Every figure below comes from a published source rather than a guess: the SEAI grant tiers as they stand in August 2026, county-level yield figures, current supplier export rates, and the installed cost ranges from our own solar panel cost guide. The one thing no calculator can do is price your roof. Treat the output as a shortlist-narrowing number, then get real quotes.
Calculate your solar cost and payback
| Bill saving (electricity you use yourself) | — |
| Export income (surplus sold to the grid) | — |
| Total benefit per year | — |
| Installed cost before grant | — |
What the calculator is actually doing
Four numbers drive the whole thing, and it is worth knowing which of them are fixed and which are estimates.
1. The SEAI grant is fixed, and it is pro-rata
The grant is not a flat amount and it is not rounded to whole kilowatts. SEAI pays €700 per kWp for the first 2 kWp, then €200 for every additional kWp up to 4 kWp, capped at €1,800. SEAI's own worked example on the scheme page makes the pro-rata rule explicit: a 2.5 kWp system attracts €1,500.
| System size | Grant |
|---|---|
| 2 kWp | €1,400 |
| 2.5 kWp | €1,500 |
| 3 kWp | €1,600 |
| 4 kWp and above | €1,800 (capped) |
Going above 4 kWp adds no grant. That does not make bigger systems a bad idea. It just means the extra capacity has to justify itself on generation alone. The full eligibility rules, including the pre-2021 build date and the post-works BER, are in our SEAI solar grant guide.
The cap holds at €1,800 for 2026, confirmed by Minister O'Brien. Government policy is to cut it by up to €300 a year as panel prices fall, with the scheme due to end in 2029. You get the amount in effect on the day your application is created, not the day you install, and not the day you first got a quote. Cancelling and re-applying after a cut means you get the lower figure.
2. Generation depends on where you live and which way the roof points
A kilowatt-peak of panels in Waterford produces meaningfully more than the same kilowatt-peak in Mayo: roughly 990 kWh a year against 840. That is a 15% spread across the country, and it lands directly on your payback. Orientation matters about as much. South-east or south-west loses only 5–10% against due south, while east or west costs you 15–20%. Our guide to solar panel direction in Ireland covers what to do when your only viable roof faces the wrong way.
3. Self-consumption is the number most calculators fudge
This is where optimistic calculators go wrong. Electricity you use in the house is worth your import rate. Electricity you export is worth your supplier's Clean Export Guarantee rate, which currently runs from 15.89c to 19.5c. So the same kilowatt-hour is worth roughly twice as much if you use it rather than sell it.
The 35c default is deliberately mid-range. Standard undiscounted rates are higher than most people assume. Energia's standard 24-hour unit price is 42.65c including VAT as of August 2026, while a household on a new-customer discount pays closer to 30c. Electric Ireland's current plans span roughly 29.8c to 38.7c depending on the plan and meter. Put your own rate in from a recent bill. It moves the answer more than most of the other inputs.
Without a battery, a typical Irish household uses 30–50% of what it generates. A house with someone home during the day, an EV on the driveway or a heat pump running can reach 50–70%. A house that is empty from eight to six sits at the bottom of that range. Moving the household selector from "out most weekdays" to "home during the day" changes payback by around three years on the same system. That is how much this one assumption matters.
4. Cost is a range, because quotes are a range
The calculator uses the installed cost bands from our cost guide, which is why it reports payback as a span rather than a single number. Quotes for the same system on the same roof routinely differ by €2,000 or more. That spread is larger than almost any other variable here, and unlike your county or your roof angle, it is the one you can do something about.
All prices are VAT-inclusive at 0%. Since May 2023 the zero rate of VAT applies to the supply and installation of solar panels on private dwellings, so a domestic quote should carry no VAT line on the solar work. If one does, ask why before you sign.
What the calculator cannot tell you
- Whether your roof can take the system. Rafter condition, felt, shading from a chimney or a neighbour's sycamore, and usable unshaded area all cap what is physically installable. Only a survey settles it.
- Whether your grid connection is straightforward. Your installer applies to ESB Networks before installing, and that process takes at least four weeks. Most are routine; some are not.
- Which export rate you will actually get. Suppliers set their own Clean Export Guarantee rates and change them. The default here is 18.5c because several of the larger suppliers sit there, but check the current Clean Export Guarantee rates and put your own supplier's figure in.
- What electricity will cost in year eight. Payback assumes today's import rate holds. If electricity gets dearer, payback shortens. Nobody knows which way that goes.
The calculator narrows the range. Three quotes close it. Tell us your county and roof and we will match you with SEAI-registered installers. Free, no obligation, and you keep the estimate above to sanity-check what comes back.
Get Free Quotes →Frequently Asked Questions
A 4 kWp system, the most common domestic size, costs roughly €8,000 to €11,000 installed before the grant and €6,200 to €9,200 after the €1,800 SEAI grant is deducted. A 3 kWp system lands around €4,400 to €6,900 after its €1,600 grant. Prices are VAT-inclusive at the 0% domestic rate, and the spread reflects genuine variation between installer quotes rather than uncertainty in the figures.
SEAI pays €700 per kWp for the first 2 kWp installed, then €200 for each additional kWp up to 4 kWp, with a hard cap of €1,800. It is paid pro-rata, so part-kilowatts count: SEAI's own example is a 2.5 kWp system attracting €1,500. A 4 kWp system reaches the €1,800 cap, and anything larger receives the same €1,800. The grant is paid into your bank account after the works are finished and the post-works BER is published.
For a 4 kWp system on a south-facing Dublin roof with typical household usage, payback runs roughly 7 to 10 years after the grant. The range is wide because it depends on three things that vary a lot: what you pay for the install, how much of your own generation you use rather than export, and your county's sunshine. A Waterford house with someone home during the day pays back several years faster than an empty Mayo house with the same panels.
Not on a domestic supply-and-install job. Since May 2023 the zero rate of VAT applies to the supply and installation of solar panels on private dwellings, and Revenue treats the whole system under that contract: panels, inverter, wiring and labour. The zero rate does not extend to commercial or industrial buildings, and EV chargers are treated separately. Quotes from Irish domestic installers should therefore show no VAT on the solar work.
It can be, but the extra capacity has to earn its keep without grant support. Above 4 kWp every additional kilowatt-peak costs you the full installed price, and the electricity it generates is more likely to be exported at 15.89c to 19.5c than used at around 35c, because your daytime demand has not grown just because the array did. Bigger systems make most sense where daytime consumption is genuinely higher: a heat pump, an EV charged at home, or a household that is in during the day.
A battery raises self-consumption, which raises the value of each unit you generate, but it also adds cost and attracts no grant. The battery grant ended in February 2022. Fitting 5 kWh at the same time as the array is the cheap way to do it: PureVolt publishes €1,300 to €1,400 as the marginal cost on top of the system price, and that is the figure the calculator uses. Buying storage separately is a different number entirely. Energia's 2026 guide quotes €1,500 to €7,000 across capacities, and retrofitting later costs considerably more because it usually means changing the inverter too. Whether it pays back depends on how much surplus you currently export; a house already using half its generation has less to gain than one exporting most of it.
Sources: SEAI Solar Electricity Grant for grant tiers, pro-rata rule, eligibility and payment process (accessed 11 August 2026); Citizens Information: Grants for solar panels for the grant taper and 2029 end date; Revenue: VAT on solar panels for the zero rate on supply-and-install; Energia tariff rates and Electric Ireland price plans for current residential unit rates (accessed 11 August 2026); PureVolt battery storage guide 2026 for the marginal cost of 5 kWh storage fitted with a new array; installed cost ranges and county yield figures from our own solar panel cost guide; export rates from our Clean Export Guarantee rates tracker.
Published: 11 August 2026. Author: Neil Russell.