Hi Bryce,
A couple of colleagues and I are discussing single phase vs three phase home EV charging and trying to maximise solar charging. I’m hoping you can settle a query for us. What are the relevant differences between 1 and 3 phase home EV chargers when trying to maximise your charging off your home solar when you have a 3 phase power supply to the home.
For example, am I correct in thinking that you are better off with a single phase EV charger if your solar inverter is also single phase, even if your power supply to the house is 3 phase? And that if you mismatch your home EV charger phase with your solar inverter phase (e.g. single phase solar inverter with 3 phase home EV charger or vice versa) then it will not be best for maximising your solar usage?
Thanks,
Colin
Hi Colin – such a good question! The short answer is that in theory: yes, to maximise direct solar PV usage, charging off a single phase solar system connected to a three phase switchboard requires the charger to be on the same phase to utilise the solar output.
However, the reality is much more complicated depending on your 3 phase connection: for example if you have only 40A available on each phase (a common connection type), connecting a basic 32A charger to one phase alone will make it all but impossible to keep the rest of the home’s light and power circuits evenly spread across all phases.
Your electrician will hate trying to install it … and may even refuse to connect it.
If you do need to install a single phase charger in this situation, you would have to install a load-sensing charger that can ramp the charge rate up or down depending on the total load on that phase.
Also, assuming the charger is on the same phase as the solar, I would suggest choosing a charger that can also sense the solar output. This means the charger will ramp the charging up and down to match the solar output to enable keeping your EV running as much as possible on solar-only power.
Personally though, I would recommend where someone has 3 phase power available and a 3 phase charging capable car (which most are these days), you should install a three phase charger. This is best for balancing the grid as well as not unbalancing your switchboard.
This does mean, if the solar system is on one phase only, you will only be using one third of your solar output directly. Mind-you, if the solar system is big enough, you would likely be offsetting the other two thirds. Good for the soul to be able to say your car charges at less than a sunny day’s solar output, but perhaps not quite so good for the wallet.
An alternative option in your situation would be to install a single phase 15A outlet for car charging on the solar phase and use a portable charger that can switch between 8, 10 and 15A. You then turn it on as the solar ramps up and off when the sun goes down. (And/or switch it between 8, 10 or 15A depending on the season or how cloudy the day is to keep the charging rate under the solar output).
This latter option is very cheap to install and simple to use, but it can be a pain to remember to switch up/down/on/off at the right times!
More broadly, for people with three phase homes but yet to install solar, look at solar systems that can be spread evenly across all three phases and install a 3 phase charger with solar sensing. That way you will be able to prioritise solar power to the EV during the day as well as being a balanced load if charging when the sun is down.
Another complicating factor would be if wanting to integrate a battery into this mix. Whilst it can be done successfully (some battery systems even come with integrated car chargers and solar sensing) – that sort of scenario is very situation and model/brand specific for charger, battery AND solar inverter. As such, it needs an individually tailored solution.
Hope that helps?
Cheers
Bryce
