3kw on a normal 3 pin house socket is a fair bit of amperage at around 13 (at the now nominal 230v.....up to nearly 14 at the minimum legally allowed, but all too common, 217 volts. Plugs get pretty warm at that level of draw. We have 3kw heater systems in some caravans on my forecourt......and we heat a few at this time of year....the 3 pin plugs and sockets get pretty warm even though they are outside! (yes we do have the blue 16 amp campsite sockets for the workshop testing....but not close enough to the show vans....so 13a 3 pin it is. Not trying to be anti EV (I'm not) or scaremongering.......just saying to check its a good plug and its going into a nice tight socket to ensure a really good connection with no arcing.