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.

The CH will cost about the same.
The hot water may cost a bit more than with the combi depending on how
efficient it is at heating the water at the desired flow rate vs the
heat loss from the hot water tank. A well insulated tank may cost about
2p a day in heat loss, a poor one 25p a day.