Steering the heat pump yourself

You absolutely can fine-tune a heat pump yourself — but with different levers than an old oil boiler. This chapter shows the safe controls that give you maximum control without damaging the machine.

The most important lever: the heating curve

The heating curve sets how the flow temperature responds to the outdoor temperature. It's your equivalent of "setting the temperature" — only smarter, because it scales automatically all year.

• Start low, then raise in small steps until it's comfortable on a cold day.
• Aim for the lowest curve that keeps you warm (every degree lower saves).
• Panel controllers offer this as a two-point setting (base/end point) or a graphical curve with a comfort factor.

The room setpoint (app)

Raising the room target temperature in the app, on a weather-compensated heat pump, shifts the whole heating curve up in parallel — it's not a thermostat measuring a room. More setpoint = higher flow = higher cost. A convenient fine lever, but with a price tag.

Operating modes

• Program / automatic: follows a schedule (comfort/ECO) — the recommended default.
• Constant comfort or ECO: holds one temperature (e.g. ECO while away).
• Standby / hot water (summer): heating off, only frost protection or only hot water.

A modest night setback (2–3 °C) is fine; deep setbacks are counterproductive, because the morning reheat costs more than the night saves.

The golden safety rule

Never choke the flow. The heat pump needs minimum flow while the compressor runs. So:

• Leave reference/leading rooms fully open — they secure the flow.
• Only trim individual overheated rooms with thermostatic valves.
• Don't close most valves or switch off circulation (that causes short-cycling and wear).

If you want less heat, lower the curve or the setpoint — not the flow.

And local (Home Assistant) control?

If your heat pump has an open interface (e.g. Stiebel ISG with Modbus), you can set exactly these safe levers — mode, setpoints — automatically from Home Assistant too: e.g. briefly raise the setpoint on solar surplus. The raw "maximum flow" setting is often protected, but via mode and setpoint you achieve practically the same.

In short: your safe levers are the heating curve, room setpoint and mode — never the flow. Leave reference rooms open, trim only overheated rooms, regulate less heat via the curve. With an open interface, all of this can be automated too.

On to the signal that brings PV surplus and the grid to the heat pump: SG-Ready in depth.