How many solar panels do I need in Ireland? It depends on three things: how much electricity you use, how much usable roof you have, and what the SEAI grant will pay for. For an average home using about 4,200kWh a year (the CRU figure quoted by Bonkers.ie), a system of roughly 4–5kWp, about 9–11 panels, would produce about as much electricity in a year as the house uses. But matching annual use isn’t always the best target. This guide shows you how to work out a sensible number.
Step 1: find your annual electricity use
Add up the kWh on your last 12 months of bills, or download your usage from the ESB Networks customer portal if you have a smart meter. A full year matters because winter and summer use are very different. Then think ahead: an electric car or heat pump will add considerably to your use, so mention these to installers.
Step 2: estimate output per kWp
Using the EU’s PVGIS data, PureVolt estimates a south-facing panel at 30° produces about 913kWh per kWp per year on average in Ireland, from about 782kWh in Donegal to about 986kWh in Cork. East- or west-facing roofs produce less per panel, but spread output across the morning and evening, which can suit Irish households.
Step 3: convert kWp into panels
Most panels now sold in Ireland are about 430–485W each and about 2m² in area (see our best solar panels guide). At 450W, 1kWp is just over two panels. The table divides annual use by 913kWh/kWp to find the system that would produce about the same amount over a year.
| Annual use | kWp to match annual use | Panels at 450W | Approx. roof area |
|---|---|---|---|
| 2,500kWh | about 2.7kWp | about 6 | about 12m² |
| 4,200kWh (average home) | about 4.6kWp | about 10 | about 20m² |
| 6,000kWh | about 6.6kWp | about 15 | about 29m² |
| 8,000kWh (e.g. with EV or heat pump) | about 8.8kWp | about 20 | about 39m² |
How many solar panels do I need in Ireland to get the full grant?
The SEAI Solar Electricity Grant (checked 26 October 2026) pays €700 per kWp up to 2kWp, then €200 per extra kWp up to 4kWp, with or without a battery, plus a €600 battery grant. That makes up to €1,800 for panels and €2,400 with a battery; confirm the exact amount on your letter of offer. Nothing extra is paid above 4kWp. That gives three natural sizes:
- About 2kWp (4–5 panels): gets €1,400, the highest grant rate per kWp. SEAI says about 80% of a 2kW system’s output is used at home in an average house.
- About 4kWp (9–10 panels): gets the maximum €1,800 panel grant, or €2,400 with a battery.
- 5–6kWp and above: no extra grant, but often cheaper per kWp because scaffolding and labour are shared. One installer told the Irish Times that labour costs are “nearly the same” whether you fit six or ten panels.
Should you match your annual use?
Not necessarily. Solar produces most in summer and very little in December, while many homes use most in winter. A system sized to your full annual use will export a lot in summer, and exports are paid at a lower rate than you pay to buy power. So:
- If you’re out during the day and don’t want a battery, a smaller system (2–3kWp) uses more of what it makes.
- If someone’s home during the day, or you have a battery, EV or diverter, a bigger system makes more sense.
- Export still earns money: the Irish Times cited a Clean Export Guarantee rate of about 19.5c/kWh in October 2026, and export income is tax-free up to €400 a year (Revenue).
Grid limits on system size
Most Irish homes are single-phase. ESB Networks’ micro-generation process (form NC6) covers inverters up to 25A, about 6kVA, on single-phase, or 16A per phase, about 11kVA, on three-phase (ESB Networks). Larger systems go through the mini-generation process, which needs an application and a fee (ESB Networks). Your installer handles this.
Roof checks that change the number
- Shading from chimneys, trees or neighbouring buildings
- Dormers, roof windows and vents that break up the space
- Edge clearances required by the planning exemptions
- Roof condition: replace an ageing roof first
- East/west splits: you may fit more panels across both slopes
For more on layouts and inverters, see our solar panels and system options guide.
A worked sizing example
Here’s how the steps fit together for a hypothetical household. The figures are illustrative, not from a real customer.
- Annual use from bills: 4,200kWh, plus an EV planned next year that the owners expect to add about 2,000kWh
- Roof: south-west facing, about 25m² of unshaded space after clearances
- Matching today’s use: 4,200 ÷ 913 ≈ 4.6kWp, about 10 panels at 450W (about 20m²)
- Allowing for the EV: 6,200 ÷ 913 ≈ 6.8kWp, about 15 panels, which needs about 30m² and wouldn’t fit
- Sensible answer: fill the usable roof with about 12 panels (about 5.4kWp), with a hybrid inverter so a battery can be added later
SEAI’s grant would be €1,800 for the panels, or €2,400 with a battery. A south-west roof will produce a little less than the south-facing average, so ask the installer for an estimate for your exact orientation and pitch.
What size battery goes with your panels?
Batteries are measured in kWh of storage. To qualify for SEAI’s battery grant, Solarinfo.ie reports the battery must be 5kWh or larger; check SEAI’s technical requirements. Batteries are getting bigger: one installer told the Irish Times the average battery it fits had risen from 6kWh to 9.6kWh in 18 months. A useful rule is to size the battery to the surplus you’d otherwise export on a typical day and your evening use, not to the panels alone. Our battery storage advice explains more.
FAQs
How many solar panels does an average Irish house need?
Producing the equivalent of 4,200kWh a year takes about 4.6kWp, roughly 10 panels at 450W. Many homes choose 2–4kWp to match SEAI’s grant bands.
How many panels is 4kWp?
About nine panels at 450W, or ten at 400–430W.
Can I have too many solar panels?
You can exceed what’s worth it. Above 4kWp there’s no extra grant, and surplus is exported at a lower rate. On single-phase, the inverter is normally limited to about 6kVA under NC6.
How much roof space do I need?
About 2m² per panel, plus clearances. A 4kWp system needs roughly 18–20m² of usable roof.
Get your solar quote today
Get your solar quote today. Send us your rough annual usage and roof details, and we’ll connect you with SEAI-registered installers who will survey and size a system to your home.
