All the data Molleau publishes, gathered on one page: results measured by sensor, calculation assumptions and standard projections. Every figure is sourced and dated. This data is freely citable with attribution.
Sensor measurement in real conditions: 28 homes equipped, 28 analysed, in a Hénéo student residence (RIVP group) in the 13th arrondissement of Paris, from November 2025 to June 2026, across 3,140 showers, in two phases (silent baseline, then light ring active).
| Indicator | Value | Source and period |
|---|---|---|
| Average consumption per shower, before | 45 L | Phase 1 (silent sensor), Hénéo pilot. Full protocol |
| Average consumption per shower, after | 34.7 L | Phase 2 (light ring active), derived from the measured 23% reduction |
| Average reduction per shower | −23% | Phase 1 versus phase 2, same showers, same occupants, across 3,140 showers |
| Maximum individual reduction | up to −61% observed | Hénéo pilot: the higher the starting consumption, the larger the reduction |
| Carbon avoided | ≈ 0.25 tCO₂e | Over the year of the pilot, the equivalent of ≈ 1,400 km by car. 0.0321 kWh per litre of hot water (38 °C from 15 °C, network losses 1.2), heat network emission factor 0.183 kgCO₂/kWh, water and sewerage 0.35 kgCO₂/m³, ADEME Base Carbone 2025 |
| Reported change in awareness | 83% | One-month survey of equipped residents, November 2025 to July 2026 |
| Overall satisfaction | 5 / 5 | Median at the six-month resident review (mean 4.4 / 5); all 7 respondents recommend the device |
In the Hénéo pilot (RIVP group, Paris 13th arrondissement, 28 homes equipped, November 2025 to June 2026, 3,140 showers), switching on the Molleaumètre light ring cut hot water use by 23% per shower and by 15.5% on the building's main meter, with reductions of up to 61% observed among the heaviest users, with no change to flow or pressure. Source: Molleau, molleau.com/en/key-figures.html.
Every estimate Molleau publishes rests on these assumptions, all adjustable in the online calculator.
| Parameter | Value | Basis |
|---|---|---|
| Average domestic consumption in France | 150 L/day | Per person, all domestic uses (drinking, cooking, washing). 150 L in 2022, 146 L in 2023, from SISPEA reports by the French national observatory for water and sanitation services |
| Domestic water per hotel night | 150 L | Molleau assumption for the shower alone, per occupied room per day, 4-star hotel. Consistent with the 2024 French DGE study (240 to 323 L per night across all uses depending on the segment, of which 40 to 45% for cleaning) and with national domestic consumption (SISPEA) |
| Average volume of a shower | 45 L | Value measured during the baseline phase of the Hénéo pilot |
| Price of water (supply + sewerage) | €4.69/m³ | Approximate French national average, to be adjusted to the local tariff |
| Heating energy per litre | 0.030 kWh/L | Heating water from 15 °C to 41 °C (shower temperature) |
| Price of electricity | €0.1940/kWh | French regulated tariff, to be adjusted to the contract and heating source (gas, heat pump) |
| Emissions per kWh of electricity | ≈ 0.06 kg CO₂ | Average French electricity mix |
| Emissions from drinking water | ≈ 0.30 kg CO₂/m³ | Production, treatment and distribution of water |
Indicative estimates calculated with the rate measured in the Hénéo pilot: 23% less hot water per shower on average (up to 61% observed for the heaviest user). Same assumptions as the hotel page and the calculator.
| Hot water saved per year | 403 m³ |
| Savings per year (water + heating) | ≈ €5,658 * |
| Molleau subscription per year (€6 per month per room) | €2,880 |
| Net gain from year 2 | ≈ €2,780 |
| CO₂ avoided per year | ≈ 2.6 t |
| Water saved per year | ≈ 378 m³ |
| Savings per year (water + heating) | ≈ €4,100 * |
| CO₂ avoided per year | ≈ 2.4 t |
* Indicative estimates calculated with the assumptions in section 2, all adjustable in the calculator. Actual results depend on your property, your tariffs and your heating source.
These figures are published under a CC BY 4.0 licence, so you may reuse them freely with attribution. Suggested citation:
Molleau, “Key figures”, molleau.com/en/key-figures.html, accessed June 2026. Hénéo pilot (RIVP group), Paris, November 2025 to June 2026, 3,140 showers: 23% less hot water per shower, 15.5% less on the main meter, up to 61% observed less among the heaviest users.
Need the detailed protocol, the full report or an interview? Contact the team, we reply within 48 hours. The full pilot report is available on request.
The calculator applies these assumptions to your portfolio: hotel rooms or homes, occupancy rate and local tariffs.