A solar charger detects excess solar at the home’s supply point, not at the panels. A current sensor fitted where the home meets the grid watches power flowing in both directions: when the home starts exporting — sending power out — the exported amount is the surplus, and the charger raises or lowers the car’s charging to track it. The charger never measures the roof. It measures the boundary, and everything the house does moves that reading.
Key Takeaways
- Excess solar is detected at the supply point: export is the surplus, and the charger tracks the export.
- The reading is production minus the house’s own use, so house loads and batteries move it as much as clouds do.
- Detection needs both a sensor and a charger that acts on it — a system specification, not a label.
- No EVDANCE listing states surplus sensing or includes a supply-point clamp.
Surplus Is a Subtraction, Not a Panel Reading
The surplus is what is left of the panels’ output after the house has taken its share: production minus consumption, worked out continuously by the direction of flow at the boundary. That is why two homes with identical roofs show different surpluses at the same moment, and why a session can slow at noon under a clear sky — the panels were producing, but the house was using the power first. Our guide to solar panels and EV chargers sets out the wider picture; the point here is that “excess” is defined at the meter, not on the roof.
| What changes | What the sensor sees | What the charger does |
|---|---|---|
| A cloud crosses | Export shrinks, or flips to import | Lowers the car’s rate, or pauses the session |
| A kettle or oven switches on | The house load takes the surplus first | Drops to the smaller surplus that remains |
| Full sun, house idle | Export at its largest | Raises the rate toward the surplus |
| A home battery is charging | The battery takes surplus before it can be exported | Sees less at the boundary — the car waits its turn |
Two Ways the Reading Reaches the Charger
On some systems a clamp sensor on the supply cable reports the flow directly to the charger. On others the figure comes as data from the solar inverter or a home energy meter that already measures the boundary. Either way, the number is the same net flow, and the charger needs both halves of the arrangement to follow it: the sensor, and a charger built to act on the reading. A sensor on its own changes nothing, which is why surplus detection is a system specification, not a charger label.
Checking the Detection Is Telling the Truth
- Compare the two apps. Your inverter app shows production and export; the charger app shows the rate it has chosen. At the same moment, the chosen rate should make sense against the export figure.
- Run the kettle test. Switch on a heavy household load and watch the session respond. A charger that drops its rate when the kettle boils is reading the boundary correctly.
- If the readings persistently disagree, the question belongs to the installer or the maker: the sensor’s position decides what its reading means, and a clamp in the wrong place reports the wrong flow.
EVDANCE and Surplus Sensing, Plainly
No EVDANCE listing states surplus sensing, and no EVDANCE charger is sold with a supply-point clamp in the box. The EV-ACS3210E states an app with energy monitoring — of the charger’s own sessions, which is a different measurement from the home’s export. If surplus-following is the feature you are buying for, it is a written-confirmation item before purchase, for our range as for any other; the current range is on our residential EV charging page.
Frequently Asked Questions
Can the charger see how much my panels are producing?
No. It sees the net flow at the boundary. Panel production is the inverter’s number; the charger’s number is what remains after the house has taken its share.
Why did charging slow down at noon on a sunny day?
Something in the house was using the surplus first — cooking, heating water, charging a home battery. The sensor was reporting honestly; the surplus genuinely shrank.
Does the same sensor do anything without solar panels?
Yes — the same boundary measurement serves load management, keeping the house within its supply limit, as our explainer on dynamic load balancing describes. But with no generation there is no surplus to follow.
Related Reading
- Solar Panels and EV Chargers: How to Charge Your Car With Sunshine
- What Is Dynamic Load Balancing, and Why Does Your Wallbox Home Charger Need It?
- Smart Charging and Time-of-Use Tariffs: How Scheduling Cuts EV Charging Costs
- What Size EV Charger Can I Have at Home? Panel Capacity Explained
