Why a heat pump doesn't behave like your oil boiler

Years with an oil boiler leave you with a set of habits: set a fixed flow temperature, throttle the radiator valves, switch the circulation off in mild weather. That works for the boiler — and with a heat pump it's almost entirely the opposite of what makes it efficient and long-lived.

This piece explains the two decisive differences, and how they end up giving you more control, not less.

An oil boiler doesn't care how you run it

An oil burner delivers hot water on demand — whether 50 °C or 70 °C flow, whether many or few radiators are open, whether you switch it hard on and off. Its efficiency barely changes. That's why you can steer it as bluntly as you like.

A heat pump is a different machine with two hard constraints.

1. A heat pump wants to run long and gently — not hot and intermittent

Its efficiency (the seasonal performance factor) is highest when it modulates at the lowest flow temperature that keeps your house warm. Every degree of flow you remove is real money: going from 50 °C to 45 °C flow means roughly 8–12 % less electricity.

So the biggest lever you control isn't "set a fixed 50 °C" — it's run the flow as cool as the house tolerates, via the heating curve.

2. It must never be "dead-headed"

This is the one that can actually damage the machine. A heat pump needs a minimum water flow through it whenever the compressor runs, to carry the heat away.

The oil-boiler habit of closing most thermostatic valves and throttling circulation is risky here: if too many radiators are shut, the pump has nowhere to push its heat. It then short-cycles (rapid on/off), and over time that wears the compressor.

This is exactly why the offers include a buffer tank — it gives the pump somewhere to dump surplus heat.

The good news: "off when mild, on when cold" is built in

What you currently do by hand — throttle in mild weather, heat more when it's cold — is exactly what the weather-compensated heating curve does automatically, and better. An outdoor sensor measures the temperature, and the curve continuously scales the flow: near-off when mild, ramping up in the cold, without you touching anything.

You're hand-simulating a heating curve. The heat pump does it natively — and more smoothly, because slow modulation always beats hard cycling.

What you can safely control yourself

From "do this freely" to "leave this alone":

Freely — your main levers:

Tune the heating curve. This is your equivalent of "set 50 °C," only smarter: you decide how the flow responds to outdoor temperature. Start low and nudge up until it's comfortable on a cold day.
Adjust the room target temperature in the app (a parallel shift of the curve) — fine anytime.
Switch modes — scheduled (program) vs. constant comfort/ECO, or summer standby.
A modest night setback (2–3 °C) is fine. Deep setbacks are counterproductive — the morning reheat costs more than the night saves.

With care — your thermostatic valves:

You can keep them, but the rule changes: leave the leading/reference rooms' radiators fully open (they guarantee the minimum flow) and use valves only to trim back individual overheated rooms — never to shut down large parts of the system.

Avoid — the oil-boiler reflexes:

Don't close most valves / kill the circulation to "save." That risks short-cycling and wear. If you want less heat, lower the curve or the room target instead.
Don't run a fixed high flow (50 °C) as the default. Let the curve pull it down in mild weather.
Don't hard on/off the whole system daily.

The mental shift

With the oil boiler you think in on/off and throttling. With the heat pump you think in set the right curve once, then let it modulate — and your fine control runs through temperature targets (curve, room setpoint, valve trim on non-reference rooms), never through cutting the flow.

You end up with more effective control, not less: the curve gives you a precise, whole-season response you set yourself, and the app lets you shift it anytime. You give up only the one habit that would harm the machine.