On Thu, 7 Aug 2008 16:22:39 +0100, "Doctor Drivel"
wrote:

Oil combis tend to have higher flow rates than gas combis for the equiv kW.
They hold more hot water in the water jacket and this is used as a thermal
store for the instant DHW side giving higher flowrates. Many hold 30 to 50
litres of hot water.

That's interesting. If plumbing a new house would you always fit a
combi? I like the idea you only heat what you need but OTOH the
advantage of the cylinder is that you can heat with the immersion,
which might be cheaper than oil if you have economy 7.