How Many Solar Panels Do I Need?
Enter your electricity usage and roof details to get a recommended system size, panel count and savings estimate.
Co. Waterford: 1,150 kWh/kWp/yr (south, optimal tilt)
Average Irish home: 4,200 kWh. Check your electricity bill.
Standard panel: 1.7m × 1.1m. Count how many fit on your available roof space.
Current Irish average: €0.195/kWh. Check your supplier.
Irish regulation: Domestic single-phase PV is limited to 5.99kVA (~6kW). ESB Networks enforces a 25A per phase AC output limit. Max ~14 × 400W panels. For larger systems check with your installer and ESB Networks.
Yield: 943 kWh/kWp/yr (1150 × 100% × 100% × 82%)
A
9-panel system
will cover approximately
81%
of your annual electricity usage
3.6kW · 3,395 kWh/yr · saves €1,010/yr
Seasonal coverage (9 panels)
Summer
May – Aug
147%
Winter
Nov – Feb
24%
Annual
average
81%
Your system generates more than you use in summer — the surplus is exported and earns FIT income. A battery would store more of this for evening use.
Battery comparison (9 panels)
Without battery
Bill offset: 40%
Exported: 1,697 kWh
€1010/yr
With 9kWh battery
Bill offset: 57%
Exported: 1,018 kWh
€1150/yr
Battery adds +16% bill coverage and €140 extra savings/yr
9kWh battery: €8,100 − SEAI €600 = €7,500 net
Build your own system
Coverage
81%
Generation
3,395
kWh/yr
Savings
€1010
/yr
Payback
4
years
Monthly generation (3.6kW system)
Irish climate: Ireland's cloud cover means October to March generates about 25% of your annual solar. A battery stores summer surplus for winter evenings.
FIT income: With FIT you get paid for every kWh you export. In Ireland more panels = more export income. Install as many as your roof and inverter allow.
Ireland's maximum domestic solar system is 5.99kW — approximately 14 × 400W panels.
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Last verified: 2026-06-01