Solar panels and underfloor heating can work well together — but the combination works best when a heat pump is in the middle. Here is why, and what the right setup looks like for an Irish home.
The Timing Challenge
Solar panels generate most electricity in summer, during the middle of the day. Underfloor heating is needed most in winter, in the morning and evening. On the face of it, this looks like a poor match — and it is, if you think of solar panels directly powering underfloor heating as their primary purpose.
But that is not quite how it works in practice, and a well-designed system can make solar and underfloor heating a genuinely effective combination.
How Solar PV and Underfloor Heating Work Together
The most effective connection between solar panels and underfloor heating in Ireland runs through a heat pump. Here is why that matters:
A heat pump does not convert electricity to heat at a 1:1 ratio. It uses electricity to move heat from outdoor air into your home, with a typical efficiency (Coefficient of Performance, or COP) of 3:1 to 4:1 — meaning every 1 kWh of electricity produces 3–4 kWh of heating energy. So solar electricity used to run a heat pump is effectively multiplied three to four times before it reaches your underfloor heating.
The Recommended Setup for Irish Homes
Solar PV Panels
Generate electricity from daylight. Size the system based on your total electricity consumption including heat pump usage — typically 5–8 kWp for a home relying heavily on a heat pump for heating.
Air-to-Water Heat Pump
Uses solar electricity (and grid electricity when solar is insufficient) to heat water for your underfloor heating circuits. Heat pumps run efficiently at the low water temperatures underfloor heating requires — typically 35–45°C, versus 70°C+ for radiators.
Wet Underfloor Heating System
Warm water circulates through pipes in your floor. The floor slab acts as a thermal store — it takes time to heat up but also retains heat for hours. This thermal mass means you can heat the floor during peak solar hours and benefit from that heat well into the evening.
Battery Storage (Optional)
Adds flexibility — stores solar surplus for use in the evening or overnight. With a heat pump and underfloor heating, a battery can extend your solar self-consumption significantly. Whether it is worth the additional cost depends on your overall system size and usage.
Electric Underfloor Heating vs Wet Underfloor Heating
There are two main types of underfloor heating in Irish homes:
Wet (Hydronic) UFH
- Warm water circulates through floor pipes
- Works with heat pump, boiler or solar thermal
- Most efficient with a heat pump
- Better for whole-home heating
- Higher install cost, lower running cost
- Best pairing with solar PV + heat pump
Electric (Dry) UFH
- Electric heating elements under the floor
- Converts electricity to heat at 1:1 ratio
- Simpler to install, lower upfront cost
- Better suited to individual rooms
- Can use solar electricity directly
- Higher running cost than heat pump option
If you have electric underfloor heating, you can use solar electricity to run it directly — but you lose the heat pump multiplication effect. It still reduces your running costs but not as dramatically as the heat pump route.
The Financial Case
Homes with solar PV, a heat pump and underfloor heating can achieve annual energy savings of €1,200–€2,000 or more compared to a home on gas or oil heating without solar. The exact saving depends on system sizes, home insulation, usage patterns and electricity tariff.
The key is that the combination makes each part work harder. The heat pump makes solar electricity go further. The underfloor heating's thermal mass allows you to heat when solar is generating rather than just when you need heat. The result is a genuinely high self-consumption rate and strong overall economics.
SEAI offers grants for both solar PV and heat pump installations. These are separate grants and can potentially be combined. Visit seai.ie for current grant amounts and eligibility — both programmes are subject to change.
Frequently Asked Questions
Solar panels can contribute to powering underfloor heating, but the most effective combination is solar panels paired with a heat pump running underfloor heating. The heat pump's efficiency amplifies each unit of solar electricity into significantly more heat energy, making the combination far more effective than solar electricity used directly for heating.
The most effective setup is solar PV panels combined with an air-to-water heat pump running a wet underfloor heating system. The heat pump uses solar electricity to heat the home, and the floor slab retains heat for hours. This lets you heat during peak solar hours and benefit from that heat into the evening.
Solar thermal panels can be used with underfloor heating systems but this is a less common setup in Ireland today. Most modern installations use solar PV combined with a heat pump rather than solar thermal, which has largely fallen out of favour due to higher maintenance requirements and lower overall flexibility compared to the solar PV and heat pump combination.
Home Solar Panels Ireland
Practical, honest information about solar panels for Irish homeowners. We explain how solar works in Ireland, what it costs, and whether it makes sense for your home — without the sales pitch.
