Thermodynamic solar panels Ireland buyers come across are often marketed as “solar panels that work day and night, rain or shine”. That’s partly true, because they aren’t really solar panels in the usual sense. They’re a type of heat pump for hot water. This guide explains how they work, how they compare with solar PV and solar thermal, what independent testing found, and where they stand on SEAI grants. Checked 26 October 2026.
What are thermodynamic panels?
A thermodynamic system has a thin metal panel on a roof or wall, connected to a unit with a compressor and a hot water cylinder. A refrigerant flows through the panel at a very low temperature, so it absorbs heat from the surrounding air (and some from the sun). The refrigerant turns to gas, a compressor raises its temperature and that heat is passed to the water. TheGreenAge describes the coolant running at between -20°C and -30°C, which is why the panel can pick up heat even on cold, cloudy days.
In other words, it works like an air-source heat pump, with the panel acting as the outdoor collector instead of a fan unit. It produces hot water, not electricity, and the compressor uses electricity to run.
Thermodynamic vs solar PV vs solar thermal
| Solar PV | Solar thermal | Thermodynamic | |
|---|---|---|---|
| Produces | Electricity | Hot water | Hot water |
| Main energy source | Sunlight | Sunlight | Ambient air heat, plus a compressor |
| Uses electricity to run? | No (generates it) | A small pump | Yes, the compressor |
| Works at night? | No | No | Yes, but less efficiently in cold weather |
| SEAI home grant | Up to €1,800 + €600 battery | €1,200 | Not listed on SEAI’s grant pages |
Solar thermal panels heat water directly using the sun. SEAI says well-installed systems provide up to 60% of hot water demand over a year (SEAI). Solar PV generates electricity you can use for anything, including heating water through a diverter.
What testing found
Independent test data is limited. A discussion paper by Narec Distributed Energy (NDE), a UK test centre, monitored a single-panel, 210-litre thermodynamic unit in its lab and measured monthly average coefficients of performance (COP: units of heat out per unit of electricity in) from 1.43 in January to 2.27 in August, with daily values close to 2.5 on some days (NDE discussion paper). The paper found that COP varied more with air temperature than with daily sunshine.
Put simply, under those test conditions the system delivered roughly 1.4 to 2.3 units of hot water heat for every unit of electricity, depending on the season. That’s better than an immersion (about 1), but the authors noted a longer monitoring period would give more confidence. It is one test of one unit, so treat it as indicative.
Thermodynamic solar panels Ireland: grant status
As of 26 October 2026, we couldn’t find thermodynamic panels listed on any SEAI home grant page:
- SEAI’s solar water heating grant (€1,200) covers solar thermal systems and doesn’t mention thermodynamic panels.
- SEAI’s heat pump grant lists air-to-water, ground-source, exhaust-air, water-to-water and air-to-air systems, and doesn’t mention hot-water-only heat pumps or thermodynamic panels.
- The solar electricity grant is for PV panels and batteries only.
If a seller tells you a thermodynamic system qualifies for an SEAI grant, ask them to show you in writing which scheme and category, and confirm with SEAI before you sign. Don’t assume it does.
Pros and cons
Potential advantages
- Produces hot water year-round, including at night and in cloudy weather
- The panel is light and can go on a wall or roof that doesn’t face south
- Can replace or reduce immersion use for hot water
Drawbacks
- Uses electricity to run the compressor, so it isn’t free to run
- Hot water only; it doesn’t generate electricity or export to the grid
- No SEAI grant listed, unlike PV and solar thermal
- Limited independent performance data
- Efficiency falls in cold weather, when you need hot water most
Questions to ask a thermodynamic seller
- What seasonal or annual COP do you expect for my home, and what is it based on? Ask for independent test data, not just brochure figures.
- How much electricity will the compressor use in a year, and what will that cost at my unit rate?
- Which SEAI grant, if any, does this system qualify for? Please show me in writing.
- What happens to hot water supply if the compressor fails, and is there an immersion back-up?
- What warranties cover the panel, compressor and cylinder, and who services the refrigerant circuit?
- Is the installer qualified to work on refrigerant systems, and will the electrical work come with a completion certificate?
Compare the answers with a quote for solar PV with a diverter, or solar thermal, for the same hot water demand. Only then can you judge value.
Is there a better option for your home?
It depends on what you’re trying to achieve. If your main goal is cheaper hot water and lower bills overall, a common alternative is solar PV with a hot-water diverter, which uses surplus solar electricity to heat the cylinder and qualifies for the SEAI PV grant and 0% VAT on supply and installation (Revenue). If you’re planning a heat pump for space heating anyway, it will usually provide hot water too, with an SEAI grant. Solar thermal remains grant-aided at €1,200.
For an overview of grant-aided options, see our solar grants guide and our solar panels for homes page. If you’re weighing panels against other options, our best solar panels guide explains what to look for in PV modules.
FAQs
Do thermodynamic panels work in Ireland’s climate?
They work in cold and cloudy weather because they draw heat from the air, but efficiency drops as temperatures fall. In NDE’s test, monthly COP ranged from 1.43 in January to 2.27 in August.
Are thermodynamic panels the same as solar panels?
No. Solar PV makes electricity from sunlight. Thermodynamic panels are part of a heat pump system that makes hot water, using a compressor powered by electricity.
Can I get an SEAI grant for thermodynamic panels?
We couldn’t find them listed on SEAI’s solar water heating, heat pump or solar electricity grant pages as of 26 October 2026. Confirm directly with SEAI before buying.
Is solar PV with a diverter better than thermodynamic panels?
For many homes it’s the more flexible choice, because PV electricity can power the whole house and export surplus, and it’s grant-aided. A diverter then sends spare electricity to your hot water. Ask installers to compare both for your usage.
Do thermodynamic panels need planning permission?
Treat them as you would any roof- or wall-mounted collector and check with your council, especially for wall mounting or if your home is a protected structure.
Get your solar quote today
Get your solar quote today. Not sure which technology suits your home? Tell us what you want to achieve and we’ll connect you with SEAI-registered solar installers for itemised quotes. Call 089 450 4544 if you’d rather talk it through.
