Heat pump: simple checks to keep your running costs down

A heat pump does not create heat by burning fuel. It moves heat from the outside air, the ground or groundwater into your home. According to the Flemish government, it takes 60 to 80% of the energy it needs from its surroundings and only the rest from electricity (Vlaanderen.be). How much the remaining electricity costs you depends a lot on how the system is used. Below are checks you can do yourself, wherever you live in Belgium, without opening or adjusting anything on the installation.

Steady and low works best

The Flemish energy regulator gives a simple rule: to use a heat pump efficiently, heat at a low temperature and keep the temperature you want constant (Vlaamse Nutsregulator). The same page advises you to go over the best settings for your own heat pump together with your installer.

In practice, that means:

• Pick one comfortable setting on the room thermostat and leave it. Turning it up and down several times a day works against the "keep it constant" advice.
• Be careful with big night-time drops. A habit learned with an old gas or oil boiler, such as turning the heating far down every evening, may not suit your heat pump. Ask your installer what night setting fits your home and your type of heating.

Flow temperature in plain words

The flow temperature is the temperature of the water the heat pump sends to your floor heating or radiators. The lower it can stay while the house remains comfortable, the better. Brussels Environment puts it this way: the smaller the gap between the temperature of the source (the air, water or ground the heat comes from) and that of your radiators or floor, the more efficiently the heat pump works (Bruxelles Environnement). That is why low-temperature heating, such as floor heating or suitable radiators, suits it best.

Some systems have an outdoor sensor: a small thermometer outside that lets the system adjust the water temperature automatically to the weather (Woningpas Vlaanderen). You do not need to change this yourself. If rooms are too warm in mild weather, or never quite warm enough, write it down and ask your installer to look at it.

Hot water: comfort, but safely

Hot water is not the place to cut corners. The Flemish Department of Care advises keeping hot water at at least 55 °C, ideally 60 °C, because the legionella bacterium, which can grow in hot water, dies above 55 °C (Departement Zorg). After a holiday, it advises running all taps for a few minutes.

If your system has a programme that regularly heats the water tank to a higher temperature (often called an anti-legionella function), ask your installer how it is set and when it runs.

Check this yourself

1. Thermostat: note the setting you use now, day and night, for one week.

2. Your own data: with a digital (communicating) meter, your network operator, named on your bill, shows your electricity use online:

   • Flanders: Mijn Fluvius shows it per day, month and year, and even per quarter-hour.
   • Wallonia: myORES shows your readings from the previous day and up to five years of history; a quarter-hour view can be switched on. With RESA, the MyRESA portal shows your use day by day and quarter-hour by quarter-hour.
   • Brussels: Sibelga offers the free My Sibelga app and a web portal.

   Remember that this is your whole home, not the heat pump alone.

3. The unit's display or app: if it shows energy use, note it once a month so you can compare months.

4. Peaks: see whether the heat pump runs at the same time as the oven, dryer or car charger. In Flanders, our article on the capacity tariff explains why that matters.

5. Look, don't touch: walk past the outdoor unit now and then. Leaves, snow or ice piling up around it, or an unusual noise, are worth mentioning to your installer.

Before you change anything

Write down what you noticed and ask your installer, rather than changing technical settings yourself. Brussels Environment advises having a heat pump checked regularly: filters need cleaning, and some parts wear. The Walloon energy administration stresses that a heat pump must be correctly sized and installed, and strongly recommends certified professionals (Energie Wallonie). Work on the refrigerant (the fluid inside the heat pump that carries the heat) is reserved by law: in Europe only recognised refrigeration technicians at recognised companies may handle it (Vlaanderen.be).

We cannot promise any saving: every home, installation and habit is different.

Want an independent look at your heat pump, meter data and bills? Tell us about your home.