Bath vs Shower Water & Carbon Footprint Calculator
Enter how often you shower and take baths, your shower flow rate and bath volume, and see the annual water use and CO₂ emissions from heating that water — then find out which routine costs more in energy and emissions.
min
L/min
L
Water heater type
Showers + baths combined — based on 2024 energy carbon intensity estimates
- 1
Shower water per session
7 min × 8 L/min = 56 L - 2
Annual shower water
56 L × 7 × 52 = 20,384 L - 3
Annual bath water
150 L × 2 × 52 = 15,600 L - 4
Annual heating energy
35,984 L × 0.041 kWh/L = 1,475.3 kWh - 5
Annual CO₂
1,475.3 kWh × 0.2 kg/kWh = 295.1CO₂ factor: gas ≈ 0.20 kg/kWh, electric ≈ 0.21 kg/kWh (2024 estimates).
How does this calculator work?
Energy to heat water ≈ 0.041 kWh per litre (35 °C rise). Multiply by your annual volume — sessions × litres × 52 weeks — to get kWh, then by your heater's CO₂ factor (gas ≈ 0.20, electric ≈ 0.21 kg CO₂/kWh) for annual emissions. A 7-min standard shower uses ~56 L; a bath ~150 L.
Formula
How this is calculated
Heating water is one of the largest energy uses in a home. The energy required follows Q = m × c × ΔT, where m is mass (1 kg per litre of water), c is the specific heat capacity of water (4.186 kJ per kg per °C), and ΔT is the temperature rise — typically about 35 °C (from roughly 10 °C cold supply to 45 °C delivered hot water). That works out to about 0.041 kWh per litre of hot water, regardless of heater type.
Carbon dioxide emissions then depend on the fuel: a gas boiler running at ~90% efficiency emits roughly 0.20 kg CO₂ per kWh of heat delivered; UK electric resistance heating emits roughly 0.21 kg CO₂ per kWh (2024 UK grid average). These figures are approximate 2024 estimates and vary by country, season, and boiler age — treat them as editable baselines.
A standard shower using 8 L/min for 7 minutes consumes 56 litres, compared to a typical bath at 150 litres. But flow rate and duration matter enormously: a power shower at 12 L/min for 15 minutes (180 L) uses more than a full bath. The calculator multiplies per-session volumes by weekly frequency and 52 weeks to give annual totals you can act on.
Frequently asked questions
Not necessarily. A short 5-minute shower at 6 L/min uses only 30 litres — well below a 150 L bath. But a power shower at 12 L/min for 15 minutes uses 180 litres, more than most baths. Flow rate and duration are the key variables; use the calculator with your own figures.
A 150 L bath requires about 6 kWh of heating energy (at a 35 °C temperature rise). With a gas boiler that is roughly 1.2 kg CO₂, and with electric resistance heating roughly 1.3 kg CO₂ — per bath. Over a year of two baths per week, that is around 125 kg CO₂ from baths alone.
The biggest levers are: shortening shower time, fitting a low-flow shower head (6 vs 12 L/min halves water use), reducing bath frequency or filling the bath shallower, and switching to a heat pump water heater or solar thermal — which can cut the carbon factor per kWh by 50–80%.
TG we-Calculate Editorial Team. (2026). Bath vs Shower Water & Carbon Footprint Calculator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/bath-vs-shower-footprint-calculator
TG we-Calculate Editorial Team. "Bath vs Shower Water & Carbon Footprint Calculator." TG we-Calculate. 2026. https://we-calculate.com/calculator/bath-vs-shower-footprint-calculator.
TG we-Calculate Editorial Team, "Bath vs Shower Water & Carbon Footprint Calculator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/bath-vs-shower-footprint-calculator
@misc{wecalculate_bath_vs_shower_footprint_calculator, title = {Bath vs Shower Water & Carbon Footprint Calculator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/bath-vs-shower-footprint-calculator}}, year = {2026}, note = {TG we-Calculate} }
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