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Solar panels, grant, and 25 years

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Grant, self-use, and export. The SEAI formula stays editable.

Payback9 years 5 monthsJump to result
Example figures
Costs are a starting point. Confirm the grant on seai.ie.

The system

System size, kWpkWp means kilowatt-peak. It is the panels’ rated size in full sun, not the power they make on a cloudy afternoon.More detail. Nameplate DC capacity. The yearly yield box turns that rating into kilowatt-hours for this estimate.
kWp means kilowatt-peak: the panels’ rating in full sun.
Panels and fitting, before the grant. Add the battery below if you are buying one.
SEAI formula for this size: €1,800. Last checked 2026-11-03.
More options

Electricity

Generation, kWh per kWp per year
830 is the top of SEAI’s 8–9.5% capacity-factor band. A measured Dublin roof has been higher.
Used in the house, %
A planning guess. Without a battery many homes use about a third. With one, people often type 50–70%.
SEAI band DD, 33.92 cent, 1 October 2026 table. Not a live tariff.
Electric Ireland’s published microgen rate is 19.5 cent. Your supplier sets its own.
Output lost each year, %
0.5% is a common panel-warranty planning figure, not an SEAI measurement.

Payback

Simple payback
9 years 5 months
From 7 up to 12 years.
Net cost
€7,700.00
Install cost, including a battery if you added one, minus the grant
First-year saving
€814.96
3,320 kWh generated
Grant used
€1,800.00

You are paid less for electricity you send to the grid than you pay to buy it. Using a unit at home is worth more than exporting it.

Year-1 split

Used at home: 1,162 kWh. Exported: 2,158 kWh.

Later years fall by the degradation you set. The chart is 25 years and skips loans, VAT, and a new inverter.

-€7,700.00-€2,900.71€1,898.58€6,697.88€11,497.1706131925
Cumulative cash, €Year Cumulative cash
Where the solar figures come from

Checked on 3 November 2026. Standard grant: €700 per kWp up to 2 kWp, then €200 per kWp up to 4 kWp, capped at €1,800. A battery of at least 5 kWh adds €600, so the cap with a battery is €2,400. A 2.5 kWp system is €1,500. Source: SEAI solar electricity grant and the October 2026 application guide. The enhanced grant for some welfare payments is up to €8,400, or €9,000 with a battery. You have to meet the payment rules yourself.

The 830 kWh per kWp default is the top of the 8–9.5% capacity-factor band in the SEAI Solar PV Guide for Business (9.5% of 8,760 hours is about 832 kWh). A measured Dublin system has done about 885 kWh per kWp. Roofs differ.

The import price, 33.92 cent per kWh, is electricity band DD in the SEAI fuel-cost comparison dated 1 October 2026. The export default, 19.5 cent, is Electric Ireland’s published microgen rate. The CRU decision of 18 June 2024 says suppliers set their own Clean Export Guarantee rates. There is no single national export price. The €9,500 example cost is the semi-detached median in SEAI’s median-cost note for January–June 2026.

Assumptions and references

Assumptions

  • Year 1 generation is system size times kWh per kWp. Each later year multiplies that by one minus the degradation rate.
  • Self-consumption is the share you use in the house, valued at the import price. The rest is exported at the Clean Export Guarantee rate you type.
  • A battery does not change the physics by itself. If you add one, raise the self-consumption percentage to match what you expect.
  • The SEAI grant cannot exceed the cost of the works. The €600 battery grant in the formula needs a battery of at least 5 kWh.
  • Simple payback is the net cost divided by the first year’s bill saving. It ignores loans, inverter replacement, standing charges, and VAT changes.
  • This is not a roof survey, a grant offer, or a quote.

How this is calculated

  • Standard grant = €700 × kWp up to 2, plus €200 × each further kWp up to 4, capped at €1,800. Add €600 if the battery is at least 5 kWh, with a €2,400 cap.
  • Annual saving = (generation × self-use × import price) + (generation × export share × export price).
  • Net cost = install cost − grant. Simple payback = net cost ÷ year-1 saving.
  • The chart starts at minus the net cost and adds each year’s saving for 25 years.