The key facts

  • 719 participants aged 18–65 lowered their shower water temperature for 12 weeks
  • Participants took on average 31% fewer sick days than the control group
  • Lowering the temperature from 40°C to 15°C in a 40-liter shower saves 1.3 kWh of energy; emissions fell by 15 kg of CO2 per person over 12 weeks

An experiment with 719 participants

An eco-friendly lifestyle is usually associated with giving things up — the car, flights, meat — or with expenses such as solar panels and an electric car. Psychologist Dr. Lena Glaser tested the opposite approach: small changes that bring personal benefits and fit easily into everyday life. In her words, 'when people see a personal benefit from changing their behavior and don't feel they are giving something up, they are more motivated to stick with those changes.' As an example, she chose cold showers: 'Taking a cold shower isn't very pleasant, but it's a small change,' and its impact is comparable to recycling waste.

How the study was conducted

The experiment involved 719 people aged 18 to 65. Selection criteria: good health and no prior habit of cold showering. Over 12 weeks, participants made the water as cold as their shower allowed. Some dropped out in the first two weeks, but the dropout rate then declined — Glaser believes that 'people gradually get used to it.' She notes that participants' environmental views were not recorded in advance, which limits the interpretation of the results.

What the results showed

Participants reported feeling energized right after the shower, and those who continued the experiment noted long-term improvements in physical and mental health. An objective indicator: on average, they took 31% fewer sick days than the control group. At the same time, euronews emphasizes that there are still few rigorous studies on the benefits of cold-water immersion — most of the claimed benefits (improved mood, energy, concentration, stronger immunity) are described at the level of anecdotal accounts.

Savings and emissions

People are less inclined to linger in a cold shower, so less water is used and heating requires less energy — which shows up in utility bills and emissions. For a 40-liter shower lasting three to four minutes, lowering the water temperature from 40°C to 15°C saves 1.3 kWh — roughly enough for one washing machine cycle or 100 phone charges. Over 12 weeks, participants reduced CO2 emissions by 15 kilograms per person — equivalent to a 100-kilometer car trip. Glaser notes that even small changes in water temperature have a positive effect, and advises starting gradually while paying attention to how you feel.