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?
Potential Savings are Higher With Solar PV
Water heating uses a lot of energy1, so solar thermal can give you big savings on your bills. However, solar PV gives you even more savings. This is because solar PV can power any electrical appliance in your home, along with heating water.
Solar PV Requires Almost No Indoor Space
Solar thermal systems require significant plumbing. In particular, you might have to get a bigger hot water tank. This makes people with solar thermal complain they “have no room in their hot press any more”.
In contrast, a solar PV power diverter can give you hot 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, PV hardware can be located out of the way in your attic or garage.
Solar PV is More Reliable
Solar thermal systems require a pump to move fluid through the system. Unfortunately, this means 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.
Solar Thermal Requires Less Roof Space
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 roof space.
Higher Grants for Solar PV
You can get grants for both solar PV and solar thermal. However, solar PV grants are significantly higher (up to €3,000) than solar thermal grants (€1,200).
Make Money Selling Surplus Solar PV Electricity
Beginning in summer 2021, you can sell your surplus solar PV electricity to the grid in Ireland. This could be a nice extra income solar PV owners. You can’t sell surplus solar thermal hot water unfortunately!
Conclusion – Solar PV vs Solar Thermal
For most people, solar PV is a better option than solar thermal. However, if you’re short of roof space, then consider a solar thermal system.
Reference
1: Energy in the residential sector (2018). Sustainable Energy Authority of Ireland.