On Tue, 22 Nov 2005 20:59:43 +0000 (UTC), "Graham Harrison"
wrote:

Has anyone here had domestic solar water heating installed?

My parents house had it (self install - DIY cost about GBP500 in
total using some very expensive glass vacuum collectors found in a
scrap yard - it was finding the collectors which caused the thing to
be built!) and a neighbour later had a commercial one fitted. Over
20 years neither broke even or got remotely near doing so. Both
houses had virtually ideal south facing roofs of appropriate pitch.

Two reports worth looking at are

http://www.broadband.gov.uk/energy/r.../sp300275r.pdf

and

http://www.dti.gov.uk/renewables/pub...load=01%2F1292

These do at least put some figures on the likely effects of these
units (something the manufacturers studiously avoid doing).

From those tests the amount of energy from the panels tested came to
roughly in the range 3,400 to 4,800 MJ per year. 1kw/hr (1 unit of
electricity) = 3.6 MJ so that is between 945 and 1,330 kw/hr per year
in ideal locations. If they are not south facing and at the right
angle that figure can reduce by 50%.

Assuming 1,100 kw/hr is contributed per year the equivalent fuel
costs are roughly:-

Gas (2p per kW/hr) = GBP22
Electricity (9p peak rate) = GBP99
Electricity (3p off peak rate) = GBP33

(These figures do not include any standing charge)

The saving achieved by using solar water heating in ideal situations
is therefore in the order of only GBP22 to GBP100 per annum.

As the installed cost of commercially fitted solar panels is in the
region of GBP3,000 to GBP5,000 or more it is not surprise that the
manufacturers so carefully avoid any mention of how much energy the
things actually (don't) produce and the fact they can never pay for
themselves as the payback period is considerably greater than the
system life.



--
Peter Parry.
http://www.wpp.ltd.uk/