask MCS-certified installers for a quote. Our page on solar panel installation lists what a good quote contains.