Looking for a general explanation of Solar charging (previously "Surplus only") and how Grid support works? See the Solar charging article. This article focuses specifically on why charging sometimes doesn't start, and what you can do about it.
The standardised communication protocol between an EV and a charging station (IEC 61851-1) requires a minimum charging current of 6A before an EV is allowed to start charging at all. This is not something Smappee or the charging station decides, it's a fixed requirement of the standard. In practice, this means:
- Single-phase installation: at least 1.4 kW is needed to start charging.
- Three-phase installation: at least ~4.2 kW is needed to start charging.
That's a fairly large amount of power for a solar installation to produce as surplus, especially outside of peak sunlight hours. This is why charging on Solar charging can be slow to start, or not start at all, even with solar panels installed.
1. Switch to Smart charging schedules
Schedules optimise the use of your solar production throughout the day, and will import additional power from the grid if needed to make sure your car reaches the requested charge in time. The downside: any extra solar production after the schedule has finished won't flow into the vehicle.
2. Increase Grid support
Grid support lets you reduce how much solar surplus is needed before charging starts, by allowing part of the required minimum current to come from the grid instead. It's set directly in Amps (A) in the app or Dashboard.
| Grid support setting | Minimum solar export still needed | Single-phase | Three-phase |
|---|---|---|---|
| 0A | 6A (100% from solar) | 1.4 kW | 4.2 kW |
| 2A | 4A | ~0.9 kW | ~2.8 kW |
| 4A | 2A | ~0.5 kW | ~1.4 kW |
| 6A | 0A (100% from grid) | Charges immediately | Charges immediately |
Example: with Grid support set to 4A, your car only needs 2A of solar export (~0.5 kW single-phase, ~1.4 kW three-phase) to start charging, the remaining 4A comes from the grid.
3. Adapt your charging cable
On a three-phase installation, you can detach 2 phases from the charging cable, as shown below. This lowers the minimum required power to 6A × 230V × the number of connected phases, increasing the chance that your solar production is enough to start charging.
The trade-off is a lower maximum charging speed. In most cases this is negligible: most EVs already cap around 16A on three phases (11 kW) while they could do 32A on a single phase (7.3 kW).