Charging your EV on surplus solar with SolarEdge: options and gotchas
More and more solar owners are on export plans that pay far less than electricity costs to buy: net billing in California (PG&E, SCE, SDG&E for systems installed since April 2023), shrinking feed-in tariffs elsewhere. If your exports earn a fraction of your import rate, midday surplus is worth more in your car than sold back cheap. (Full retail net metering? This matters a lot less.)
Disclosure: I build one of the options below.
Check for a consumption meter first. Surplus charging needs household load, not just production. If your SolarEdge monitoring shows only what the panels make, there's no consumption meter on the system. Options: have an installer add one (best fix), add a home energy monitor like Emporia Vue, or use a tool that estimates load — that last one is a guess and won't react when the AC kicks on.
Your options:
- SolarEdge's own EV charger with its solar charging mode. Simplest if you're buying a charger anyway and you're all-SolarEdge.
- DIY with Home Assistant or evcc. Both can read the inverter locally (Modbus) and control Tesla or OCPP chargers. Free and flexible if you maintain it.
- An app. I build SundialEV, which reads SolarEdge and adjusts charging amps to follow the surplus.
Worth checking first: what your exports actually earn. This calculator pulls your utility's export and import rates (US, by zip) and shows the monthly gap: https://www.sundialev.com/calculator?utm_source=reddit_organic&utm_campaign=solaredge
Happy to answer questions about any of these, not just mine.