If you're considering installing an EV charger as part of your home improvement plans, you may be wondering if your home has enough power to support its energy consumption.
Plus, with everything in terms of how you power and heat your home leaning towards electricity as the main source – rather than splitting the load with gas – it's not uncommon to see advice that says you should be switching to a three-phase electricity supply if you're installing an EV charger.
But, is that always the case and how do you know if you need to upgrade your supply or not? Energy expert David Hilton explains what to consider.
What is three-phase electricity?
There are two different types of electric supply that you can have to your home. The most common, single phase, is the 240-volt supply that most homes have, which has two wires – one active and one neutral, (I know there is a third wire but that is the earth, not the power) and drops to zero 50 times a second.
The alternative, three phase electricity, has three active wires so delivers a steady, constant stream of power that never drops to zero, effectively delivering three times more power.
In basic terms this means you can run more electricity-based appliances or items at any one time.
Understanding how your home uses power, and what each item draws down from your electricity supply so you figure out a total load seems like the way to establish if you will need to upgrade to a three-phase supply for an EV charger.
But, before you rush off and start reading the energy labels on all of your appliances and create some complex spreadsheet, or ask AI to try and work out how much energy your home will use, let me simplify it for you.
Do I need three-phase electricity for an EV charger?
First and foremost, it is fair to say that not all of your household appliances will be running at the same time, and definitely not flat out and full speed.
But, what is accurate, is that when we look at all the things that use electricity in the home the one that can potentially use the most energy is electric vehicle charging. And, this is why the figures need a bit more consideration, starting with assessing how many miles you do a day and how many electric cars belong to family members in the home.
As an example, if you only have two electric cars, and you each do around 40 to 50 miles a day, this means if your electric vehicle has a reasonable range then you could each plug the car in every second night and generate around 100 miles of charge per car.
I say night time, as most of the time you would set the charger to charge the car during this cheaper period – depending on who your energy provider is and what tariff you are on.
If your home has a single-phase supply, however, then this brings some limitations. You can only charge the car a maximum of 7.2kW as this is the limit on a single-phase EV charger. That equates to around 22 to 29 miles of range for every hour it is plugged in.
In my case, my electric vehicle only delivered around three miles per kilowatt, so I could charge a maximum of 132 miles on the cheaper rate overnight. But, this wasn't much use if I needed to go on a long journey as the battery capacity in my vehicle was actually 82kWh. So, it took two overnight stints to charge my vehicle to full when it was very low.
The additional problem with EV charging using a single-phase supply in a case like mine? No one else could charge during that time, potentially leaving cars without any power.
So, if you have more than two cars, or someone really needs a full charge in one go, then yes, you may find you may need to consider a three-phase electric supply. And, although it may not seem like a problem now if you haven't yet switched to electric vehicles, it is likely to be one in the future.
Can you manage without upgrading?
That said, despite the fact it may be needed in the future, in our family home we do not have a three-phase supply, and we are not planning to change to one yet.
We have a single-phase 100 Amp supply and have an EV car charger, solar PV panels, air source heat pump, double electric oven and an induction hob, plus the usual other appliances such as TV, PlayStation, washing machine and tumble dryer (we have changed to a heat pump tumble dryer which has a lower energy use).
We know that there may be some pinch points with EV charging in the future but feel that with some careful planning and management, we can avoid any issues.
One of the additional measures we have put in place to prevent problems is that the car charger we have has devices connected to it called CT clamps. These monitor the amount of energy the home is using, and if the load gets too high then the car charger simply ‘slows down’ and charges the car at a lower rate.
In summary, in my experience, if you have an average-size home, a decent single-phase electric supply and a minimum of 100 Amps, then a three-phase electric supply is not always essential even if you have a lot of electro-tech fitted to the home.
On a larger home, however, the three-phase supply becomes more important and can add a lot more convenience, especially with EV car charging, as well as reducing the need for appliance management.
The size and value of the home combined with the cost to install a three-phase supply, plus your personal wish for convenience, and how many cars you need to charge, will likely be the deciding factors. For a new self build, it would certainly make sense, but for a home renovation, you may be able to manage with what you have, for now.
