Solar PV Vs Solar Thermal

The basic difference between solar PV (photovoltaic) and solar thermal is that PV produces electricity while thermal produces hot water. But which is the better option for Irish households?

Solar thermal panel with hot water tank on a roof; Array of solar PV panels on a roof.
Solar thermal (left) versus solar PV (right). Notice the water tank at the top of the solar thermal panel and the pipe fitting at the bottom. Credits: ResoluteSupportMedia licensed under CC BY 2.0 (solar thermal); trochej licensed under CC BY 2.0.

Potential Savings

Water heating uses a lot of energy1, so you can make worthwhile savings by installing solar thermal. However, solar PV can provide even greater savings because PV can power any electrical appliance in your home, along with heating water.

Indoor Space Requirements

Installing a solar thermal system requires significant plumbing. In particular, you might have to get a much bigger hot water tank. This makes many people with solar thermal complain that they “have no room in their hot press any more”. In contrast, a solar PV power diverter can give you hot water water with no change to your plumbing. Overall disruption is minimal with solar PV because it takes up only a tiny amount of indoor space. Better still, any PV hardware can be located out of the way in your attic or garage.


Solar thermal systems require a pump to move fluid through the system. Unfortunately, this means that pump failures and pipe leaks can be a problem. You will have to maintain these parts periodically. On the other hand, solar PV systems have no risk of leaks and require little or no maintenance.

Roof Space Requirements

Solar PV systems start with as little as 3 square meters, but 10-30 square meters is more common. In contrast, solar thermal systems generally need much less roof space. 2-7 square metres is usual for solar thermal. Because of this, solar thermal can be the winner if don’t have much space.


For most people, solar PV is a better option than solar thermal. However, if you don’t have enough roof space for solar PV then consider solar thermal. I hope this post has made the difference between solar PV and solar thermal clearer. If you have any questions make sure to ask in the comments below!


1: Energy in the residential sector (2018). Sustainable Energy Authority of Ireland.

2 thoughts on “Solar PV Vs Solar Thermal”

  1. Seamus Conlon

    Hi Dominic,

    Like the website, lots of info. I had to look up PV as I did not know that it stood for photovoltaic. I think you should mention this in the intro on the home page. For such abbreviations It’s usual to write the term out in full first with the acronym in brackets after, eg photovoltaic(PV) and then you can continue to use PV thereafter. Just my opinion!


Leave a Comment

Your email address will not be published. Required fields are marked *