Enphase + CTA

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

Enphase: The IQ Energy Router+ (IQ Energy Router plus Energy Meter and SG Ready Relay) controls one SG Ready heat pump. It only uses SG Ready states 2 (normal) and 3 (recommended on), and Enphase publishes wiring guides for Daikin Altherma 3, Vaillant aroTherm plus and iDM.

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 Enphase 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 Enphase and CTA in Zerofy

1. Connect Enphase

Zerofy connects to your system through the Enphase cloud: you log in with your Enphase Enlighten credentials and Zerofy reads PV production, meter (consumption) and battery data.

1. Make sure your system is online and you have an account on Enphase Enlighten.
2. In Zerofy, add an inverter, choose Enphase and log in with your Enlighten credentials.
3. Configure the meters: the grid meter as main meter (bi-directional or consumption), production as a sub meter of type production.

Step-by-step guide for Enphase

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 Enphase solar production.

Learn more about Smart Mode

About Enphase and CTA

Enphase – Enphase Energy (Fremont, California) makes microinverters: each panel gets its own IQ8 unit of about 300–330 VA, connected through an IQ Gateway. The AC-coupled IQ Battery 5P adds storage in 5 kWh steps, and everything is monitored in the Enphase App (Enlighten). Monitoring app: Enphase App / Enlighten.

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 Enphase