What type of shower would be the most cost efficient? Drainage and wastage systems and plumbing help, advice and answers

[longusername]

Our bathroom needs a shower. What type of shower would be the most cost efficient in the long run? We live in the UK.

We have a combi boiler that runs on gas and was installed about a year ago. We also have a box for an electric shower already fitted to the wall, as depicted in the link. We also have separate hot and cold taps on the bath.

Pictures of our bathroom with details of the inside of the electric box are here: http://imgur.com/a/tsDYO#0

I know that there are eco-friendly shower heads that will reduce the water flow and keep running costs down while still giving a good shower. Would it be possible to put an eco head on a mixer shower? Would that be our best bet?

Would be most grateful for any advice on whether to get a mixer type shower, or an electric one, principally with regard to the running costs.

[plumbbob]

The most cost effective as far as on going costs are involved would most likely be an electric shower. Even with the eco head (although you can fit further flow restrictors) a shower connected to the combi will use more water and consequently more gas to heat that water.

However, fitting an electric shower, even though the cable is there, may involve significant upgrades to your electrical installation to make it comply with current regulation. Therefore, the costs would be considerably higher than fitting a mixer shower.