Hoymiles + Viessmann

What Zerofy can do with Hoymiles and Viessmann

In practice

• Hot water is the simplest heat store: Autopilot can use the hot-water boost of your Viessmann heat pump to heat water in hours with surplus.
• Zerofy can also change the room temperature of your Viessmann heat pump, so space heating can shift into sunny hours.
• A heat pump draws roughly 1–3 kW while running. A Hoymiles balcony system covers only a small part of that, a rooftop system (Hoymiles systems range up to 10 kW) much more on sunny days.
• Zerofy gets new Hoymiles data only every 15 minutes, so the heat pump reacts to clouds with some delay. A slightly higher activation threshold and a minimum runtime in Autopilot keep it steady.
• Autopilot uses Viessmann’s one-time hot-water charge. Because Zerofy can also set the hot-water temperature for Viessmann, you can choose how much surplus the cylinder stores: a higher setpoint holds more energy, at the cost of a somewhat lower heat pump efficiency.
• The Zerofy integration for Viessmann is in beta.

What Hoymiles and Viessmann offer on their own

Hoymiles: On the three-phase HiOne all-in-one storage system (G3), Hoymiles has a dry contact (DO1) for SG Ready heat pumps, but the manual (January 2026) lists heat pump control as “coming soon”. Hoymiles microinverters have no heating control.

Viessmann: Viessmann’s Energy Management on One Base links Vitocal heat pumps, the Vitocharge VX3 battery, the Viessmann Charging Station and hot-water tanks, using an E380CA energy meter; ViCare then shows self-consumption and autarky. Third-party inverters are brought in through the Solar-Log Base Vi gateway, with compatibility per Solar-Log’s component database.

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

Setting up Hoymiles and Viessmann in Zerofy

1. Connect Hoymiles

Zerofy connects to the Hoymiles S-Miles Cloud with your S-Miles account and reads your PV production.

1. If your installer hasn’t set up your plant yet, register it in the S-Miles Installer app (use DIY mode if you install it yourself).
2. In Zerofy, add an inverter, choose Hoymiles and log in with your S-Miles credentials.
3. Use Autopilot (Solar Mode) to switch devices on solar surplus.

Good to know: Zerofy reads PV production only from Hoymiles, not grid meter or battery data, and stores the power history in 15-minute steps (5 minutes for most other brands).

Step-by-step guide for Hoymiles

2. Connect Viessmann

Zerofy connects to the Viessmann cloud with your Viessmann (ViCare) account and shows a Space Heating and a Hot Water Tank device; you can adjust room and hot-water temperature, and Autopilot triggers the hot-water boost.

1. Check that the system runs on Viessmann One Base or has an Optolink interface with a Vitoconnect OPTO2 gateway, and that it is online.
2. In Zerofy, add a Viessmann device.
3. Log in with your Viessmann account credentials and follow the prompts.
4. Enable Autopilot (Solar or Smart mode) for the Hot Water Tank.

Good to know: The Viessmann integration is in beta. Flow/circuit temperature can’t be set from Zerofy, and Autopilot currently steers only the hot-water tank; space-heating control is coming.

Step-by-step guide for Viessmann

3. Turn on Autopilot

In Zerofy, open your Viessmann heat pump, 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 Viessmann heat pump 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 Hoymiles solar production.

Learn more about Smart Mode

About Hoymiles and Viessmann

Hoymiles – Hoymiles (Hangzhou, China) is one of the largest microinverter makers. In Europe it is best known for balcony systems such as the HMS-800W-2T (switchable 600/800 W) with the MS-A2 balcony battery, and it also sells HYS/HYT hybrid inverters with home batteries. Monitoring app: S-Miles Cloud (S-Miles app).

Viessmann – Viessmann is a German heating manufacturer from Allendorf (Eder). Newer heat pumps such as the Vitocal 250-A and Vitodens boilers run on the Viessmann One Base platform with built-in Wi-Fi; older Vitotronic systems go online through a Vitoconnect gateway. Products: Vitocal 250-A, Vitocal 200-S, Vitodens 200-W/300-W boilers, Vitovalor fuel cells, older systems with Vitotronic controllers.

Manufacturer information last checked: October 2026.

All devices that work with Hoymiles