On 2007-12-21 21:28:16 +0000, said:

Thought some of you might like to know the best buys in Which?
Best combis:

Baxi Duo-tec
Potterton Gold
Vaillant ecoTEC
Vaillant ecoTEC(Larger model)

The Baxi and Vaillant were the only two boilers that met the claim of
91% efficiency.

Bottom of list we
Ideal Isar
Worcester Junior (Always thought these boilers had an over- inflated
opinion)
Potterton performa
Forgot the rest, but these boilers did not meet efficiency claim.

No open vent boilers were best buys but the top of list was the
Vaillant and at the bottom was the Potterton promax

The next boiler after the 4 best buys was a Boulter Buderus

The range of efficiencies of modern condensing boilers is in the range
from 90 - 91.5%.

SEDBUK say that where there are two boilers with 3% difference there is
a 95% confidence that one will be better than the other. They don't
say what the confidence is when the difference is only 0.5% or 1%, but
obviously less.
can measurements be made consistently to a fraction of a percent?
Seems unlikely considering the many factors involved.

Consider also the energy cost saving between 90 and 91% (assuming the
figures are reached).

A much more important set of criteria at this point becomes build
quality and servicability.