SAJ + Fronius Wattpilot

What Zerofy can do with SAJ and Fronius Wattpilot

In practice

• Zerofy adjusts the charging current of your Wattpilot but doesn’t switch phases. On a three-phase connection, solar charging needs at least about 4.1 kW of surplus (6 A × 3 × 230 V); on a single-phase connection about 1.4 kW.
• A typical SAJ home system (3–10 kW) needs a sunny midday to reach the 4.1 kW three-phase minimum. Wired single-phase, the charger starts from about 1.4 kW but charges at no more than about 3.7 kW.
• Zerofy gets new SAJ data every 5 minutes and adjusts accordingly. A minimum runtime and an activation threshold in Autopilot keep passing clouds from interrupting charging.
• Zerofy also shows your SAJ battery, so you can see whether surplus goes into the battery or into the car.
• If your car is connected to Zerofy too, turn on Autopilot for either the car or the charger, not both.
• In its own surplus mode the Wattpilot starts at 1.38 kW on one phase, adjusts in 0.23 kW steps and switches to three phases above 4.14 kW, where it steps in 0.69 kW; the switching level can be changed in the app. Via OCPP, Zerofy sets the charging power but not the phases, so the minimum is 6 A: about 1.4 kW single-phase or 4.1 kW three-phase.

What SAJ and Fronius Wattpilot offer on their own

SAJ: SAJ’s Caro wallbox (7 kW, 6–32 A, or 11 kW, 6–16 A) can charge from solar and supports OCPP 1.6J. The manual says PV charging needs an SAJ H2+B2, HS2, AS2 or HS3 storage system plus the eManager.

Fronius Wattpilot: The Wattpilot’s own PV surplus charging needs a Fronius inverter (GEN24, Verto, or SnapINverter/IG with Datamanager 2.0) with a Fronius Smart Meter at the feed-in point, talking over the Solar API in the same network. Other inverter brands only work with an extra Fronius Smart Meter IP or Datamanager Box 2.0 plus Smart Meter; the Wattpilot then also appears in Fronius Solar.web.

Zerofy connects the two: it reads SAJ production and controls your Wattpilot to match, together with your other devices in one app, with dynamic tariffs and forecast-based Smart mode.

Setting up SAJ and Fronius Wattpilot in Zerofy

1. Connect SAJ

Zerofy reads your plant from the SAJ cloud: you add Zerofy as a developer in the Elekeeper app and then enter your Plant ID in Zerofy.

1. In the Elekeeper app, tap ••• and open Plant Management.
2. Under Developer/Partner, paste the Developer ID shown in Zerofy and confirm access.
3. Copy your Plant ID from Plant Management and paste it into Zerofy.

Good to know: How fresh the data is depends on how often the SAJ cloud updates. For the battery, Zerofy supports forced charging but not switching the battery mode.

Step-by-step guide for SAJ

2. Connect Fronius Wattpilot

The Wattpilot connects to Zerofy via OCPP 1.6J; you enter the connection details from Zerofy in the Solar.wattpilot app.

1. In Zerofy, add a Fronius Wattpilot and copy the OCPP connection details.
2. In the Solar.wattpilot app, go to Internet → OCPP and enter the details.
3. Save and wait until the status shows the connection is established.

Step-by-step guide for Fronius Wattpilot

3. Turn on Autopilot

In Zerofy, open your Wattpilot, turn on Autopilot and choose Solar – or Smart to also use dynamic tariffs and forecasts. Set the priority, activation threshold and minimum runtime.

Dynamic tariffs

Zerofy can also run your Wattpilot on dynamic electricity prices (EPEX Spot or Nord Pool, e.g. Tibber or aWATTar) or on a fixed time-of-use tariff. Smart mode combines those prices with forecasts of your household consumption and your SAJ solar production.

Learn more about Smart Mode

About SAJ and Fronius Wattpilot

SAJ – SAJ (Guangzhou Sanjing Electric) is an inverter maker from Guangzhou, China. Homes usually have the H2 hybrid inverter with B2 battery or the HS2, HS3 or AS2 all-in-one storage systems; the eManager unit and the Caro wallbox tie them together. Monitoring app: Elekeeper.

Fronius Wattpilot – The Wattpilot is the EV charger of the Austrian inverter maker Fronius, built for solar charging with automatic 1/3-phase switching and surplus charging from 1.4 kW. The Flex has LAN and Wi-Fi, a §14a input and a Pro version with MID and Eichrecht; it is mainly sold through installers. Products: Fronius Wattpilot Flex Home, Wattpilot Flex Pro, Wattpilot Go, Wattpilot Home.

Manufacturer information last checked: October 2026.

All devices that work with SAJ