On Tue, 26 Feb 2013 03:19:54 -0800 (PST), willie eckerslike wrote:

He was not too bothered, though, because he was selling to the grid.

The export price is only 3p/unit. With an installation that old I think he'll
be getting paid 43p/unit for *everything* his panels generate wether it's
exported or not. He may well be deemed to export 50% of that total generation
as well so gets 46p/unit for half of it *and* if he uses it himself doesn't
have to buy power at say 10p/unit either, 56p/unit...

My father has solar heated oil filled panels on his roof, which heat
the water in his hot water tank. From my experience of those, when the
sun shines, even on a spring or autumn day, the water gets very hot.

Not heard of oil filled solar thermal panels, it's normally water with a lot
of antifreeze (unless you have a drain back system). 30 mins of solar
thermal activity so far today, it's not a particularly bright day either.
Delta T across the thermal store was about 20 degrees and with a 3l/min flow
rate through the collect that's something over 4kW. I have a couple of spare
1-Wire temperature sensors I think I'll attach them to the flow/return of the
solar loop will be able to see how much energy it yields then.

If I had the choice, I think I would plump for my fathers' hot water
system, but my appliances are all cold fill, so would need to be
replaced which makes it a non-starter for me.

Not sure you'd find any appliances with hot fill these days. With washing
machines the use of bio based low temperature cleaning agents means that they
have to cold fill and heat as most domestic ho****er is too hot for the bio
bits... Even if using non bio agents, heating mains water at say 15C to 40C
in on step is better than heating 15 to 60+ and cooling it. They don't use
much water either so hot fill may just fill the pipe with hot water with very
little actually entering the machine.

--
Cheers Dave.
Nr Garrigill, Cumbria. 421m ASL.