Efficiencies of electric showers with hot water supplies?!

[Greg:]

What do you think of showerslike:
http://www.mirashowers.co.uk/onlinecatalog/pdf/p3821_4.pdf
with the above PDF stating
2.2.The mains supply must be 230–240 V at 50 Hz connected to the appliance
viaa double pole switched 3 Amp fused connection unit (not supplied) with a
minimum 3 mm contact separation gap in each pole.

obviously a typical electric shower with a single cold water feed operates with reasonable efficiency in a similar way to an electric kettle with a pump.


How does this compare to showers with hot water feeds that operate eitherin connection to a water storage tank or a combi boiler?

 

[kingeri]

Electric heating is pretty much 100% efficient as all the energy is converted to heat and none of that heat is lost. Gas boilers dump some of their heat out of the flue so hence the 90% efficiency or whatever.

However, as electric is so much more expensive than gas per comparable unit, it is still usually cheaper to use gas for heating. Electric showers are used more for convenience I dare say.

 

[Fin170]

Electric showers are used more for convenience I dare say.

Handy when you on bottled gas.....such hell cometh when gas run out in middle of shower....

 

[Greg:]

Thanks kingeri. I guess its a tricky balance and, at present, my suspicion is that the economics may get close to that. Gas may be cheaper but some of the heat of the water will also leak heat on the long and winding road from boiler to shower and, in the summer, that heat would be completely wasted.


My guess is that a major factor related to shower installations in refurbs would be the comparative cost of a making a hot and cold connection for the shower (which would be already in the bathroom) vs the cost of adding new circuits with 6 or 10 mm2 T&E from the DB (which is less likely to be situated in the bathroom).


Any other judgements on running costs ... or the potential effects of bottled gas?