New Build house - spec for Kva supply for ehv

New Build house - spec for Kva supply for ehv

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jimbouk

Original Poster:

430 posts

199 months

Thursday 1st September 2016
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I am in the final stages of planning for building a new home, accordingly sorting out the electricity supply.

No ehv at present, but once I've cleared my new debt, do fancy a Tesla or whatever else is around then.

Considering ramping up the the KVA supply to the house in an attempt to future proof and to allow for a faster charger, I see that the pod chargers are only 7kw, should I allow for more?

Advice and thoughts appreciated!

TooMany2cvs

29,008 posts

131 months

Thursday 1st September 2016
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Are you thinking of getting three phase in, or only single phase?

Unless you're going 3ph, then all you really need do is run a sufficiently large bit of cable from the CU to wherever the wallbox is going to be. 7kw is only 32A @ 230v.

jimbouk

Original Poster:

430 posts

199 months

Thursday 1st September 2016
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Thanks. Only looking at single phase, as you say 7kw no big deal. Wondering if I should allow for a greater capacity though?

blueacid

473 posts

146 months

Thursday 1st September 2016
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I'd speculate that for much higher charging power most chargers would want to switch to 3 phase to go much higher than that.

On the flip side you might want to provision for more than the one charger, for a scenario in which you have more than one electric vehicle?

chandrew

979 posts

214 months

Thursday 1st September 2016
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The Tesla can handle 3 phase natively. It's what all new houses have in Switzerland and as such nobody seems to have wall boxes to charge their cars.

My advice from building a house is that you should put in as many points as you reasonably can. (Also put ethernet into each room as modern things like underfloor heating stop wifi getting through)

ecs

1,273 posts

175 months

Friday 2nd September 2016
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jimbouk said:
pod chargers are only 7kw
POD Point chargers? You can get them in 3, 7, 11 and 22kW - the 11 and 22kW are three-phase.

jimbouk

Original Poster:

430 posts

199 months

Saturday 3rd September 2016
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Thanks, info submitted to utility company....

As to the comment on cat5 cabling, I managed to put over 1km into my last house ! 😳

Hopefully a bit less in this one..

c2mike

427 posts

154 months

Sunday 11th September 2016
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My experience with my current house (large, recently built, with gas cook top, some electric underfloor heating, electric ovens) is that a 100A single phase supply is adequate with a 7kW charger. You need to consider the other big electricity draws in the house: electric cooker (Vs gas), electric underfloor heating (Vs hot water), etc. Consider that the 7kW car charger is taking around 1/3 of your total capacity.

Most electric cars won't support more than 7kW AC (Tesla and Zoe do), but anyway I don't see the need for more than 7kW at home. You'd have to do a lot of miles everyday and leave home early and return really late to actually need it. Latest Tesla's are limited to 16kW AC. May be useful for speedy mid-day top-ups if you have a Zoe, but longer term this won't be a problem as all EVs will get bigger batteries.
Future needs with 2 electric cars in the household, or installing other big current draw appliances (workshops, heating, etc.) could mean 3 phase is warranted.

I'm going through the same process (specifying a large house refurbishment including total re-wire - different to the house above). It will have an electric cooker (no gas), but I'm avoiding electric underfloor heating. I'm sticking with 100A and a 7kW EV charger. If the house already had 3 phase I'd do it differently, but not worth the investment to change the house supply IMO.

chandrew

979 posts

214 months

Tuesday 13th September 2016
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At the moment the i3 and the washing machine use about the same amount of electricity (in the winter the tumble drier is often the biggest usage). I have a Smappee to estimate electricity usage by appliance and it works well for simple things but less so for the more complex usage (like the hob). The washing machine / drier are the most efficient Miele ones.

The one thing I don't know how much it uses is the geothermal heater (underfloor heating). We rent that from the electricity company and it's on its own circuit - we pay a price which covers equipment, installation and electricity. Many (most?) new houses here are built with either geothermal or an air-based heat exchange system or both.

I calculated that adding solar would get a ROI after 10 years. To make most sense it probably needs a battery as well. The energy company calculators suggest given our roof-space and position we could produce 2x our energy use per year with a shortfall between mid November and late February.