"Bioboffin" wrote in message
...
David Hansen wrote:
On 23 Sep 2006 11:29:56 +0200 someone who may be "Nigel"
wrote this:-

Does any one know of a site where you can roughly work out how mush
money you will save with solar panels. We are thinking of getting
them put we need to work how much we will save and how many years it
would take to get the money back.

If you are only considering simple payback then if you DIY it will
probably take a decade to recoup the expenditure at current gas
prices. In terms of money there are other things to do first.

However, there are other reasons to install solar water heating.

Please enlarge on this! We have double glazing; draught proofing; a full
layer of insulation in the attic. What do you suggest now, before going
for solar panels?

And what are those other reasons?

What BiBoffin said, cavity wall insulation. For instance, a gas heated semi
can get cavity wall insulation for £260: for other circumstances have a look
at the sites that abound.

Using my criterion of equivalent interest rate, cavity wall insulation has
to save
5% of £260 per annum to compete with the bank ( more if you want your
capital back in the end ). Now cavity wall insulation is guaranteed for 25
years, lets say it does what it says on the tin, you want about an extra £10
back per annum on top of the 5% to recoup your capital outlay. 5% of £260 is
£13, so adding £13 and £10 we need to save £23 per annum to break even.

The figures for a typical cavity wall that are given is about 35% of the
heat loss of a house. It could be more if the loft is well insulated and the
windows are double glazed and the leaks are sealed.

Anyway, let's also assume £400 per annum heating gas bills. I think I spend
something like that, it's unlikely to be too far off. That means perhaps
£130 of the heating bill is leaving through the walls each year. We need to
save £23 of that to break even, so unless cavity wall insulation is really
inefficient I reckon it's a no brainer that cavity wall insulation will not
only break even but may well be in profit in as little as 5 years.

OK, I plucked a lot of those figures out of thin air, but you see the method
I'm employing to make a decision.

If solar waterheating can come in well below the figures I've heard talked
about, then maybe it can be worthwhile, but I would like someone to present
a set of figures to me detailing capital outlay and return in energy savings
that exceeds 5%/annum and returns your capital in 25 years.

Noone is claiming solar water heating doesn't work, merely the economics of
it.

As I said, having looked at a few solar power websites, the only way to make
it economic seems to be to do it DIY, the OP never said he was going to do
it DIY, nor what the expected cost was. As a TV programme recently showed,
some people are being conned into solar heating systems which are expensive,
unsuitable for them ( east-west roof etc ) and can never deliver the savings
claimed.

regards,

Andy.