The choice of heating system is one of the most structuring in a renovation. It commits your home for 15 to 20 years and represents 20 to 35% of the energy renovation budget. In 2026, the two dominant options in Belgium are the air-water heat pump and the gas condensing boiler. Here is the numbers-based comparison to decide.
The 2026 context
Several parameters have changed since 2024:
- Progressive ban on heating oil: new oil-boiler replacement banned in Wallonia since 2026 (Brussels since 2025).
- Gas tariff: stable around €0.10 to €0.12/kWh LCV, moderate rise expected.
- Electricity tariff: €0.32 to €0.38/kWh residential, but off-peak tariff down to €0.18/kWh (Flanders, Wallonia).
- Boosted heat-pump grants: €4,500 in Wallonia, €4,000 in Brussels, €1,800 in Flanders.
Air-water heat pump: the system that takes the most space
How it works
An air-water heat pump captures calories from outside air and delivers them to your central heating circuit (radiators or underfloor heating). With 1 kWh of electricity consumed, it produces 3 to 4 kWh of heat (COP 3 to 4). This efficiency drops in extreme cold: at -10°C, the COP falls to 2 or 2.5.
Installation cost
| Item | 2026 range |
|---|---|
| 8 to 12 kW air-water heat pump | €6,000 to €9,000 |
| Installation and connections | €3,000 to €5,000 |
| Heating circuit adaptation | €0 to €4,000 |
| Total ex VAT | €9,000 to €18,000 |
| VAT 6% | + €540 to €1,080 |
| Total incl VAT | €9,540 to €19,080 |
2026 grants
- Wallonia: €4,500 (up to €6,000 for modest incomes)
- Brussels: €4,000 (Renolution)
- Flanders: €1,800 (Mijn VerbouwPremie)
Running cost
For a 100 m² home with 90 kWh/m².year heating need (PEB C):
- Heating consumption: 9,000 kWh/year thermal
- With average COP 3.2: 2,813 kWh electric
- Annual heating cost: €900 to €1,070 (depending on electricity tariff)
Pros
- Uses renewable energy (the air)
- No mandatory boiler maintenance (just an annual check)
- Also useful for cooling in summer (reversible heat pump)
- Compatible with photovoltaic for self-consumption
- Better environmental impact
Cons
- Performance degraded by extreme cold (back-up needed if T < -10°C)
- Outdoor unit noise (45 to 55 dB depending on model)
- High initial investment
- Poorly insulated home: very long ROI (the heat pump works better at low temperature)
Gas condensing boiler: the safe bet
How it works
The condensing boiler burns natural gas and recovers heat from the flue gases via a condensing exchanger. Efficiency of 95 to 105% on LCV (vs 70 to 80% for an old boiler).
Installation cost
| Item | 2026 range |
|---|---|
| 24 kW condensing boiler | €2,200 to €3,500 |
| Installation and connections | €1,500 to €3,000 |
| Flue (if replacement) | €600 to €1,500 |
| Total ex VAT | €4,300 to €8,000 |
| VAT 6% | + €258 to €480 |
| Total incl VAT | €4,558 to €8,480 |
2026 grants
- Wallonia: €200 to €800 depending on income
- Brussels: €750
- Flanders: no national grant (but local grants possible)
Running cost
For the same 100 m² home at 90 kWh/m².year:
- Heating consumption: 9,000 kWh/year thermal
- At 100% efficiency: 9,000 kWh gas
- Annual heating cost: €900 to €1,080
Pros
- Initial investment 2 to 3 times lower
- Constant performance year-round (not weather-dependent)
- Maintenance well mastered by all heating engineers
- Suits any housing type (poorly insulated included)
Cons
- Fossil gas: significant CO₂ impact
- Uncertain regulatory evolution (gas ban planned in the longer term)
- Mandatory annual maintenance (~€140 to €200)
- Not suitable for cooling
- No notable real-estate value added
The 15-year profitability calculation
On the same 100 m² home rated C:
| Air-water HP | Condensing boiler | |
|---|---|---|
| Initial investment incl VAT | €14,500 | €6,500 |
| Wallonia grant | -€4,500 | -€500 |
| Net cost | €10,000 | €6,000 |
| Annual heating cost | €1,000 | €980 |
| Annual maintenance | €80 | €180 |
| Total cost 15 years | €26,200 | €23,700 |
At equal home energy class, the condensing boiler remains more profitable over 15 years. But if you add:
- A photovoltaic installation (HP + PV = partial autonomy): the heat pump moves ahead
- A gas price evolution at +3%/year (vs +2% electricity): the heat pump moves ahead
- Cooling in summer (reversible HP): non-monetised added value
The decider: the home's insulation level
This is the key factor. The tipping threshold is the heating need in kWh/m².year:
- < 60 kWh/m².year (PEB B or better): heat pump = clear winner. Low temperature, good COP, no backup needed.
- 60 to 120 kWh/m².year (PEB C or D): both options are defensible, choice depends on environmental preferences and budget.
- > 120 kWh/m².year (PEB E, F, G): condensing boiler more pragmatic short term. But the ideal is to insulate FIRST, then install a heat pump on an insulated home.
The 3 questions to ask before choosing
1. Is my home well insulated?
If not, insulate first. Heat pump on a poorly insulated home = bad idea (massive electricity consumption in winter). See our article PEB Wallonia.
2. Do I have access to natural gas?
If you are on heating oil or propane and the street is not connected to gas, the connection cost (€3,000 to €8,000) kills the boiler's profitability. The heat pump becomes the logical option.
3. Am I owner for 10+ years?
If you plan to resell within 5 years, the condensing boiler pays back faster. For 15 years and more, the heat pump + insulation is the best path.
How to find the installer
For grants in Wallonia or Brussels, the installer must be RESCERT-certified (heat pump) or accredited heating engineer (boiler). In Flanders, EPB label for grants.
On Batizzy, you filter by certification, area and reviews. Find a heating engineer near you.
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