You Have Solar But The Car Still Charges From The Grid

What's happening?

A charge point does not know anything about your solar unless it has been made to. On its own it is a fixed load: plug in, draw 32A, stop. Matching it to generation needs two things the standard install does not include. A current sensor on the incoming supply, so the unit can see how much of your generation is spilling out to the grid rather than being used, and a charge point capable of modulating its output continuously down to a low current — because solar in the UK moves constantly and a unit that can only go on or off will chase clouds and stall. Only some units do this. Where they do, the unit can be set to charge only on surplus, to blend surplus with a minimum grid draw, or to ignore solar and charge at full rate when you need the range. The reason this matters financially is that surplus you export earns whatever your export tariff pays, while surplus you put in the car displaces electricity you would otherwise have bought.

What usually causes it?

• A charge point with no solar or surplus-matching capability, so it only charges at a fixed rate
• No current sensor fitted at the incoming supply, so the unit cannot see the export
• Sensor fitted on the wrong side of the meter or the wrong way round, so surplus is never detected
• A car with a high minimum charging current, so a small surplus is never enough to start a session
• Solar and charge point installed by different firms with no discussion of how they would work together
• A battery storage system that soaks up the surplus first, leaving nothing for the car

When should you call an EV charger installer?

Call an installer where the unit supports surplus charging but no sensor is fitted, where the sensor is in place but the readings look wrong, or where you want to know before buying whether a particular charge point will work with your existing inverter and battery. If solar and storage are being installed at the same time, get the two installers talking, because the order in which surplus is offered to the battery and the car is a design decision.

What will the EV charger installer actually do?

• Confirm the charge point model actually supports surplus or solar-matched charging
• Fit and orientate a current sensor at the incoming supply so import and export are measured correctly
• Commission the charge point's surplus mode and set the minimum current it will run at
• Set the priority between battery storage and vehicle charging where both are present
• Verify with the generation monitor that export falls to near zero when the car is charging on surplus