Single or three phase power for new build? Thinking of car chargers

Forums › Home Workshop DIY › Single or three phase power for new build? Thinking of car chargers

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Batman

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#2756897 8-Aug-2021 21:08

lyndondrake:

Batman:

if a house is $ 1 million dollars, what is another 10k?

I still have to find the cash, but yes I agree more or less. It's one of those things which can't be deferred until later in any sensible way and which future-proofs the house in significant and helpful ways.

it will massively increase your house value if the future buyers would own a couple of EVs

Scott3

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#2756922 8-Aug-2021 23:05

lyndondrake:

This is awesome - just the kind of detail I needed. The only difference is that Vector are offering us 32A, 60A, or 100A fuses, as well as the 1- or 3-phase choice (& we're in Auckland).

Interesting. That is a more diverse range of options than I expected, which adds a little complexity to the decision.

In particular the availability of a 100A single phase offering (cira 23kW) provides a decent option to consider. Gets around the issues with the common 60A single phase connection being a bit borderline in capacity for an all electric home, potentially avoiding the need to jump to three phase.

My gut feeling is that 100A single phase should be enough to cover the power needs of a fairly typical house, even with multiple EV's (as long EVSE's with a capacity sharing feature were selected). - And likely cheaper than three phase.

That means the justification for spending more money three phase pretty much comes down to:

Running three phase requiring stuff (workshop machinery, massive central air / pool heat pumps, big welders, 11kW/22kW EV chargers)
If the power demand of your house is going to be abnormally high due to a combination of stuff like: Spa pool, electrically heated swimming pool, dual ovens in kitchen, 5+ element induction hob, dual tumble dryers (or a 20A commercial style dryer), kiln, sauna etc.
If you didn't want to go with EVSE's that can manage capacity.

Personally I would still be really keen on 3 phase power, but that is just me.

On the EV topic, There have been comments that 7.2kW (32A single phase) charging is pritty much fast enough to charge current EV's overnight.

This is pritty much true. A 64kWh Kona with 484km WLTP rated range, can charge on this power in 9:15, and even something like an audi etron (380-452km WLTP range depending on version) with a 95kWh battery pack would charge in something like 14 hours at this speed. (noting that starting from absolutely zero is unlikely, so an hour or two could be knocked off those times.

But very hard to predict where this will go in the future. The Nissan leaf was launched in 2011 with a 24kWh (total not usable) battery pack, and has since become available in 30kWh, 40kWh and 62kWh versions (the latter is the e+ version launched in 2019). That e+ has 2.6x the battery capacity of the 2011 lead that was only launched 8 years prior to it. Hard to say when this kind of battery capacity growth will end. Should also note that most current EV's are either fairly small or aerodynamic. Getting a decent range out of something like a electric land-cruiser 200 on all terrain tires will potentially require twice the battery as an efficient hatchback / sedan.

With a 100kWh+ pack, 11kW charging would be looking a lot more attractive than with a 64kWh pack. (but conversely with a longer range the odds of needing a full charge overnight drop).

Regarding instant electric hot water. Interesting thing to consider.

Pluses

Save standing losses (note this is material isn't massive, should be under 2.2kWh/day on a 300L MEPS cylinder - $145 a year on my power rates - or less for smaller cylinder)
Save space
Potentially have smaller instant units at common point sources like handwashing basins, meaning less time waiting for the hot to turn up.
Infinite hot water

Negatives

Loose access to slightly discounted "controlled" power prices based on the lines companies being able to shed your cylinder at peak times.
Use a heap of power. For example the 28kW unit here https://www.stiebel-eltron.co.nz/dhe-au-instantaneous-3-phase-water-heater nees 40Amps 3 phase power. Might mean you need the 100A 3 phase option rather than the 60A, as it would only leave 20A per phase available if the hot water was running flat out.
Despite the above, relatively weak compared to the gas instant models we are used to. For example a Rinnai INFINITY® EF26 (advertised as 26L/min at 25 degree rise) has an output of 44.5kW. - Scaling this means the 28kW electric unit is roughly equivalent to the smallest gas units advertised at 16L/min. Not enough to run two showers at 9L/min at the same time...
Can't have one of those recirculating loop setups for quick hot water.
If you get solar in the future, dumping excess mid day production into a big dual element cylinder (bottom element on a solar controler, top on normal (ripple controlled supply) so you don't run out) is considered ideal.

If you had ampal electrical capacity, and some remote taps (i.e. if kitchen was far from water heater), an instant water heater dedicated to the kitchen tap could be considered regardless of what is doing the main hot water for the house.

Heat pump hot water is something that could also be considered. Similar to space heat-pumps. +$3000 or so capital, but 1/3rd the power use.

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#2756926 9-Aug-2021 02:32

Batman:

if a house is $ 1 million dollars, what is another 10k?

It's $10k. You have to pay it back, plus interest.

$10k is a nice holiday.

Handle9

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#2756927 9-Aug-2021 02:33

Batman:

lyndondrake:

I still have to find the cash, but yes I agree more or less. It's one of those things which can't be deferred until later in any sensible way and which future-proofs the house in significant and helpful ways.

it will massively increase your house value if the future buyers would own a couple of EVs

I bet it'll make zero difference. It's a niche thing that won't effect many people whatsoever.

richms

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#2757014 9-Aug-2021 10:43

I am looking into the same thing at home when it comes time to redo the wall with the meter and breaker panel on, as last time I looked they had deemed the pole outside unsafe to climb so wouldnt upgrade without me replacing it (yet it was fine for them to climb to replace their stupid fuse at the top)

Since then they have replaced the pole so I should be good to go now, but I have been told to do it sooner rather than later as they will start to be wanting a lot more money on the upgrades to go towards them replacing their under rated for all the infill housing transformers in the streets - may be too late now.

Check if they want to ping you more for the bigger supplies to upgrade their own equipment. With the transformer in the street labeled 150kva I dont see how they can attach houses to it that can take 75+ kw without upgrading that.

Richard rich.ms

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#2757084 9-Aug-2021 12:42

So my house is split into 2x dwellings with 2x kitchens \both having stoves/ovens/microwaves and 7 bedrooms and 3 bathrooms in total. Everything is electric including hot water, ovens, stoves and we have 2x water pumps for potable/non-potable and charge an EV overnight at 8A. Never once have we overloaded a single phase 63A breaker.....

Do you really need to charge EVs that fast? planning to drive 100s KM per day? Even 8A charger overnight is easily enough for the daily run of ~20KM.

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Scott3

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#2757086 9-Aug-2021 12:42

Handle9:

I bet it'll make zero difference. It's a niche thing that won't effect many people whatsoever.

Currently EV's are niche.

But NZ could potentially follow the UK and ban non plug in cars from 2030, and non pure electric from 2035... That latter date is only 14 years away. (I think we will lag the UK by 5 or so years).

Of course trying to predict the future is rife with issues. 25 year's ago future proofing your house for "computers" meant having a phone jack in every room...

mdooher

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#2757101 9-Aug-2021 13:19

10k?... the only difference for installation is a 3 core cable instead of single core and a 3 pole main switch

If the extra charge is from vector, just do as someone else said and run a 3 core main cable from your boundary. If you are lucky you will end up with 3x185 to your connection anyway

Matthew

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#2757195 9-Aug-2021 14:36

Scott3:
Handle9:

I bet it'll make zero difference. It's a niche thing that won't effect many people whatsoever.

Currently EV's are niche.

But NZ could potentially follow the UK and ban non plug in cars from 2030, and non pure electric from 2035... That latter date is only 14 years away. (I think we will lag the UK by 5 or so years).

Of course trying to predict the future is rife with issues. 25 year's ago future proofing your house for "computers" meant having a phone jack in every room...

EVs aren't niche but having a 3 phase supply is. A fair chunk of the population has no idea what it is. It's not something that will move the needle for most consumers.

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