Growatt + CTA

What Zerofy can do with Growatt 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, which a typical Growatt home system (2.5–10 kW) can cover on sunny days.
• Zerofy gets new Growatt data every 5 minutes. Heat pumps shouldn’t switch often, so set a minimum runtime in Autopilot.
• Zerofy also shows your Growatt battery, so you can see whether surplus goes into the battery or into the heat pump.
• 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 Growatt and CTA offer on their own

Growatt: The GroBoost heater controller sends surplus solar to immersion heaters, adjustable from 0 to 10.8 kW across three outputs (three 3.6 kW single-phase heaters or one three-phase heater). Growatt’s own product pages don’t mention control of heat pumps or SG Ready.

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 Growatt 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 Growatt and CTA in Zerofy

1. Connect Growatt

Zerofy connects to the Growatt cloud: you log in with your ShinePhone credentials.

1. Make sure your inverter is online and registered in the ShinePhone app.
2. In Zerofy, choose Growatt and log in with your ShinePhone username and password.

Good to know: Inverter data is supported; battery and meter data may only be partly available depending on the system. Battery control and using the battery in Autopilot are listed as coming soon for Growatt.

Step-by-step guide for Growatt

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 Growatt solar production.

Learn more about Smart Mode

About Growatt and CTA

Growatt – Growatt (Shenzhen Growatt New Energy, China, founded 2011) makes string and hybrid inverters such as the MIN TL-X and MIN TL-XH series, the NEO microinverters and the NOAH 2000 balcony battery. Its own ecosystem, GroHome, adds the THOR wallboxes, APX HV batteries and the GroBoost heater controller. Monitoring app: ShinePhone.

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 Growatt