Optiwatt times your charging to your utility's cheapest or cleanest grid hours. Its own pages don't describe charging from rooftop solar surplus. SundialEV is the better fit if you have solar and export it for a low credit: it sends that surplus to your car. 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 | Optiwatt | SundialEV |
|---|---|---|
| Solar-surplus charging | Not stated — times charging to cleaner grid hours | Yes — follows your live surplus |
| Works without a Powerwall | Yes — no home battery needed | Yes — Tesla Solar, Enphase, SolarEdge, Solis, Growatt, Emporia Vue, Sense, or the push API |
| Savings tracked against your tariff | Charging cost on your utility rate | Yes — your utility's import and export rates, looked up by zip |
| Powerwall first, then the car | Not stated | 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 — 27 EV brands (non-Tesla in listed states and provinces) and ChargePoint | 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 | Yes — time-of-use and real-time rates, 36+ utility programs | Yes — US utility rates, NEM 3.0 and net billing |
Every Optiwatt 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 Spotted something out of date?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.