A hotel guest in Europe uses between 150 and 250 litres of water per day. Around 30 to 40% of that is hot domestic water — that’s about 60 to 100 litres that need heating. In practice, this means a hotel with 100 guests consumes over 6,000 litres of hot water per day — the same applies to an apartment building with 40 flats. In industry, the figures quickly exceed 10,000 litres, especially in the food, chemical or textile sectors.
Heating 1,000 litres of water from 10°C to 55°C requires around 58 kWh of thermal energy. If provided by an electric boiler or inefficient boiler, this can cost around 10 euros per day — and nearly 4,000 euros a year for just one cubic metre of daily consumption.