Alan wrote:

What is the actual saving?

That depends...

I get the impression that the hype on the
savings is comparing a modern boiler with something installed 30 years
ago and took two men and a crane to lift on to the wall.

Yup that is often the case (especially if you see overly optimistic
figures posted by dribble)!

Note however that you will get improvements in running costs simply from
upgrading the controls (i.e. better stat, fitting TRVs etc) on old
systems even without changing the boiler.

Would an average household run a condensing boiler in the most efficient

Can't see why not. Modern boilers all tend to be modulating, and hence
will do a good job of matching the actual heat output to the current
demands (better ones can modulate over wider ranges). This also tends to
mean they can keep the return temperature low enough for extra
efficiency gains from the condensing aspect of their operation.

way and is a low water content boiler of, say, 15 years age that much
less inefficient?

Grab yourself a copy of the sedbuk boiler efficiency database browser
from he

http://www.sda.co.uk/qsedbuk.htm

And you can see how various boilers compare. Note one anomaly in that
the sedbuk rating does not include the efficiency of producing hot water
(which makes sense for storage systems, but less so for combis). Some of
the condensing combis only run in condensing mode while doing heating.
(the WB Jr range for example)

As a landlord is replacing the boiler the OP will not directly have the
installation charge but how long is the break even pay-back (extra cost
of boiler plus maintenance over lower gas costs)?

Well I presume the Landlord will be paying the maintenance costs as well
so you can factor those out. There is also no reason for a condenser to
require any more maintenance than a conventional boiler of equal
complexity (assuming you he buys one of a reasonably reliable design and
not a hastiliy adapted old design bodged into looking like a condenser).

I wonder in the case of the OP the cost of repair is a £5 thermocouple
and not a boiler costing hundreds of times more?

From the landlords point of view you have to factor how much of his
time does it take dealing with problems on an old system. Even if the
repair is simple and cheap it may not be cost effective if it is
required frequently.

--
Cheers,

John.

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