Roger wrote:

the few cases where new will produce a saving. However the chances are
that as condensing boilers need larger radiators to allow them to
operate at their most efficient you would need to factor in the cost of
the whole of a new heating system or accept that your savings will not
be as great as sedbuk predicts.

I am not convinced that is going to be true most of the time. You need
to consider that modern boilers are modulating and will adjust their
flow temperature so as to achive good efficency regardless of radiator
sizing. The only time this will not be true is when the outside
temperature is so cold that you need to run a higher flow temperature in
order to get the house warm enough.

However, that does not change the sums much, so you still need to do
them to work out if there is any advantage to a premature replacement.

--
Cheers,

John.

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