Wondering if Solar could work for me?

grahamgoo

I have a 3 bed house with wet underfloor heating downstairs and radiators upstairs. Water is heated by a standard boiler (i.e. not a combi) and there is a water tank upstairs.

I'm wondering if it would be worth me considering solar panels for the underfloor downstairs. I understand that wet underfloor systems distribute water at a lower temperature than required for radiators, but I don't know whether solar would be sufficient even for this, particularly in winter when it is going to be most needed.

The good thing about the underfloor is that it does act as a heat store of sorts - it takes a while to build up but the warmth keeps on coming long after the boiler has been switched off, so a trickle effect could be ideal.

The other consideration is siting of panels. My house has a West facing roof but I also have a garage of a good size which has a south facing side.

Thanks for any thoughts and suggestions.

Martyn1981

Hiya Graham. Initial thoughts are that lower generation, and shorter days, mean that PV might not contribute much to the heating when you need it.

There are clever diversionary switches that can monitor any leccy export and divert that (and only that) into a hot water tank, so the PV could help a bit, and if your DHW is tank fed too, then that would be a bit extra in the summer months too.

However, at some point in the future, PV export will/might get metered (currently it's only estimated and paid for at 50% of generation). When that happens, and it could be many years away, then you'd lose the export rate of 4.64p/kWh, to save on gas, so depending on your bill type and tariffs, the gain maybe very small.

My suggestion would be to separate the two issues (heating and PV). Decide if PV is worth installing, and if the answer is yes, only then consider water heating with excess generation, as a separate decision.

Hope this makes sense, it's not that it won't help, it's just that the gains may be small, and the issue regarding export gets a little more complicated if we ever see smart meters with export monitoring.

Nothing wrong with a west facing roof, but expect about 15-20% less annual generation than a south facing roof. Garage roof also fine, in fact a combination of the two might give you a better generation curve through the day, and the west roof will help with teatime consumption during the BST months.

Have you considered solar thermal? Or was it solar thermal you meant, and I got the wrong end of the stick?

Mart.

grahamgoo

Thanks Martyn, that is really useful info. If solar thermal could work, then I'd certainly consider it, although I am unfortunately coming to the conclusion the neither will be particularly viable.

Thanks again,
Graham.