I have a single storey cottage and consequentially have very little
head to drive a shower. There's an extension that has the shower in
it, currently electric.

I'm having PV panels fitted so it seems sensible to use the excess
electricity to heat the tank for a 'proper' shower.

The shower is some 8m from the tank with a 15mm HW feed for the a
basin in the shower room and the kitchen. If that pipe is pumped, and
including the shower, will that pipe be bigger enough?

Thanks in advance
Rob