On 19/01/2015 12:40, Ron wrote:
Would it cost more to run central heating with an unvented hot water
cylinder and system boiler or a combi boiler with no HWC?

R.
In my opinion yes. All other things being equal there will be some heat
lost from the hot water cylinder which in summer will be wasted.

This will not be the case with the combi. Unless the "non combi" boiler
is more efficient as a pure heat source (unlikely - but possible I don't
know the details of boiler design) it must cost more to run.

However pure running cost is not the only consideration for a heating
and hot water system.

--
CB