SMA + CTA

What Zerofy can do with SMA 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 SMA home system (3–10 kW) can cover on sunny days.
• Zerofy gets new SMA data every 5 minutes. Heat pumps shouldn’t switch often, so set a minimum runtime in Autopilot.
• Zerofy also shows your SMA 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 SMA and CTA offer on their own

SMA: The Sunny Home Manager 2.0 runs heat pumps via EEBus (Vaillant, Wolf, NIBE S-series), SEMP (Stiebel Eltron, Tecalor, AEG) or an SG Ready input switched by a Shelly, Moxa or SMA relay. my-PV heating rods (AC ELWA, AC•Thor) are controlled via SEMP.

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 SMA 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 SMA and CTA in Zerofy

1. Connect SMA

Zerofy connects to your SMA system through the SMA Sunny Portal cloud, using your Sunny Portal login.

1. Make sure your SMA inverter is cloud-capable and registered in Sunny Portal.
2. Add SMA in Zerofy and log in with your Sunny Portal credentials.

Step-by-step guide for SMA

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 SMA solar production.

Learn more about Smart Mode

About SMA and CTA

SMA – German inverter maker based in Niestetal near Kassel. Homes typically have a Sunny Boy (single-phase) or Sunny Tripower (three-phase) string inverter, or a Sunny Boy Smart Energy (3.6–6 kW) or Sunny Tripower Smart Energy hybrid inverter with the SMA Home Storage battery (3.28 kWh modules, up to 16.4 kWh). Monitoring app: SMA Sunny Portal / SMA Energy 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 SMA