Friend has been notified by their Freeholder that the communal Boiler for heating and H/W will need upgrading at a cost of 80-100K per apartment !! They are going to get many quotes and options themselves as this seems extortion ! Or Each flat can fit their own. But Must be Electric . Its a tiny flat that only has 2 rads fed from main boiler .The other 3 are super efficient German heaters that are ok and dont cost a fortune to run . So they need water for bathroom (bath combined stand up shower ) and kitchen . What electric options are worth considering ????? There is NOT a lot of room! SO no chance of a huge tank etc etc .Needs to be a little more " instant "