The monobloc that does away with an outdoor unit. The exchanger and fans sit in a single indoor cabinet (utility room, cellar); air enters and exits through two discreet grilles cut into the façade. The ideal answer when an outdoor unit is banned — apartment block, listed façade, no garden or balcony.
The figures that matter for a heat pump without an outdoor unit, installed by our teams. Concrete benchmarks, not marketing.
The entire unit — compressor, exchanger, fans — fits in a single cabinet placed indoors (utility room, cellar, larder). Nothing on the roof, balcony or façade: no outdoor footprint, no bracket to fix.
Outdoor air is drawn in then expelled through two ducts connected to two discreet grilles cut into the façade (about 16 cm in diameter). The only visible element outside: two vents that can be matched to the render or stonework.
The seasonal efficiency is slightly behind a conventional split: the airflow passes through ducts, which limits the output. Expect 3.5 to 4.2 kWh of heat per electrical kWh depending on the model and the home’s insulation.
The fan is indoors: we install the cabinet in a technical room, away from bedrooms. On the façade side, no unit runs — so zero nuisance for neighbours, the deciding factor in terraced housing.
Depending on the model, the heat pump feeds underfloor heating or low-temperature radiators, and produces domestic hot water via an integrated or remote tank. A single machine for the comfort of the whole home.
The cabinet takes up the footprint of a large fridge, with clearance to allow in front of the ducts. We fit it in a utility room or a dry cellar; a room of about 2 to 3 m² is plenty.
* Indicative values for standard indoor monoblocs. Exact performance depends on the model, the duct length and the home’s insulation — confirmed during the survey.
No solution is perfect for every home. Here, honestly, is where the indoor monobloc excels and where you’d be better off looking elsewhere.
It comes into its own as soon as an outdoor unit is banned, impossible or unwanted. A few cases where it shines:
When the building’s rules or the AGM ban any unit on the façade or balcony, the indoor monobloc fits without altering the building’s shared appearance.
In a protected area or on a listed building, mounting an outdoor unit is out of the question. Two grilles matched to the facing respect the heritage.
A terraced house, with no yard or patio, or with very close neighbours sensitive to noise: everything stays indoors, without bothering anyone.
If you can place a unit outside, an air-to-air heat pump heats quickly at lower cost, and an air-to-water heat pump feeds radiators and underfloor heating with better efficiency.
On a town house in a protected area, mounting an outdoor unit was impossible. We installed an indoor monobloc in the cellar, linked to two grilles matched to the blue stone. The old oil boiler is gone, the façade stayed intact and the heating bill melted away.
5.0/5 · 3verified reviews
« Châssis, panneaux et pompe à chaleur en une seule fois : on a eu un seul devis, un seul planning et zéro paperasse pour les primes. Le résultat est impeccable et notre facture d'énergie a chuté. On ne pensait pas que ce serait aussi simple. »
« Passage du mazout à une pompe à chaleur air-eau. Chantier propre, anciens radiateurs conservés. La maison est mieux chauffée pour bien moins cher. »
« PAC air-air réversible installée avant l'été. Confort été comme hiver, et le SAV répond vite. Très satisfait du suivi. »
The monobloc wins when no outdoor unit is possible. Compare it point by point with air-to-air and air-to-water, then open the solution that interests you.
| Critère | Heat pump, no outdoor unitVous êtes ici | Air-to-airVoir la gamme → | Air-to-waterVoir la gamme → |
|---|---|---|---|
| Outdoor unit | None | Unit required | Unit required |
| Façade impact | 2 discreet grilles | Visible unit | Visible unit |
| Noise for neighbours | None outside | Outdoor fan | Outdoor fan |
| Efficiency (SCOP) | Good: 3.5–4.2 | Very good: 4–5 | Very good: 3.8–4.8 |
| Domestic hot water | Possible (tank) | No | Yes, integrated |
| Radiators / underfloor | Depending on model | Blown air | Yes, full network |
| Ideal for | Apartment block, façade, no outdoor space | Heat quickly, small budget | Replacing a boiler |
The best efficiency to heat quickly, on a small budget, and cool in summer. Requires an outdoor unit.
Compare with air-to-air →Feeds radiators, underfloor heating and domestic hot water. The natural replacement for a boiler.
Discover air-to-water →Air-to-air, air-to-water, monobloc, geothermal: the full overview to spot the technology made for your home.
See all types →For domestic hot water alone, the thermodynamic tank cuts the hot water bill by three.
See the water heater →Regional grants, reduced VAT and 2026 conditions: what the State covers on your heat pump.
See the grants →An overview of our heat pumps in Belgium: technologies, installation, efficiency and grants on one page.
Back to the heat pump guide →The price depends on the power output, the uses (heating only or with hot water) and the length of the ducts to the façade. Here are some benchmarks for an installed indoor monobloc.
See the detailed heat pump price list →* Indicative ranges for an installed indoor monobloc, excluding specific configurations. A costed estimate is provided with your free quote.
The entire refrigerant circuit sits in a single cabinet placed indoors. Instead of an exchanger mounted outside, the unit draws in outdoor air and expels it through two ducts connected to two grilles cut into the façade (about 16 cm in diameter). The warmth in the air is captured indoors, with no visible unit outside.
Slightly. Routing the air through ducts reduces the flow, so the SCOP sits around 3.5 to 4.2 versus 4 to 5 for a split with an outdoor unit. The gap stays moderate and the solution still cuts the bill compared with oil or gas, especially in a well-insulated home.
It’s actually its natural home. Since nothing is mounted on the façade or balcony, you don’t need an AGM approval to alter the building’s shared appearance. The two grilles stay discreet and can be matched to the facing.
No noise on the façade side: there’s no outdoor fan running. The only sound comes from the indoor cabinet, around 35 to 42 dB(A), which we install in a utility room or cellar away from bedrooms. It’s the deciding factor in terraced housing.
Yes, depending on the model. Some monoblocs include a thermodynamic tank or control a remote tank to handle both heating and domestic hot water with a single machine. We size the whole setup to the number of occupants during the survey.
It’s recognised as a heat pump: it therefore qualifies, depending on your region and income, for the heat pump grant (up to around €4,000) and reduced 6% VAT for homes over ten years old. We put together the grants file for you.
Free site survey, grants calculated, a single point of contact. Describe your project in under a minute.