What solar hot water is, and how it differs from solar panels
Solar hot water collectors heat water directly. They are plumbed into the cylinder, not wired into the fuse board, and they cover about half a year's hot water.
What goes in
Two or three collectors on the roof, a pump, and a coil in the hot water cylinder. Fluid runs up to the collectors, warms, comes back down and gives its heat to the water in the cylinder. On a good day the boiler never comes on and the immersion is never touched.
There are two kinds. Flat plate collectors are a sealed box with an absorber inside; they are the cheaper option and can sit in the roof or on it. Evacuated tubes are rows of glass tubes on a frame, they only go on the roof, they cost more, and per square metre they deliver about a fifth more hot water. SEAI also say the tubes hold up better in low light, which matters more here than it would further south.
There is no SEAI median cost for this work, so this site does not publish a price for it. Get two or three quotes.
Compared with the ways you heat water now
| Immersion heater | Gas or oil boiler | Solar hot water | |
|---|---|---|---|
| What it runs on | electricity at full price | the same fuel as your heating | daylight |
| In June | expensive, and it heats nothing else | fires the whole boiler for one tank | most of the tank, free |
| In December | works, at a price | works | little, and you're back on the boiler |
| Across a year | all of your hot water | all of your hot water | 50 to 60% of it, SEAI say |
| What breaks | the element | the boiler | the pump, before the collectors |
| Grant | none | none | €1,200 |
Grant €1,200 regardless of property type; home must have an MPRN and have been built and occupied before 2021. SEAI: systems are "designed to meet 50-60% of your annual hot water needs"; evacuated tubes give ≈20% more hot water per m² of aperture than flat plate. Read on seai.ie 8 September 2026. Amounts verified 2026-09-07.
Is it right for a house like yours?
Your cert may say B2 — that's a B on the new scale.
A heat pump runs on electricity. Pick "Heat pump" if you have one.
A 1990s detached house on oil, rated CEnergy rating C
- Grants you’d get
- €12,500
- It costs about
- €16,500
- You pay
- €4,000 – €4,500
- Saves you each year
- about €820
- Pays for itself in
- about 7 years
The commonest home on file — 47,829 like it. Change an answer above for yours.
Modelled, not observed payments. Middle case €4,519; a quarter of these homes are over €8,930. Repaid in 7–13.4 years. Confidence 0.9.
Show what’s included
This is the job list that suits most homes like yours (4 in 10). The money above is the middle of every route we priced, so it will not add up to this list exactly.
Is the house warm enough to hold the heat? — SEAI's test before they'll fund a heat pump. The insulation steps are usually what gets you through.
Heat Loss Indicator ≤ 2.3 W/K·m² after fabric works. 29% of homes like yours already pass. Assessment about €276, grant €350 through a One-Stop-Shop.
Costs about €280 · grant €350 · the grant covers it
Heat pump — replaces the boiler, runs on electricity, pulls heat from the outside air. An outdoor unit the size of a large suitcase, bigger radiators in some rooms, three to five days. Runs cooler for longer — the house feels even, not blasted.
Air-to-water, SPF 3.5 heating / 2.5 hot water. Cost €16,832 · grant €6,500 + €4,000 (replacing oil/gas/coal) + €2,000 pipework + €700 controls = up to €13,200 · you pay from €3,632. 9.8c per kWh of heat vs gas 14.4c / oil 18.0c.
Costs about €16,500 · grant €6,500 · you pay €10,000
The paperwork — assessment first, grant approval, then the work, then a new energy cert, then the grant is paid. A One-Stop-Shop does all of it and takes the grant off the bill.
Order is mandatory — work started before approval is not eligible. Energy cert €276, assessment grant €350 through a One-Stop-Shop. Typically 3–6 months end to end (estimate).
Costs about €280 · grant €350 · the grant covers it
Where the saving comes from
Hot water is a fixed cost in a way heating isn't. A well-insulated house needs less heat every year, but it needs the same number of showers. So the cylinder is one of the few places where the saving doesn't shrink as the rest of the house improves.
The catch is the shape of the year. The sun is generous in the months a house needs least and mean in the months it needs most, and no collector fixes that. That is why the honest figure is an annual one — about half — and why the boiler or the immersion stays in the house as backup.
No published cell on this site has solar hot water in its cheapest grant-eligible route to a B, so there is no modelled cost, saving or repayment time for it here — the model reaches the target more cheaply by other means. SEAI publish no median cost for solar thermal either; the €9,400 median shown for solar panels on a semi is for photovoltaics, a different technology.
Common questions
- How much of my hot water will it cover?
- SEAI put it at 50 to 60% of a year's hot water on the grant page, and up to 60% over twelve months on their technology page. Both of those are annual figures and they hide a big swing — close to all of it on a bright week in June, close to none of it in December, when you are back on the boiler or the immersion.
- Flat plate or evacuated tubes?
- Flat plate collectors are cheaper and can be set into the roof as well as onto it. Evacuated tubes cost more, only go on top of the roof, and give about 20% more hot water for each square metre — and SEAI say they do better in low light, which is worth something in an Irish winter.
- Should I get this or solar panels?
- They do different jobs, so it depends on what your house needs. Solar hot water only makes hot water, and it makes a lot of it in summer, when a house needs least. Solar panels make electricity you can use for anything, including sending the extra to the immersion. Most houses being upgraded today are being fitted with panels; the grant for hot water is there for the ones where hot water is the problem.
Where to next
Where this comes from
Last checked 2026-09-08.