Ask three installers how many solar panels you need and you will get three different answers, because the honest answer is it depends on four numbers, and none of them is the number of bedrooms. Most Irish homes land between 3 and 6 kWp, roughly 8 to 14 panels, and this guide shows you how to find your spot in that range before anyone stands on your roof.
- Typical Irish system
- 3 to 6 kWproughly 8 to 14 modern panels
- The sweet spot
- About 4 kWpwhere the SEAI grant reaches its €1,800 max
- What each kWp makes
- ~850 to 950 kWh a yeardepending on roof direction and shading
- Average home usage
- ~4,200 kWh a yearyour bill knows your real number
- Roof space per panel
- ~2 m²a typical rear roof fits 8 to 12
The four numbers that size a solar system
Your annual electricity use
Find the kWh figure on your bill. Matching generation to real usage, not house size, is the whole game.
Your usable roof
Clear, unshaded area facing south, east or west. Each panel wants about 2 square metres; chimneys, windows and valleys take bites out.
The grant structure
SEAI pays €700 per kWp for the first 2 kWp and €200 per kWp up to 4 kWp, capping at €1,800. Beyond 4 kWp, panels still pay, just without extra grant.
Your future usage
An EV, a heat pump or home working push usage up. Sizing for next year’s life, not last year’s, is what stops systems being outgrown.
What solar could mean for your bill
Electricity is a bill you pay for life, which is why panel maths gets interesting over decades, not months. Drag your annual electricity spend and look at the 25-year picture, the working lifetime of a quality system:
The exact share solar covers depends on sizing and how much you use during daylight, which is why the grant guide walks through self-consumption and export payments in detail.
Is your home a good fit?
Bigger is not always better
A solar quote should never just be “as many panels as fit”. Oversizing wastes money on generation you export cheaply; undersizing leaves free roof and grant unused. The right system covers a strong share of your daytime usage, uses the full grant band where the economics are best, and leaves room for the future. And remember the wider order of works: a warm, insulated home needs less energy in the first place, which makes every panel you buy work harder.
Questions people ask
Do east or west roofs really work?
Yes. A south roof peaks hardest at midday, but east and west spread generation across morning and evening, which often matches when families actually use electricity. Plenty of Irish systems split panels across two aspects deliberately.
Should I wait for better panels?
Panel efficiency creeps up each year, but waiting costs you every year of bills in the meantime, and the grant is here now. The maths almost always favours installing when your roof and usage are ready.
What about a battery?
A battery raises how much of your own generation you use, and suits homes that use most electricity after dark. It is an addition to sizing, not a replacement for getting the panel count right first.
Do I need planning permission?
Rooftop solar on houses is generally exempt from planning permission in Ireland, with limited exceptions such as some protected structures. For the vast majority of homes it is a straightforward install.
The bottom line
The right number of panels is the one that matches your usage, your roof and the grant band: for most Irish homes that is 3 to 6 kWp, with about 4 kWp, 9 or 10 panels, the most common answer. Size it from your bill, not your bedroom count, and the system pays from day one, with up to €1,800 of SEAI support making the start cheaper.
If you are in Cork or anywhere in Munster, book a free assessment. Bring one electricity bill, and we will bring the panel count, the grant figure and the payback maths.
