"Wingedcat" wrote in message
ps.com...
Will the 79% efficiently compared to 91% actually make a big difference
to
my fuel bill?

Well with a non-condensing boiler, 79% of your gas bill is spent on
heating your house and 21% on heating the outside world. This means
that assuming an annual bill of £200 (roughly what I spend), £158 is
used productively and the other £42 goes out of the flue as waste
heat.

If you fitted a condensing boiler, if I have got my sums right you
would instead spend £158/91 * 100 which equates to £173.63 so you
would save £26.37 or about 13% a year.

If you are installing a boiler from scratch then fair play, but for me
at any rate it's certainly not worth replacing my boiler until the
current one packs up.


If you have an old cast iron boiler you will not be getting 79%, so in that
case it is worth replacing the boiler.