Heat Pumps and Solar Panels in Ireland

What if you want to install both a heat pump and solar panels? This guide explains if you can (and should) do so.

TL;DR:

If you already have a heat pump, solar PV is a great addition. But solar thermal would probably not be worthwhile.

Already having solar PV prepares you very well for installing a heat pump. And having solar thermal panels need not be an obstacle to getting a heat pump.

Background on Solar Panels and Heat Pumps

First, a little background info to set the scene.

There are two kinds of solar panels in Ireland. The first kind is solar PV (photovoltaic). Solar PV panels generate electricity. The second kind is solar thermal. Solar thermal panels heat water for taps and showers.

Image showing two neighbouring in Ireland.  The house on the left has solar PV panels, while the house on the right has solar thermal panels.  Notably, the PV solar panels occupy much more space than the solar thermal panels.
Solar PV panels (left) and solar thermal panels (right) are totally different technologies

Meanwhile, the main job of a heat pump is usually space heating. But many heat pumps can also provide hot water for taps and showers. This is true both for ground-source (geothermal) heat pumps and air-source heat pumps.

Can Heat Pumps and Solar PV Panels Work Together?

Yes, heat pumps and solar PV panels work great together. PV solar panels generate electricity, while heat pumps consume electricity. Moreover, there is generally no conflict between the two technologies, because they’re installed in totally different locations. Specifically, solar panels generally go on a roof, while a heat pump will be placed outside (monobloc) or in an outhouse/utility room (split system).

PV solar panels on the roof of a house in Ireland
PV solar panels are compatible with heat pumps

Is it Worth Having Both A Heat Pump And Solar PV Panels?

Heat pumps and PV solar panels compliment each other very well. Indeed, there’s no cheaper way to power a heat pump than with your very own electricity harvested on your roof. So solar PV panels and heat pumps are a great pair – just like Jack Sprat and his wife! So it certainly can be worthwhile having both.

On the other hand, it’s unrealistic to expect 100% of the electricity for your heat pump to come from solar panels. This is because heat pumps are generally designed to run continuously – and solar panels can’t power them through the night. So there’s one more ingredient to add to this mix – a day/night or smart electricity meter. This will let you compliment daytime solar energy with night-rate electricity to power your heat pump at the lowest overall cost.

Besides, with solar feed-in tariffs now live in Ireland, you can offset the cost of electricity you consume with electricity you sell to the grid. So, with a heat pump and plenty of solar panels, your energy bills can be ultra-low. Think about it: No oil bill, no gas bill – only one small electricity bill every two months.

No oil. No gas. Just a small electricity bill. What can be achieved with the ultimate combination of insulation, a heat pump, and plenty of PV solar panels.

One important side note: A heat pump is not suitable for every home – solar or no solar. In particular, your home needs to be well-enough insulated for a heat pump to work efficiently. If you have doubts then read: Is a Heat Pump Worth it in Ireland?

What About Solar Panel Power Diverters and Heat Pumps?

A solar panel power diverter is a device that heats water using surplus electricity from PV solar panels. It does this by sending the surplus electricity to your immersion heater. Many heat pump units also use an immersion heater for back-up and to Pasteurise Legionella bacteria in hot water tanks. Unfortunately, you generally can’t connect a power diverter and a heat pump to the same immersion element.

There are several possible solutions to this dilemma:

  • Use a hot water tank with multiple immersion heaters. Connect the heat pump to the bottom immersion heater and the power diverter to the top immersion heater
  • Get a custom-made immersion heater with two electrically separate elements. Or in other words, two side-by-side immersion heaters that fit into the same hole in a hot water tank. Connect the heat pump to one and the power diverter to the other.
  • Just don’t use a power diverter. With export payments for surplus solar electricity now live in Ireland, this is currently the most economically attractive option for most people with solar PV and a heat pump.
Schematic showing a hot water tank with two immersion heating elements.  The top element is connected to a solar panel power diverter.  Meanwhile, the bottom element is connected to a heat pump immersion control unit.
Solar panel power diverters and heat pumps can work side-by-side if connected to different immersion elements

Can Heat Pumps and Solar Thermal Panels Work Together

Solar thermal panels (plates or tubes) heat water using solar energy. Meanwhile, a heat pump heats water using electricity and warmth from the ambient environment. So there’s some overlap in what these two technologies do.

There are two main scenarios to consider when both solar thermal panels and a heat pump are installed in the same house.

First is the case where the heat pump provides space heating only (not hot water for taps and showers). This case is very simple – there will be no interaction between the heat pump and the solar thermal systems. And therefore, the solar thermal panels and the heat pump can work fine side by side.

Second is the case where the heat pump provides both space heating and hot water for taps and showers. In this case, it’s likely that the heat pump and solar panels will be supplying heat to the same hot water cylinder. In this case, you’ll need a cylinder with two heat exchange coils – one for the heat pump and one for the solar thermal panels. Note that both coils, but especially the heat pump coil, need to be adequately sized.

Is it Worth Having Both Solar Thermal Panels and a Heat Pump?

Households with solar thermal panels but no heat pump could have a lot to gain by adding a heat pump. This is because adding a heat pump could allow them to slash their space heating costs. They could also reduce their winter-time water heating costs.

Air-source heat pump outside a house
A heat pump mainly provides space heating. Meanwhile, solar panels generate electricity or hot water for taps and showers

On the other hand, households that already have a heat pump (one that also supplies hot water) have less to gain by adding solar thermal panels. This is because the heat pump will already provide low-cost hot water for taps and showers. So solar thermal panels would be largely redundant. On the other hand, solar thermal panels could extend the life of a heat pump by eliminating the need for it to run during the summer months. And they will provide some additional energy savings. But probably not enough to justify the cost of the panels. And in the case where the heat pump only provides space heating, solar thermal will perform just like they would in a house without a heat pump.

In practice, if you already have a heat pump, there’s usually not much point in adding solar thermal panels. Consider solar PV instead. But it could still be well worthwhile to add a heat pump to a house that already has solar thermal. As with solar PV, you also need to make sure that a heat pump is right for your home in general (leaving solar aside).

SEAI Grants for Heat Pumps and Solar Panels

You can get a grant for both a heat pump and solar panels on the same house. Claiming one grant does not make you ineligible for the other.

Specifically, the SEAI provides grants up to €6,500 for heat pumps in Ireland. Meanwhile, you can gain up to €1,200 in grants by installing solar thermal panels on your roof. Or €2,400 for solar PV.

Alternatively, the SEAI’s One-Stop Shop grants of up to €25,000 can be used towards the cost of both solar panels and a heat pump.

Ready for A Warmer Home?

A Home Energy Assessment or Technical Assessment is the first step towards your home energy upgrades. Here’s why:

  • Independent advice from an SEAI-registered and qualified professional
  • Qualifies you to apply for SEAI grants, including the €6,500 heat pump installation grant
  • Grants up to €350 towards the assessment cost

The founder of Ecoplus Survyeors Limited, Dominic has worked with sustainable energy since 2019. He writes about energy-related topics, including heat pumps and solar PV. In his spare time, Dominic enjoys playing traditional Irish music and riding mountain bikes.