To reduce a hotel's energy bill, start with the two biggest items: heating and domestic hot water. Hot water is often overlooked because its cost is split across two bills, water and energy. Yet in hotel showers, over two thirds of the cost is the energy used to heat the water. When guests see their consumption during the shower, they use less hot water with the same flow: both bills go down at once.
* Molleau assumptions: 150 L of shower water per occupied room per day, heated from 12 to 40 °C (about 0.0326 kWh per litre), electricity at €0.298/kWh, water and sewerage at €4.37/m³ (French prices). Full detail in How much does hot water cost per hotel room?
Where a hotel's energy goes
In the hotel sector, heating and domestic hot water are the top energy costs, ahead of air conditioning and lighting (French Baisse les Watts programme, cited by Opéra Énergie). Each item has its own levers, and not all of them require building work.
| Item | Quick lever | Timeframe |
|---|---|---|
| Heating and air conditioning | Schedule unoccupied rooms, set temperature limits, cut air conditioning when windows are open | A few weeks |
| Domestic hot water: showers | Show guests their consumption during the shower, without touching the flow | Less than a day to install |
| Lighting | LEDs and presence detectors in corridors and back-of-house areas | A few weeks |
| Energy contract | Compare offers and renegotiate before renewal | At renewal |
Shower hot water: the cost nobody sees
Heating one litre of water from 12 to 40 °C takes about 0.0326 kWh. With 150 litres of shower water per occupied room per day, that is about 4.9 kWh per room night, for showers alone.
For a hotel with 40 rooms at 80% occupancy, or 11,680 room nights a year, shower water accounts for about 57,000 kWh a year. At €0.298/kWh, that is nearly €17,000 of energy, plus about €7,600 of water and sewerage. In total, close to €24,600 a year, 69% of it energy.
This item has one particularity: the hotelier does not control it. Shower length depends on the guest, who sees neither the litres nor the energy used. Heating can be scheduled and lighting automated. Showers still have no feedback at all.
And in your hotel?
Thirty minutes to estimate your water and energy savings. No commitment.
Inform guests rather than cut the flow
The classic answer is to cut the flow with aerators or low-flow shower heads. It works, though it changes perceived comfort, a sensitive point in hospitality, and some guests then shower longer. We compare both approaches in An alternative to low-flow shower heads in hotels.
The other approach is to make consumption visible during the shower. Guests keep the same flow and pressure; they simply see the litres go by. This is what the Hénéo pilot measured: from 45 to 34.7 litres per shower on average, or 23% less hot water, and therefore 23% less heating energy for this item.
France's tertiary decree: what it asks of hotels
In France, the tertiary decree (decree no. 2019-771 of 23 July 2019) applies to commercial buildings of 1,000 m² or more, hotels included. It sets cuts in final energy use of 40% by 2030, 50% by 2040 and 60% by 2050, against a reference year no earlier than 2010. Consumption is reported every year on ADEME's OPERAT platform.
Domestic hot water is part of the building's energy use. Any drop in shower hot water use therefore contributes directly to the target, with no building work and no room taken out of service.
What the Molleaumètre does
The Molleaumètre is a connected water meter that screws onto the shower hose. It displays the litres in real time, with a light ring that turns from green to amber to red. Flow and pressure stay the same. The Molleau team handles installation with no building work: a 40-room hotel is equipped in less than a day.
With 23% less per shower, a hotel saves about €141 per room per year, of which €97 is energy and €44 water, or nearly 330 kWh avoided per room. The dashboard tracks every room in litres, euros and CO₂, which also provides concrete figures for energy reporting and labels. The savings calculator redoes the maths with your own rates.
In hotel showers, 69% of the cost is heating energy, about 4.9 kWh per room night. Displaying consumption during the shower cuts hot water by 23% per shower (3,140 showers measured, Hénéo pilot), with no building work and no loss of comfort. Source: Molleau, molleau.com.
Frequently asked questions
What is a hotel's biggest energy cost?
Heating and domestic hot water are a hotel's top energy costs, ahead of air conditioning and lighting. Hot water is often underestimated because its cost is split between the water bill and the energy bill.
How much energy do hotel showers use?
With 150 litres of shower water per occupied room per day, heated from 12 to 40 °C, it takes about 4.9 kWh per room night. For a 40-room hotel at 80% occupancy, that is about 57,000 kWh a year, or nearly €17,000 of energy at €0.298/kWh.
How can a hotel cut its energy bill with no building work?
Levers that need no building work include scheduling heating and air conditioning in unoccupied rooms, renegotiating the energy contract and displaying consumption during the shower, which cuts hot water by 23% per shower on average, measured across 3,140 showers.
Does France's tertiary decree apply to my hotel?
Yes, if the hotel has 1,000 m² or more of commercial floor space in France. Decree no. 2019-771 sets cuts in final energy use of 40% by 2030, 50% by 2040 and 60% by 2050 against a reference year, with annual reporting on ADEME's OPERAT platform.
Sources: Baisse les Watts programme, cited by Opéra Énergie, “Energy savings in hospitality”; French decree no. 2019-771 of 23 July 2019 (Éco Énergie Tertiaire scheme); Molleau x Hénéo pilot, RIVP group, 3,140 showers analysed over eight months, from 45 to 34.7 L per shower on average. Molleau calculation assumptions: 150 L of shower water per occupied room per day, 80% occupancy, heating from 12 to 40 °C, electricity €0.298/kWh, water and sewerage €4.37/m³.