"YAPH" wrote in message
...
On Tue, 21 Apr 2009 00:15:15 +0100, Doctor Drivel wrote:

What figures do you have on this?

65% and 90% SEDBUK efficiencies, circa £2K for a boiler replacement and
take your choice of interest rates and gas prices averaged over the next
few years.. The rest is O-level maths.

You need to do some figures. Going from 60% to 92% saves a hell of a
lot of expensive gas.

Where do you get 60% and 92%?

But in any case you've got to compare your 'hell of a lot' with the other
hell of a lot of expensive boiler replacement.

approx £1,500 per ann. gas bill on 60% efficiency. That saves approx £500 a
year. £2K to replace a boiler to 92% efficiency and the payback is 4
years - on current gas prices. As the gas prices go up over the next 3
years the payback shortens. Sounds good to me and you have a new boiler
with maybe a 3 to 5 years guarantee. After the payback period you have a
cheaper to run boiler, a selling point if selling the house, and maybe lots
of space released.

The Zenix heat recovery top box is one of the few eco additions that really
does do what they say. Solar panels can have a payback of 10 years, while
these top boxes can take 3, especially if coupled to a thermal store when
heat is recovered when the burner is on at all times, not just when DHW is
called.