OverflowEV and SundialEV both charge your EV from surplus solar, through a Tesla or an OCPP wallbox. SundialEV is the better fit when your savings depend on a US utility's export rate: it looks up your utility's rates by zip. If your solar was interconnected after April 15, 2023 (NEM 3.0), exports earn a fraction of retail — 4.5¢ per kWh against about 35¢ to import on PG&E (rates as of July 2026), so every kWh your car absorbs instead is worth far more.
| Feature | OverflowEV | SundialEV |
|---|---|---|
| Solar-surplus charging | Yes | Yes — follows your live surplus |
| Works without a Powerwall | Yes | Yes — Tesla Solar, Enphase, SolarEdge, Solis, Growatt, Emporia Vue, Sense, or the push API |
| Savings tracked against your tariff | Yes — savings vs. grid charging, at rates you enter | Yes — your utility's import and export rates, looked up by zip |
| Powerwall first, then the car | Not stated (has “home battery priority”) | Yes — solar goes to the car once the Powerwall reaches your priority level |
| Sell-at-peak window | Not stated | Yes — a daily window where solar exports instead of charging |
| Non-Tesla EVs | Yes — OCPP 1.6 wallboxes | Any EV on a Wallbox Pulsar Plus (OCPP) or Emporia charger; Ford battery level (beta) |
| Cloud or self-hosted | Cloud | Cloud — iOS, Android and web apps |
| US utility rates | Manual time-of-use rates; no US rate database stated | Yes — US utility rates, NEM 3.0 and net billing |
Every OverflowEV cell links to the page it came from, checked September 26, 2026. “Not stated” means their pages don't say either way. Spotted something out of date? Email support@sundialev.com and we'll fix it.
Enter your zip and the calculator uses your utility's real rates.
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Works to utilize my solar to charge my car! I have it set up so I don't draw from the grid to charge my car (free fuel!)
ChronoVII · App Store
Provides an amazing amount of control for how and when you charge your vehicle. Support is also very responsive.
Mark A. Hartman · App Store
This app makes charging for the most part easier especially if you only want to charge on excess solar
ecyka2000 · App Store
SundialEV charges from your solar surplus automatically.