Yes, electric is a lot more expensive to heat water and house than gas. Our friends have electric central heating and their bills are astronomical, I am talking hundreds of pounds every quarter. If the house has a gas supply I would highly recommend you change it to gas. I know the initial cost will be expensive, but I am sure you would benefit from it very quickly moneywise. You could have a combi gas boiler instead and that would get rid of the tanks for you. Speak to plumber who could give you advice and a quote.