Not all heat pumps are equal. Performance, costs, and installation constraints vary considerably depending on the technology. And the wrong choice is paid for over 20 or 25 years — in comfort, in running costs, and in headaches. This comparison covers the three main families available in Suisse romande with the honesty the subject demands: none is universally the best, and the right choice depends on the context.
The three main families of heat pumps
Air-to-water heat pump: extracts heat from outdoor air via a unit installed outside the home (or in a plant room with ducting), and transfers it to a water circuit feeding radiators or underfloor heating.
Ground-to-water heat pump (vertical geothermal): extracts heat from the subsoil via vertical probes descending 100–250 metres into the ground. The captured heat is transferred to an indoor water circuit.
Water-to-water heat pump (groundwater): extracts heat from an underground aquifer via two wells (one pumping, one return). Very efficient, but subject to rare cantonal permits.
A fourth category exists: the air-to-air heat pump (reversible air conditioning). It treats air directly, without a water circuit, and resembles a warm air conditioner more than a central heating system. It is covered in a separate article because it is not in the same league for primary heating in a temperate climate.
The air-to-water heat pump: the de facto standard
Of the installations we carry out in Suisse romande, more than 80 % are air-to-water. For straightforward reasons.
Controlled installation cost. A residential air-to-water heat pump is installed in two to four days. No boreholes, no complex permit, no intervention on the subsoil or the site. Allow CHF 35,000 to CHF 48,000 gross installed for a 150–180 m² detached house.
Sufficient performance. Air-to-water heat pumps of 2025–2026 (Daikin Altherma 3 H HT, Mitsubishi Ecodan, Hitachi Yutaki, Viessmann Vitocal 250-A) achieve SCOPs of 3.8 to 4.3 in the Vaud lowlands, on well-sized installations with low-temperature radiators or underfloor heating. That is sufficient for comfort equivalent to oil heating, with primary energy consumption three to four times lower.
Near-universal applicability. An air-to-water heat pump can be installed in virtually any home, from a mountain chalet to a 1980s villa, with one caveat for buildings in protected zones where the outdoor unit may raise aesthetic objections.
The disadvantages exist and should be known:
- Noise from the outdoor unit (40–50 dB at 3 metres). Poor positioning leads to lasting neighbour conflicts.
- Performance drops at very low temperatures. At -15 °C, the COP falls to around 2.5–3, versus 4 at +7 °C. This is a physical reality, and it is factored into the SCOP.
- The aesthetics of the outdoor unit are not to everyone's taste, especially in tourist areas or listed buildings.
For 80 % of replacement projects in Suisse romande in 2026, the air-to-water heat pump remains the optimal choice for performance, cost, and complexity.
The geothermal heat pump: superior performance, at a price
Vertical geothermal is technically superior. It draws heat from the subsoil at a constant 12–15 °C year-round, versus an average of 3–8 °C for ambient air in winter. This difference translates directly into SCOP.
Performance. SCOP of 4.5 to 5.2 on well-designed installations. That is 20 to 30 % better than an equivalent air-to-water system over its full service life.
Stability. Because ground heat is constant, a geothermal heat pump delivers stable output in mid-winter, whereas an air-to-water system loses 30–40 % of efficiency. This is the decisive argument at altitude (above 1,000 m) where winter temperatures are more demanding.
Discretion. No visible outdoor unit. All equipment is in the plant room. No perceptible noise from outside.
The downside: cost and constraints.
Cost. Including boreholes, allow CHF 55,000 to CHF 80,000 gross installed in 2026 — CHF 20,000 to CHF 35,000 more than an equivalent air-to-water system.
Land. Accessible ground is required for boring equipment, with sufficient passage for the machine. On confined plots, in densely built areas, or on protected sites, this is not always feasible.
Permits. In Suisse romande, geothermal boreholes require cantonal authorisation. This permit can take three to six months, sometimes more, and depends on groundwater protection maps. Certain zones are simply excluded. Feasibility must be verified before committing to a project.
Lead times. Allow six to nine months from decision to full commissioning, versus two to three months for an air-to-water system.
Our advice: geothermal is justified for new builds (where probes are integrated during groundworks), for homes with high thermal needs (>200 m² poorly insulated), or at altitude. For a standard lowland renovation, the additional cost is recouped over 12–15 years — acceptable but not exceptional.
The water-to-water heat pump: maximum performance, but…
The groundwater heat pump is in theory the most efficient: SCOP of 5 to 6 on well-designed installations, because groundwater sits at 10–12 °C year-round and provides a near-ideal heat source.
In practice, in Suisse romande in 2026, it has become a niche reserved for very specific cases. Cantonal permits on aquifers are rare, conditioned on zero impact on water quality and a full hydrogeological study. Most cantons have tightened conditions since 2018.
When permitted, the installation cost exceeds that of vertical geothermal (two wells + permit + studies), for a marginal SCOP gain over a good geothermal system. For new high-end villa projects immediately adjacent to a favourable aquifer, it may make sense. For typical residential use, it is not a realistic option.
Summary comparison table
| Criterion | Air-to-water | Geothermal | Water-to-water |
|---|---|---|---|
| Seasonal SCOP | 3.5 – 4.3 | 4.5 – 5.2 | 5.0 – 6.0 |
| Gross installed cost (150 m²) | CHF 35,000 – 48,000 | CHF 55,000 – 80,000 | CHF 70,000 – 100,000 |
| Total installation lead time | 2 – 3 months | 6 – 9 months | 9 – 12 months |
| Cantonal authorisation | Simple notification | Borehole permit required | Hydrogeological study |
| External noise | 40 – 50 dB | None | None |
| Cold-weather sensitivity | Moderate | Low | Low |
| System service life | 20 – 25 years | 25 – 35 years (probes 50 years) | 25 – 35 years |
| Annual maintenance | CHF 250 – 400 | CHF 200 – 350 | CHF 300 – 450 |
Which choice for which profile
Individual home 100–200 m², lowland, standard renovation, contained budget: air-to-water, without hesitation. It is the solution sized for this profile and it works very well.
New build, land available, intention to keep the home 20+ years: seriously consider geothermal. Integration during construction reduces the relative additional cost, and the long-term performance pays over time.
Home at altitude (>1,000 m), critical winter comfort: geothermal wins on performance. Air-to-water can also work, but with more generous sizing and attention to frost protection.
Listed building, protected zone, strong aesthetic constraints: geothermal if a permit can be obtained, otherwise air-to-water with a well-concealed unit. Some brands offer very discreet split modules.
High-end villa, confirmed groundwater feasibility, high budget: water-to-water, to be verified with a prior hydrogeological study.
PPE under renovation, multiple units, large surface area: collective air-to-water or shared geothermal depending on the site. Both work in multi-unit buildings and benefit from economies of scale.
The criterion most often overlooked
The installer. A poorly installed geothermal heat pump performs worse than a well-installed air-to-water unit. That is where the whole difference lies. The choice of technology only has value if it is accompanied by correct sizing, careful configuration, and follow-up during the first years to adjust the heating curves.
A high-end heat pump installed by a multi-brand reseller who provides no follow-up can prove disappointing. A mid-range heat pump installed by a team that returns twice in the first year to optimise settings will deliver better results in practice.
Before choosing between air-to-water and geothermal, choose the installer. Then listen to their recommendation for your particular case. And if it does not match your initial intuition, ask to understand why. The right reasons always exist.