Short answer
It can, and it is called surplus charging or solar charging. You need a meter in the meter cupboard that sees how much you are feeding back, and an EV charger that can adjust its current in steps. The charger then charges only with the surplus. Bear in mind that charging below about 1.4 kW is not possible: that is the lower limit of the charging protocol.
Who this article is for Anyone with panels and an electric car. I do the set-up together with you; fitting the metering module is installation work.
What surplus charging is
On a sunny day your panels produce more than the house uses. That surplus normally goes into the grid. With surplus charging it goes to the car, exactly as much as is left over. If the washing machine suddenly draws power, the car charges more slowly for a while.
That requires two things:
- a meter in the meter cupboard that sees what goes in and out
- an EV charger that can regulate in steps, from 6 to 16 amps
That is the same metering module that is also used for load balancing. If you already have that, it is usually just a setting.
The lower limit of 1.4 kW
The charging protocol between charger and car starts at 6 amps on one phase, about 1.4 kW. Below that limit it cannot charge; the charger then has to pause. So on a cloudy day with 800 watts of surplus nothing happens.
Some chargers solve that by waiting a while and then charging a block. Others switch between single-phase and three-phase, so they can carry on with little sun. The latter is handy but not every brand can do it.
Three modes you can usually choose
| Mode | What it does | Who for |
|---|---|---|
| Solar only | charges exclusively with surplus | those who rarely need the car |
| Solar with top-up | solar first, topped up to a minimum | most people |
| Fast | full power, regardless of the sun | when the car has a long way to go tomorrow |
In practice the middle one is the best choice.
In practice the middle mode is the best. You get the most out of your panels, but you are never left with an empty car.
What it gains you
Every kilowatt hour you put into the car yourself is a kilowatt hour you do not have to feed back and buy back later. What that is worth depends on your contract and on the feed-in charges your supplier applies. At current rates the difference is big enough to be worthwhile, especially if the car is at home during the day.
What the installation needs for it and what it costs, I look at in your home. Often the meter cupboard is already prepared because a meter was fitted with the EV charger.
From my own work
A customer in Beek insisted on charging only on his own solar. In winter the car sat idle for days because there was never enough surplus. I set it to solar surplus with a floor: every night at least up to thirty per cent at the regular rate, the rest during the day on solar. That is the setting most people end up with.
When to call an electrician
- You have panels and an EV charger but they do not work together
- You want to know whether your charger supports surplus charging
- There is no meter in the meter cupboard
Usually it is a matter of adding a metering module and changing a setting. Call +31 43 204 18 26 or request a quote.
Frequently asked questions
Can my car charge on solar power only?
It can, but below about 1.4 kW it cannot charge. In winter the car may then sit idle for days; that is why most people choose solar with a floor.
Do I need a special EV charger for this?
The charger must be able to regulate in steps and work with a meter in the meter cupboard. Most modern wallboxes can do that.
Does this also work with a home battery?
Yes, but then you do decide what gets priority: fill the battery first or the car first. That is a setting I choose together with you.
Further reading
A dynamic contract and a home battery: is it worth it
With a dynamic contract the battery can charge when electricity is cheap. That works, provided you let it be controlled automatically.
The net metering scheme is ending: what changes for my panels
Your panels keep generating just as much. What changes is the value of the electricity you feed back.
Feed-in charges: why you pay for your own electricity
More and more suppliers charge for feeding your solar power back into the grid. Your bill shows what that costs you.
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