"Andrew Gabriel" wrote in message
...
In article ,
David Hansen writes:
On 26 Jan 2008 17:02:39 GMT someone who may be
(Andrew Gabriel) wrote this:-

Hot water system which is DIY installed is the only
thing at the moment which is even remotely viable.

If one measures viability only in terms of simple payback period.

For most people, that will be the only measure. For a few
people, energy payback might be a consideration, but photo-
voltaics really struggle to produce more energy during their
lifetime than they consume in manufacture, so there's no big
win there.

For a really few geeks like me, I'll pay extra just for my
own opportunity to play with the technology. E.g. I invested
in a condensing boiler long before they were mandatory and
when they were at a price premium, because the technology
interested me and I wanted to try designing a heating system
to make good use of one (which I did).

If I had a south facing roof, I would be interested in
playing with some type of solar energy project on the same
basis. However, with my roof ridge running north-south so
it's never going to work well, and needing scaffolding in my
neighbour's garden, and the outlay (even DIY'ed) with no
prospects of any realistic savings, it really is a complete
waste of effort even at the geek level.

I installed air-con with heat-pump heating a couple of years
ago, and that looks to provide viable heat. It claims 3.5kW
for 1.2kW power consumption. It's very difficult to measure
what it produces; it does output more heat than a 2kW fan
heater but I haven't got more than 2kW to compare it with
so I don't know if it reaches 3.5kW. It is limited to quite
a narrow range of outdoor temperatures -- above about 12C
and I don't seem to need it, and below about 5C and you
can't use a heat pump air exchanger as it will ice up and
waste energy defrosting itself. For quickly heating one room
it's very good, but as an energy saving measure, it's probably
a non-starter. If prices of such units drop to the level they
are in some countries where they are more common, then they
would be viable for DIY installs.

Of course if one does this then there are many things one shouldn't
install as they have infinite simple payback periods. A new
television or kitchen are examples.

Take the cost of a kitchen (I think mine was around £4k, but
as I did it piecemeal, I never actually added it up) and
divide by, say, 15 years life, and that's around £260/year,
i.e. it's costing me less than £1/day for a kitchen. That
seems like very good value.

For some values of 'value'.