be weary of the throughput. I fitted two 3 kW Redring (13A) units some years ago in two outside toilets. The water flow was just a very fine spray and absolutely pathetic even for hand washing. If you wanted to fill one sink (let alone two) I seriously think it would take half an hour.
It depends how much water you want and how long you want to run it for really. Check the manufacturers specification. This is the sort of thing I'm referring to.
http://www.tlc-direct.co.uk/Main_Index/Water_Heating_Index/Instantaneous_Water_Heaters_1/[/QUOTE]
I know the ones you are on about the fine spray they give off is next to useless, i was trying to steer the op towards the 5ltr above / under sink ones with the large swan neck spouts, rather than them piddly ones. . . A bit more money to splash out on but worth the extra ( pardon the pun ).