Heat pump: is your home ready?

In short
A heat pump takes heat from the outside air (or from the ground) and brings it indoors. For 1 kWh of electricity it delivers about 3 kWh of heat in practice (2.8 to 3.4 measured; up to 4.5 on paper). It works best in a well-insulated home, with radiators or underfloor heating that give enough heat on lukewarm water. So insulate the roof first and check your radiators. Then ask for quotes and work out your grant. You can apply for Mijn VerbouwPremie (the Flemish renovation grant) for a heat pump until 31 December 2027, inclusive.

What you hear: what is true?

How does a heat pump work?

You heat with gas or heating oil (mazout) today. A heat pump replaces the boiler with a device that runs on electricity. That raises questions. How can a device take heat from cold air? Is my home suitable? What does it cost, and what do I get back?

Cold air also contains heat. Only at -273 °C is there no heat left at all. Air at -5 °C feels cold, but it still holds a lot of energy.

A heat pump works like a fridge running in reverse. A fridge takes heat from its inside and gives it off at the back, in the kitchen. A heat pump takes heat from outside and gives it off in your home.

This is how it goes:

1. The device contains a refrigerant. It is made colder than the outside air. Heat then flows from the air into the refrigerant.
2. A compressor squeezes the refrigerant. This uses electricity. The refrigerant gets hot, like a bicycle pump warms up when you pump hard.
3. The hot refrigerant gives its heat to the water in your central heating. Then the cycle starts again.

So the electricity is mostly used to move heat, not to make it. That is why the pump delivers more heat than the electricity it uses. For each kilowatt hour (kWh, the unit on your bill) you get about 3 kWh of heat. This figure is the seasonal efficiency. In field trials it lies between 2.8 (the median of the UK Electrification of Heat trial) and 3.4 (the average of 61 installations in Germany, Fraunhofer ISE). The weakest German installation reached 2.6. On paper the figures are higher: Test-Aankoop gives 4 to 4.5 with water at 35 °C. Such a figure is called the SCOP and is calculated from laboratory measurements. Measured in a real home, it is called the SPF. If you need water at 55 °C, as in a poorly insulated house, Test-Aankoop gives about 3 to 3.5. An electric heater delivers 1 kWh of heat per kWh of electricity.

The efficiency depends on two things. The colder it is outside, the harder the pump works. And the hotter the water has to be, the less the pump delivers. That is why the way heat is given off in your home matters so much (see below).

Is your home ready?

A heat pump heats at lower temperatures than a boiler. A gas boiler often heats the water to 60 °C or more. A heat pump works best with water at about 35 to 45 °C. Then it uses the least electricity.

So ask yourself two questions: does your home keep its heat, and do your radiators give enough heat on lukewarm water?

1. Does your home keep its heat?

If your home loses a lot of heat, the pump has to run for a long time and you pay a lot for electricity. Insulate first what leaks the most. In older homes that is usually the roof, because warm air rises. Windows, walls and floor come next.

The EPC (energy performance certificate) of your home and your heating bills from the last few years give a first picture.

2. Do your radiators give enough heat?

With underfloor heating this is seldom a problem. With radiators it depends on their size. Small, old radiators need hot water. Larger ones give enough heat even on lukewarm water.

Often it is enough to replace the radiators in the coldest rooms with larger ones. So your home does not need a full rebuild. The government tool Warmtepompklaar ("heat pump ready") gives a first indication. According to that site, "quite a few older homes with radiators" are already ready for a heat pump. The tool does not replace a calculation by an installer.

Mijn VerbouwPremie has a hard limit: the system may heat the water to 55 °C at most.

Which type of heat pump?

• Air-to-water. An outdoor unit takes heat from the air and heats the water in your central heating. This is the usual choice in a renovation.
• Geothermal. The heat comes from the ground or the groundwater. This needs a borehole or space in the garden, and a higher investment. The heat source is more stable, though.
• Hybrid. A small heat pump works together with a gas condensing boiler. This can be a halfway step if your home is not ready yet. You then keep your gas connection.
• Air-to-air. The device blows warm air into a single room. It does not heat radiators. It suits separate rooms or an extension.
• Heat pump water heater. This device heats only your domestic hot water.

A good installer looks at the heat loss of your home and chooses the output from that. A pump that is too small leaves you cold in a frost. A pump that is too large switches on and off all the time. That is neither economical nor quiet.

What changes in daily life?

The heat comes more evenly. A heat pump heats gently and for a long time at a stretch. You no longer get short, hot bursts of heating. After a cold night, though, the warm-up takes longer.

Frost. An air-to-water pump keeps working in frost, but its efficiency drops. The outdoor unit defrosts itself now and then. So put the unit in an open spot with free airflow, not right against a wall.

Noise. The outdoor unit makes noise. Think of your bedroom and your neighbours. Ask for the noise level and the position of the unit on the quote in advance.

Hot water. Domestic hot water needs a higher temperature than the heating. This is often done with a boiler or buffer tank that heats up now and then. That use comes on top of your electricity bill.

More electricity, no gas. Your electricity use goes up, especially in winter. Your gas or heating oil use goes away. Ask your installer to check that your electrical installation and connection can cope.

The capaciteitstarief (capacity tariff)

This tariff is part of your network costs, the amount that Fluvius (the network operator) charges. It depends on your highest quarter-hour peak: the quarter of an hour in the month when you use the most electricity at once. For the annual bill, the average of your monthly peaks over the last 12 months counts. Everyone pays at least the amount for a peak of 2.5 kW.

The tariff differs by network operator. The Flemish average in 2026 is about €53.39 per kW per year (excl. VAT), according to the Vlaamse Nutsregulator (VNR, the Flemish regulator). For Fluvius Limburg it is around €49 per kW per year, according to the Fluvius Limburg tariff list for 2026.

A worked example with €49 per kW. Say your average peak rises from 3.5 kW to 5.5 kW, because the heat pump and the cooker run at the same time. This part of your network costs then rises from about €172 to about €270 per year (excl. VAT). That is not a reason to give up on a heat pump. It is a reason to ask whether the pump, the charging point or the cooker really have to run at the same time.

Hydrogen as an alternative for heating?

You sometimes hear that green hydrogen could replace the heat pump. The numbers say otherwise. From 100 kWh of grid electricity, an air-to-water heat pump with a seasonal efficiency of 2.8 to 4.0 keeps about 270 to 380 kWh of heat. A hydrogen chain keeps only about 40 to 58 kWh of heat from the same 100 kWh, because of losses in electrolysis, compression, transport and in the boiler. So hydrogen needs about 4.6 to 9.5 times more electricity for the same heat, with a central value of just over 6.

The numbers for the chart are our own calculation, based on figures from the Clean Hydrogen Partnership and the European Hydrogen Backbone. The idea comes from a blog by David Cebon (University of Cambridge, 2020). That blog is not peer reviewed, covers the United Kingdom and uses an average winter demand of 70 GW. Cebon arrived at 5.5 to 6 times more electricity.

Hydrogen does have a place in processes that are hard to electrify, such as steel and cement (Fluxys). A hybrid system with a small heat pump remains a halfway step for homes that are not ready yet (see the grant table below). For homes, we found no Flemish or federal plan that uses hydrogen. According to VRT NWS of 16 September 2026, a Fluvius spokesperson says the natural gas network is not suitable for hydrogen, and the Flemish government had Fluvius prepare the phase-out of the gas network.

Heat pump or hydrogen for your home?

How much heat you get at home from 100 kWh of electricity, through a heat pump or through green hydrogen in a boiler.

• Heat pump
• Green hydrogen in a hydrogen boiler
• Lost
• Free heat from the surroundings

Per kWh of electricity, a heat pump gives 4.6 to 9.5 times as much heat as green hydrogen in a boiler. The central value is 6.4 times.

Drawn with the central values. The table also lists the values most and least favourable to hydrogen.

Sources

• World Bank, Electric power transmission and distribution losses (% of output) (opens in a new tab) (2025 ) primary source
• Energy Systems Catapult, Electrification of Heat Demonstration Project (opens in a new tab) (2023 ) primary source
• Clean Hydrogen Partnership, Strategic Research and Innovation Agenda: Key Performance Indicators (opens in a new tab) (2022 ) primary source
• US Department of Energy, Alternative Fuels Data Center, Fuel Properties (opens in a new tab) primary source
• Gas for Climate, European Hydrogen Backbone (opens in a new tab) (2020 ) company
• Eunomia for ECOS, Technical Feasibility of Hydrogen Boilers in Homes (opens in a new tab) advocacy group
• Fraunhofer ISE, Wärmepumpen heizen auch im Altbau klimafreundlich (opens in a new tab) (2025 ) academic
• David Cebon, Hydrogen for heating? A comparison with heat pumps, part 1 (Hydrogen Science Coalition) (opens in a new tab) (2022 ) advocacy group
• Test-Aankoop, Wat is het rendement van een lucht-waterwarmtepomp? (opens in a new tab) press
• Ulf Bossel, Does a Hydrogen Economy Make Sense? Proceedings of the IEEE (opens in a new tab) (2006 ) academic

Our own diagram, based on calculations by David Cebon (University of Cambridge), field measurements from Fraunhofer ISE and the other sources below.

Show the figures as a table

Heat at home from 100 kWh of electricity

Scenario	Heat pump efficiency (SCOP)	Heat via heat pump (kWh)	Heat via hydrogen (kWh)	Ratio
Favourable to hydrogen	2.8	267.4	58	4.6
Central	3.4	324.7	50.9	6.4
Unfavourable to hydrogen	4	382	40.2	9.5

Steps in the central scenario

Route	Step	Efficiency	Left over (kWh)
Heat pump	Power grid	95.5%	95.5
Heat pump	Heat pump	×3.4	324.7
Green hydrogen in a hydrogen boiler	Power grid	95.5%	95.5
Green hydrogen in a hydrogen boiler	Electrolysis	66.6%	63.6
Green hydrogen in a hydrogen boiler	Compressing hydrogen	92.5%	58.8
Green hydrogen in a hydrogen boiler	Moving hydrogen	92%	54.1
Green hydrogen in a hydrogen boiler	Hydrogen boiler	94%	50.9

Grant and money (as of 30 October 2026)

Mijn VerbouwPremie

Mijn VerbouwPremie is the Flemish grant for renovation work. It depends on your income category. There are four categories. Category 1 is the highest income category and category 4 the lowest. You can see which one you are in the simulator on vlaanderen.be or through the Energiehuis (the energy advice centre).

The grant was reformed on 1 March 2026. Owner-occupiers in categories 1 and 2 now get a grant only for a heat pump or a heat pump water heater. They no longer get a grant for insulation, windows or other work. Categories 3 and 4 do not change.

Conditions:

• You can apply for the grant until 31 December 2027, inclusive.
• The invoice is at least €1,000 excl. VAT.
• The heat pump is completely new. There is no grant for a second-hand device.
• A Rescert installer (certified for renewable energy installations) with the right certificate fits or validates the device.
• The heating water temperature is 55 °C at most.

Amounts for applications from 1 March 2026 (home, or private part of an apartment):

The grant is also capped at a share of the invoice (excl. VAT): 50% in category 4, 35% in category 3, 25% in category 2 and 20% in category 1. You get the lower of the table amount and that percentage.

An example. Say you have an air-to-water pump fitted for €14,000 excl. VAT.

• In category 3 the table gives €4,500. 35% of the invoice is €4,900. You get €4,500.
• In category 1 the table gives €1,500. 20% of the invoice is €2,800. You get €1,500.

So the same installation gets very different support. Know your income category before you sign.

In categories 3 and 4 the grant can rise by 50%. This applies if you replace electric heating or live in an area without natural gas. The maximum percentage still applies. The increase for electric heating needs an exclusive night tariff. If your home runs on heating oil, that does not mean automatically that you live in an area without natural gas. Check with the Energiehuis.

VAT

A heat pump in a home that is at least 10 years old usually falls under the 6% VAT rate for renovation. The VAT rules have changed in recent years, especially for younger homes and hybrid devices. Ask your installer to state the VAT rate and the conditions on the quote, and check them with FPS Finance (FOD Financiën).

Mijn VerbouwLening

With Mijn VerbouwLening (the Flemish renovation loan) you borrow €4,000 to €60,000 for renovation work, over up to 25 years. For owner-occupiers in categories 4, 3 and 2 the interest rate in 2026 is 0%, 0.5% and 1.5% respectively. The Energiehuis assesses your financial situation, so you may get less than the maximum.

Quote and preparation

Ask for at least two quotes and compare them for the same work. A low price is no bargain if the radiators, the electrical work or the removal of the old boiler are missing. A good quote states:

• the type and output of the heat pump, and the noise level;
• the efficiency (SCOP, a laboratory value) and the water temperature the installer is counting on;
• the heat loss calculation for your home;
• a boiler or buffer tank, if needed, and which radiators or zones will be changed;
• what happens to your old boiler and, with heating oil, to the tank;
• warranty, maintenance, after-care and the position of the outdoor unit.

Prepare for the first meeting. Write down your use for the last two or three years: gas in kWh or m³, heating oil in litres. Note which rooms stay cold. Take photos of the boiler room, the meter cupboard, the radiators and the spot for the outdoor unit.

Frequently asked questions

Can I leave my gas boiler in place? With a hybrid system, the pump and the boiler work together. With a full heat pump you usually drop the old boiler. It costs maintenance and takes up space.

Do I need solar panels? No. Panels do lower your electricity bill. But the pump uses the most electricity in winter, and then the panels deliver the least.

Can I switch over in one weekend? Seldom. Allow weeks to months for quotes, work on radiators and electrics, and the installation. So do not wait until your boiler gives out in the first cold week.

What now?

1. Write down your use and take the photos.
2. Take the Warmtepompklaar test.
3. Call or email Energiehuis Limburg (089 77 81 29). The advice is free. Ask about your income category and your grant.
4. Then ask Rescert installers for quotes.

Sources and disclaimer

Grants, conditions and loans come from Mijn VerbouwPremie for heat pumps, for heat pump water heaters, the changes from 2026 and Mijn VerbouwLening. The capaciteitstarief comes from the Vlaamse Nutsregulator. The readiness check comes from Warmtepompklaar.

The seasonal efficiency figures come from the Electrification of Heat trial (Energy Systems Catapult), Fraunhofer ISE and Test-Aankoop. The hydrogen calculation is our own, based on figures from the Clean Hydrogen Partnership, the European Hydrogen Backbone, the US Department of Energy, Eunomia for ECOS and the World Bank. The idea behind it comes from David Cebon (2020 blog, 2022 version), who took his efficiencies from Bossel (2006). The blog is not peer reviewed. The role of hydrogen in industry comes from Fluxys. The statements about the gas network come from VRT NWS and Solar & Storage Magazine.

Disclaimer: This is general information, not personal advice and not a quote. Grants, VAT and tariffs can change. Check them with the Energiehuis or in the simulator on vlaanderen.be before you decide. As of 30 October 2026.