That's an excellent question Neil. I have personally don't know, so will be looking to find out from others what the answer is.

I was watching a YouTube video on that very subject the other day (sorry can find the link) but it more or less said just cover your house with PV as its more productive for you and can be used for more than just heating water especially with something like an Iboost etc I think more research will be needed to understand it but in my head it seems logical that you would go with he PV as it gives you more options especially if you have limited roof space for the panels 

Hi Everyone,

Like Bob, I was doing some research for a future proposal.

Solar PV are approximately 20% efficient at the moment. New panels are being developed that could be almost 40% efficient.

Solar Thermal is up to 90% efficient and can provide plenty of hot water from one or two panels. I believe it is also much cheaper to install than Solar PV. The drawback is that you do not get any free electric.

Maybe i could use the 3 panels wide space that i have left on roof to install thermal, and that heats the hw cylinder, and then boost it at night to ensure its still warm for the morning shower 

good point - Thanks Guys.. I too have some space left on my south facing roof - perhaps will check possibilities to 3-4 panels. Now the questions is - should it be vacuum tubes or conventional black panels? which is better?

Hi Guys,

You may find the following link of use:-

https://www.viridiansolar.co.uk/resources-3-2-efficiency-of-solar-thermal-panels.html

@neilsondhi Tubes every time.. the larger the diameter the better..They are efficient at any angle over the 180 degrees of the roof as they concentrate the solar rays through an evacuated  space onto  a copper rod which will burn your hands on a heavily clouded day, so handle carefully.The tubes are fairly tough apart trom the seal at the end which is where the air is drawn out and sealed with a molten glass point. Bang this point and you may loose the vaccuum. Replacements are only about £30. Have a look at Navitron.org.uk.

@chris-in-kemnay Thanks a lot - makes sense. I have requested quote for Tube based system - hope I will be able to afford it 🙂

@neilsondhi If you have any DIY skills you can do most if not all of it yourself. I had a roofer to help me with the initial 20 tube 48mm panel on the roof, showing me how to drill the tiles with a diamond core drill and lift and replace the tiles. I did all the rest myself and although there was a bit of trial and eror its all good learning.

I would imagine a 20 tube setup would cost under £2500 including tank. But the DIY method negates the RHI unless its part and part and you get a nice installer to certify it for you.

Chris

@chris-in-kemnay - wish I could, since it involves plumbing we require certified plumber here in Hungary (at least this is what I was warned - Heating water that we consume if not done right can leak etc) will ask around if my DIY will not get me into trouble. 

The Solar water is completely separate to the water you consume.

The solar water has an antifreeze agent in it and heats your consumable water by being pumped through a coiled tube in your hot water cylinder.

The tube keeps solar and consumable separate.