Charge your electric car on solar power
When your panels make more than the house uses, the surplus is worth most in your own car. WattVise starts the charging when there's enough sun and pauses it when there isn't; the rest of the time the car charges by the spot price.
How it works
- Your system sends the surplus
- Home Assistant, or a script of your own, sends the current surplus to WattVise about every minute, with a personal API token.
- The car charges while it lasts
- Once the surplus has stayed above the start level (4 kW to begin with) for five minutes, the charger starts, whatever the price or plan. Once it has stayed under the stop level (2 kW) for ten minutes, it pauses. You set both levels.
- The rest of the time, the price
- At night and on grey days the charger follows the spot price or the smart plan as usual.
Good to know
- On or off
- WattVise starts and pauses the charger; it doesn't change the current. A car on three phases needs about 4.1 kW to charge at all, so while the surplus is between the stop and start levels, part of the power comes from the grid.
- Chargers with an eco mode
- Solar charging steers chargers that wait for cheap hours or follow the smart plan; a charger set to charge at once charges whatever the sun.
- Housing associations too
- An association with its own panels lets as many cars charge as the surplus feeds, about 4.1 kW each.
Questions
- Do I need Home Assistant?
- Something has to read your inverter or meter and send the surplus. Home Assistant does it with a few lines of configuration (an example is in the app, under Account → API), or any script that can send an HTTP request.
- Which inverters work?
- Any whose surplus Home Assistant or your script can read: WattVise only gets the number.
- Which chargers work?
- Every charger the app controls: Zaptec, Easee, Wallbox, Charge Amps and OCPP chargers.