Is there anything out there like a PV, inverter, immersion kit - i.e. the immersion is all the PV panels power? We have four hot water cylinders between the house and cottages and in the summer when there is no need to burn oil for central heating something like this could be a simple way to keep the heat topped up on the water? I've searched but dont really know if they exist or at what cost? I can see me doing this rather more rapidly than a more extensive installation if its cheaper/simpler than a full 'power the house and feed the grid' type installation.