In a home, domestic hot water costs you twice over: the price of the water, and the energy that heats it. The shower is the largest single use. Acting on it lightens both tenants' recoverable charges and the landlord's energy bill, a concrete lever against fuel poverty.
* Indicative estimate using the assumptions in the Molleau calculator: water and sewerage at €4.69/m³ (SISPEA 2025), heating at around 0.030 kWh/L, electricity at €0.1940/kWh (French regulated tariff, June 2026). Detail on the key figures page.
Why hot water counts twice in service charges
Every litre of hot water used in the shower costs two things: water and sewerage (roughly €4.69/m³ on average in France, SISPEA 2025 report) and heating energy (around 0.030 kWh to heat a litre from 15 °C to 41 °C). Depending on how hot water is produced, that energy falls either on recoverable charges (communal boiler) or directly on the tenant's own bill (individual cylinder).
The result: shower consumption is a significant cost, yet almost invisible, diluted between the water bill and the energy bill. Nobody sees it, so nobody optimises it.
Acting on the shower, the largest use
The shower is the largest single use of hot water in a home. It is also the most sensitive to behaviour: with no feedback, a tenant has no idea whether their shower uses 30 or 80 litres. Giving them that information while they are showering is enough to bring consumption down, with nothing imposed.
In the Hénéo pilot (RIVP group), switching on the Molleaumètre light ring cut consumption by 23% per shower, and by 15.5% on the residence main meter, with reductions of up to 61% among the heaviest users, without touching flow or pressure.
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What this means across 100 homes
Applied to a 100-home residence, a 25% reduction in shower water represents in the order of €4,300 to €6,900 in savings a year *, combining the cost of water, sewerage and heating energy. Those savings are split between tenants' recoverable charges and the landlord's energy bill. The calculator recalculates the figure using your own portfolio's parameters.
A concrete argument in the conversation with tenants
Reducing water charges is not only a saving: it is a matter of transparency and dialogue. Lower charges that can be explained, readable consumption data, an approach that builds responsibility without assigning blame: all concrete material to put to tenants and their representatives. It is also a lever against fuel poverty, particularly valuable in social and intermediate housing.
Domestic hot water weighs on two bills: the water and the energy that heats it. Cutting shower use by 23% on average (sensor measurement, Hénéo pilot, RIVP group, 2025-2026) lightens tenants' recoverable charges and the landlord's bill alike, in the order of €4,300 to €6,900 a year for 100 homes, with no building work and nothing imposed. Estimate your own portfolio with the Molleau calculator.
Sources: SISPEA report (French national observatory for water and sanitation services, 2025 price data); French decree no. 87-713 setting out the list of recoverable charges; Molleau x Hénéo pilot, RIVP group (2025-2026). Savings: indicative estimate, Molleau calculator.