dennis@home wrote:

The under sink heater sitting on the shelf in my shed, doing nothing,
stores water (about 15l IIRC) and uses a 3kW heater. I don't think you
can set it any hotter than about 90C.

Cafe espresso machines also do hot water. Ours can be set from 92 to 97C,
and runs off a 13A wall socket (and water feed). However it has a reservoir
of almost-boiled water which it keeps hot (don't know the volume, but only a
few litres) and brings it back up to temperature after you've just drawn
water. I suspect it also tops up the heating on the water output too (same
machine can do steam out of another nozzle). It makes perfectly good tea.

But it's not exactly a cheap way to go...

Theo