Hi,Cant help with the actual cost,but I had a similar conversation/request with a man called Enis.He is a builder etc, speaks excellent english and has an office close to the bus stop at the Seryl hotel.It threw up a couple of points which were,the tanks out here were relatively thin and could rupture flooding the house.Plus,if the tank was below the solar panels you had to have a pump installed which would increase the electric bills.As we use gas for hot water and hob cooking which is quite economical and not subject to electrical cut offs we didn't proceed.Hope this is of some help.