How many kVA should I spec?

[flanagaj]

Ok, I appreciate this ideally requires an electrician, but I am hoping that someone on here can give me an idea.  4 bedroom detached 200m2 two storey property with underfloor heating upstairs / downstairs, EV charging point and induction hob.  Aside from those high consumers, there isn't anything else outside a typical domestic property.  I was thinking of a specifying 20kVA.  Does that sound about right? 

[JohnMo]

Just a big standard 100A single phase, job done.

 

Shouldn't need any more than a 6kW heat pump, that will pull about 1400W max during start up so just a minute or so. Induction hob and charging is rarely done at the same time.

[crispy_wafer]

if you are speaking to the dno, they may well be fitting 3ph cutouts as standard now, you'd probably only need 100A for domestic use.  However as time goes on you may end up with electric vehicles, faster charging may be a nice to have, so being able to pull from the 3 phases would benefit

[Nickfromwales]

Rapid EV charging is the obvious advantage, but if you’ve only a modest home it’ll still possibly need a second phase if you want more than one EV charger. 
 

It’ll become commonplace for homes to have more than one EV I expect, so this is defo a big consideration for future proofing.

[Stu789]

I recently made an application for new-build connection estimate with National Grid with very similar consumption to yours - they proposed 3 phase 60Amp per phase.

They called me to discuss, we agreed desktop estimate given we are at pre-app stage and then they emailed details and called to followup - all very helpful.

A little more cost for 3P CU but fast EV charging, greater draw and sell-back to grid to/from batteries and 3 phase hybrid inverter is a very small price premium & EV chargers are mostly common model for 1/3 phase.

 

[Nickfromwales]

2 hours ago, Stu789 said:

I recently made an application for new-build connection estimate with National Grid with very similar consumption to yours - they proposed 3 phase 60Amp per phase.

They called me to discuss, we agreed desktop estimate given we are at pre-app stage and then they emailed details and called to followup - all very helpful.

A little more cost for 3P CU but fast EV charging, greater draw and sell-back to grid to/from batteries and 3 phase hybrid inverter is a very small price premium & EV chargers are mostly common model for 1/3 phase.

 

Plenty of argument to go 3ph these days, but having a decent amount of solar + batteries does become more useful if you can import and export x3 over the same period of time. 

[flanagaj]

A quick update on this.  I spoke to them and they also proposed 3 phase.

[LnP]

This demand calculator might help https://www.ssen.co.uk/our-services/tools-and-maps/demand-calculator/

[SteamyTea]

18 hours ago, Stu789 said:

new-build connection estimate with National Grid

Assuming that is the company previously known as Western Power, then I think it is standard policy to fit 3 phase by default.

 

3 phase does give you the advantage of connecting up to 16A of PV on each phase, so 11.5 kW_p without special permission.