Hoymiles + CTA

What Zerofy can do with Hoymiles and CTA

In practice

• When there’s enough surplus, Zerofy switches the relay and the heat pump receives the SG Ready signal. How it reacts – for example by heating the hot-water tank to a higher temperature – is set in the heat pump’s own controller.
• 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.
• CTA’s own tip for SG Ready operation: if rooms get too warm or too cold, change the upper temperature limit by 1 °C at a time and leave it for one to two days before adjusting again; agree the values with your heating installer.

What Hoymiles and CTA 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.

CTA: For PV self-consumption, CTA connects its heat pumps to external energy management systems via a PV input, SG Ready or Modbus (Optiheat and Aeroheat). CTA publishes SG Ready instructions per model and a compatibility list for the Swiss Solar Manager gateway (Modbus TCP/RTU).

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

Setting up Hoymiles and CTA 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 CTA

The Zerofy docs have no CTA-specific guide; the documented way to control a CTA heat pump is Zerofy’s SG Ready integration, with a smart relay such as a Shelly wired to the heat pump’s SG Ready inputs.

1. Check in CTA’s SG Ready compatibility list that your model and controller (Optiplus, Optiplus 3, Aeroplus 2.0/2.1) are listed.
2. Have an electrician wire a smart relay (e.g. Shelly) to the heat pump’s SG Ready inputs.
3. Add the relay to Zerofy and configure it as SG Ready controller.

Good to know: CTA marks Optiheat Inverta units and several Aeroheat models as needing a software or controller update for SG Ready. For older or unlisted units, CTA says integration can mean extra cost, e.g. a controller replacement.

Step-by-step guide for CTA

3. Turn on Autopilot

In Zerofy, open your CTA 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 CTA 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 CTA

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).

CTA – CTA AG is a Swiss manufacturer of heat pumps and cooling machines, with production at its headquarters in Münsingen near Bern. Its home range covers Optiheat ground-source and water-source heat pumps and Aeroheat air-source heat pumps. Products: Optiheat (brine/water and water/water), Optiheat Inverta, Aeroheat (air/water, indoor and outdoor units), Aeroheat Inverta.

Manufacturer information last checked: October 2026.

All devices that work with Hoymiles