"Peter Parry" wrote in message
...
On Wed, 23 Nov 2005 15:05:37 +0000, David Hansen
wrote:

On Wed, 23 Nov 2005 12:41:15 +0000 someone who may be Peter Parry
wrote this:-

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

Incorrect.

Solartwin make quite a lot of one of the reports you mentioned.

Indeed they do - most misleadingly. As with all other manufacturers
they also, as I stated, avoid real figures like the plague and have
no link to download the report they quote. Instead there is a
rambling missive about vague greenery and a wholly ridiculous claim
that the value of your house will go up by at least GBP1,000 and your
boiler get two years of extra life.

http://www.solartwin.com/questions_a...s.htm#evidence

"Where's the evidence of this 20%?

20% of what? They present it as if it is a huge saving, in fact the
performance of their product is pretty middle of the road in a bunch
which collectively are dire.

"In this study, flat plate solar hot water systems negated an
average of 17% of their potential global warming benefits (i.e. CO2
savings) by using mains electricity.

Which fails to mention that the benefits are minimal to begin with -
17% of 2/3 square root of sod all is still sod all.

"For partial-vacuum tubes ("solar tubes"), their loss averaged even
higher, at 23%.

The loss was exactly the same - this is simple dishonest use of
percentages to make a marketing point.

Solar water heating is much like double glazing. If you do it just
to save money then you are not going to do very well out of it.
However, if you do it for a whole range of other reasons then the
investment makes perfect sense.

It is nothing like double glazing. Double glazing brings with it a
number of other advantages such as better noise insulation, less
condensation and improved comfort within rooms by eliminating
draughts. Solar water heating has no advantages at all over any
other form of water heating, however, as well as making no economic
sense is visually unattractive and also a very unreliable heating
source.

Solar water heating will never make sense in the vast majority of
situations in the UK.

It will if it is designed and built into new homes, renovations and
extensions. If it is made mandatory the capital cost will plummet and it
will be viable.