Water – Separate or combined boiler and hot water heater

I'm in the UK, we got a new recently due to the rebate recently offered on really old boilers.

If you get a decent boiler it provides savings because it is more efficient. They are called "condensing" combination boilers - the condensing action reclaims lost heat, I think.

We got a Vaillant, who also make the glow-worms. Never heard of Ferroli. And yes we get decent hot water pressure. I would check with a few plumbers/gas engineers, just get a few quotes, and also check the boiler specification for max flow rate.

Couple of tips if you do get a new boiler be sure to specify exactly where the pipes go (if you change location), get one of the remote controls (very handy, and allows you to put boiler in loft), and also specify exactly how you want the magnaclean device fitted (collects sludge from central heating). Ours is unfortunately very prominent - we need to move it.

Also, we went for a really big powerful boiler, so more than enough water but tbh probably a bit too big for our house: bigger may not necessarily always be better.

I'd only get vaillant, glowworm, or worcester-bosch, btw.

Without natural gas or propane, your only source of heat is electricity. Electric tankless water heaters would probably require a new circuit to be run. Here's a table of typical power and wire requirements:

http://www.rheem.com/documents/rte-13-tankless-electric-spec-sheet

The smallest unit they recommend for a shower is the RTE13 which takes 13 KW or 54A@240V. This requires #6 wire. If your incoming temp is 40F and desired out temp is 110F, you need 70F of temp rise and the RTE13 will provide 1.27 GPM.

Many people think they want tankless because the mfg tell them tankless is more efficient. There is some truth to this for gas fired water heaters but in the case of electric water heaters, the difference in efficiency is very small.