SL Energy + CTA

What Zerofy can do with SL Energy 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 SL Energy home system (3–12 kW) can cover on sunny days.
• Zerofy gets new SL Energy data every 5 minutes. Heat pumps shouldn’t switch often, so set a minimum runtime in Autopilot.
• Zerofy also shows your SL Energy 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 SL Energy and CTA offer on their own

SL Energy: SL Energy sells its own heat pumps (SL-HP9KL and SL-HP12/18KR, 12.6 to 23.8 kW, R32) in the iShare-Home package, and its SmartBox gathers data from inverter, meter, wallbox and heat pump. Whether the heat pump runs on solar surplus isn’t documented publicly.

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 SL Energy 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 SL Energy and CTA in Zerofy

1. Connect SL Energy

Zerofy connects to the SL Energy cloud: you log in with your SL Energy monitoring account (the one you use in the Smart M app).

1. Make sure your inverter is online and registered on the SL Energy monitoring platform.
2. In Zerofy, choose SL Energy and log in with your SL Energy account to grant access.

Good to know: For the battery, Zerofy supports forced charging but not switching the battery mode.

Step-by-step guide for SL Energy

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 SL Energy solar production.

Learn more about Smart Mode

About SL Energy and CTA

SL Energy – SL Energy (Slenergy Technology (Anhui) Co., Ltd., China) makes hybrid inverters such as the single-phase SL3.6-6KLV-W and SL3-10KLH-W and the three-phase SL5-12KRH-W, plus SL-BH high-voltage batteries. It also sells complete home packages (iShare-Home) with its own heat pumps and wallbox. Monitoring app: Smart M.

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 SL Energy