A 50-room hotel at 80% occupancy uses at least 3,500 m³ of water a year, based on the 240 litres per person per night measured by the French Directorate General for Enterprise (DGE, 2024) for 1 to 3 star hotels, and more as soon as a room hosts two people. The shower is the first item: about 150 litres of hot water per occupied room per day, 2,190 m³ a year, which cost both the water and the heating energy. Here is the calculation item by item, and what it becomes with a shower water meter.
Molleau assumptions for hotels: 150 L of shower water per occupied room per day, 80% occupancy, water and wastewater €4.37/m³, heating from 12 to 40 °C at €0.298/kWh, i.e. €9.67/m³ of hot water, measured reduction of 23%.
How many nights and showers for 50 rooms?
A 50-room hotel at 80% occupancy sells 14,600 room-nights a year (50 × 365 × 0.8). If each occupied room means one shower a day, that is also 14,600 showers; with two occupants, twice as many. All the hotel's water consumption flows from that figure, and it is the one to adjust to your property: a business hotel at 65% occupancy on weekdays with couples at weekends has a different profile from a leisure hotel full in summer.
What is the total annual water consumption?
The DGE measures 240 litres of water per person per night in 1 to 3 star hotels, and 323 litres in 4 and 5 star, all uses combined: rooms, kitchen, laundry, cleaning, grounds and any pool. Applied to 14,600 nights with one person per room, that gives 3,504 m³ a year for a 1 to 3 star hotel, and 4,716 m³ for a 4 or 5 star. With 1.5 people per room on average, those volumes rise to 5,256 and 7,074 m³. At the average price of €4.37/m³ including water and wastewater, the water bill alone of a 50-room 3-star hotel therefore sits between €15,300 and €23,000 a year.
| 50-room hotel, 80% occupancy | 1 person per room | 1.5 people per room |
|---|---|---|
| Room-nights per year | 14,600 | 14,600 |
| Total water, 1 to 3 stars (240 L/person/night) | 3,504 m³ | 5,256 m³ |
| Total water, 4 and 5 stars (323 L/person/night) | 4,716 m³ | 7,074 m³ |
| 3-star water bill at €4.37/m³ | ≈ €15,300 | ≈ €23,000 |
Source for volumes per night: French Directorate General for Enterprise (DGE), study on water management in tourism, 2024 (240 L per person per night in 1 to 3 star hotels, 323 L in 4 and 5 star). Room-nights are computed from 50 rooms and 80% occupancy; replace with your own figures.
What share goes to showers?
The shower is the first water item in the room and the only one heated almost entirely. Molleau uses 150 litres of shower water per occupied room per day for hotels, which allows for longer showers than at home: on holiday, guests use 55% more water (Teragir, 2024). For 14,600 occupied rooms, that is 2,190 m³ of hot water a year. That water costs twice: €4.37/m³ for water and wastewater, and €9.67/m³ to heat it from 12 to 40 °C at €0.298/kWh, i.e. €14.04/m³ in total and close to €30,750 a year for the hotel.
How much does hot shower water cost per room?
Per occupied room, hot shower water costs about €2.11 per night (150 L × €14.04/m³). Over a year and 292 occupied nights per room, that is €615 per room, and €30,750 for 50 rooms. It is this item, more than the cold water bill, that determines the savings potential: every litre of shower water avoided also saves 0.032 kWh of heating.
How much can a 50-room hotel save?
With a shower water meter that displays litres in real time, consumption per shower falls by 23% on average, a result measured on 3,140 showers in the Molleau × Hénéo pilot, and up to 61% among the heaviest users. For a 50-room hotel, that is 504 m³ less hot water a year, about €7,070 in savings (water and heating), 16,300 kWh of heating avoided and 3.4 tonnes less CO₂. That figure counts shower water only: the challenges offered in the app (towels, air conditioning, housekeeping) come on top. The University of Surrey study (2024) confirms the mechanism in hotels, with showers 25.8% shorter when guests see their consumption.
| For 50 rooms, per year | Without a shower meter | With a shower meter (−23%) |
|---|---|---|
| Hot shower water | 2,190 m³ | 1,686 m³ |
| Water + heating cost of showers | ≈ €30,750 | ≈ €23,680 |
| Saving | ≈ €7,070, 504 m³, 3.4 t CO₂ | |
| Molleaumètre subscription (≈ €6 excl. VAT/month/device) | ≈ €3,600 |
Molleau assumptions for hotels: 150 L of shower water per occupied room per day, 80% occupancy, water and wastewater €4.37/m³, heating from 12 to 40 °C at €0.298/kWh, i.e. €9.67/m³ of hot water, measured reduction of 23%. CO₂: 0.195 kg per kWh (average electricity mix) and 0.35 kg per m³ of water. The subscription excludes the set-up fee. Details are on the Hotels page.
How do you bring these figures back to your hotel?
Three inputs are enough: your number of rooms, your occupancy rate and your water price, readable on the bill. The calculator applies the assumptions above and lets you change them one by one, including how water is heated and the set temperature. For actual consumption per room, the only reliable method remains measurement: our article How much water does a hotel room use per night? details the orders of magnitude and the observed gaps.
What would it mean for your rooms?
30 minutes to estimate your property's savings potential. No commitment.
A 50-room hotel at 80% occupancy uses at least 3,500 m³ of water a year (240 L per person per night, DGE 2024), including 2,190 m³ of hot shower water costing close to €30,750 in water and heating. A shower water meter at −23% saves about 504 m³, €7,070 and 3.4 t of CO₂ a year, before additional challenges. Source: Molleau, molleau.com, from the DGE and the Molleau × Hénéo pilot.
Frequently asked questions
How much water does a hotel room use per night?
240 litres per person per night in 1 to 3 star hotels, 323 litres in 4 and 5 star, all uses combined (DGE, 2024). For the shower alone, Molleau uses 150 litres of hot water per occupied room per day.
What is the water bill of a 50-room hotel?
Between €15,300 and €23,000 a year for a 3-star hotel at 80% occupancy, depending on whether you count one or 1.5 people per room, at the average price of €4.37/m³. The energy to heat shower water comes on top: about €21,000 a year at €0.298/kWh.
How much does a 50-room hotel save with a shower meter?
About 504 m³ of hot water, €7,070 and 3.4 tonnes of CO₂ a year, with the 23% reduction measured in the Molleau × Hénéo pilot. The app's challenges on towels and air conditioning add to that minimum.
How do I calculate my hotel's water consumption?
Multiply your rooms by 365 and by your occupancy rate to get room-nights, then by 240 or 323 litres and by the average number of occupants. The Molleau calculator does this and quantifies the possible savings with your water price.
Sources: French Directorate General for Enterprise (DGE), study on water management in tourism, 2024 (240 L per person per night in 1 to 3 star hotels, 323 L in 4 and 5 star); Teragir, water sobriety in tourism study, 2024 (+55% water on holiday); Eaufrance, "Average overall price of water at 1 January 2025" (SISPEA, French Biodiversity Office, 2024 report published 25 June 2026); University of Surrey, Journal of Travel Research, 2024 (showers 25.8% shorter with real-time feedback, in hotels). Reduction results: Molleau × Hénéo pilot, RIVP group, Relais d'Italie residence, 3,140 showers, November 2025 to June 2026 (full protocol). Specific heat of water 4.186 kJ per litre per degree.