Belfast sits in the lower half of the UK range for solar output. PVGIS, the European Commission’s free solar model, estimates 919 kWh per kWp a year for a south-facing roof at 35 degrees. That is about 10% below London at 1,019 kWh per kWp, and about 3% above Aberdeen at 893 kWh per kWp.
Solar Yield is an independent estimator and does not install panels. This page explains the Belfast figures, so you can check an installer’s estimate against an open source.
What a typical Belfast system could produce
Output scales with system size. A 4 kWp system could generate about 3,676 kWh a year in Belfast, and a 4.5 kWp system about 4,136 kWh. Glasgow, at 853 kWh per kWp, sits lower.
Ofgem’s medium household uses 2,500 kWh of electricity a year on a standard meter, according to its typical consumption values. A 4 kWp roof can therefore out-produce that over a year. However, the saving depends on how much you use as the panels generate it.
Our guide to the solar panel payback period shows how to test that against your own bills.
Best month and worst month
May is the strongest month in Belfast at 122.4 kWh per kWp. December is the weakest at 26.3 kWh per kWp, so the best month produces about 4.7 times the worst.
May, June and July together give 348.6 kWh per kWp. In contrast, November, December and January together give only 94.0 kWh per kWp. Winter output is therefore small, while spring is strong.
Tilt and direction
PVGIS puts the optimal tilt for Belfast at 41 degrees, with 922 kWh per kWp a year. A 35 degree roof gives 919 kWh per kWp, so the gap is only 3 kWh per kWp. Direction matters more. Energy Saving Trust says east or west facing systems tend to produce 15% to 20% less than south facing ones.
Planning and Belfast City Council
Although Northern Ireland has its own system, the first step is the same: ask the council. According to nidirect, you may need planning permission, especially in conservation areas or on listed buildings. Power NI says roof panels on most houses are normally permitted development.
Because we could not confirm the exact size limits, we give none here. Belfast City Council is the local planning authority, so ask its planning office before you buy. Our guide on planning permission for solar panels covers the general process.
Grid connection under NIE Networks
Northern Ireland has its own network operator. In Belfast it is NIE Networks, and the equivalent of G98 is G98/NI. NIE Networks says you register systems up to 16 A per phase within 30 days of commissioning.
That differs from the 28 days in Great Britain. Larger systems follow a different route, so your installer will advise. Still, ask them which route applies to your design. Installers normally file the paperwork for you.
Cost, export and support
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. Installing solar and batteries is zero-rated for VAT until 31 March 2027. Northern Ireland has had that relief since 1 May 2023.
However, nidirect says there is no financial support for NI homeowners who generate their own electricity. The Smart Export Guarantee does not apply here, so compare supplier offers carefully.
Ask any installer to show how they reached their output figure. Under the MCS standard MIS 3002, installers multiply system size by a regional kWh per kWp value. They then apply a shade factor between 0 and 1. The estimate must reach you before you sign, and it is guidance rather than a guarantee.
Our pages on solar panel installation and solar battery storage explain how referrals work. If you also own property in Scotland, our upcoming guide to solar panels in Scotland covers the different rules there. For comparison, see the solar output figures for Glasgow and the Liverpool 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.