Shower Cost Calculator
What your showers cost in water and in the energy to heat it — per shower and per year — and what a shorter shower or a low-flow head would save.
A shower uses flow rate × minutes of water; heating it from cold to shower temperature takes 4.
How the shower cost calculator works
A shower uses flow rate × minutes of water; heating it from cold to shower temperature takes 4.186 kJ per liter per degree, divided by the water heater’s efficiency. Water is priced per 1,000 liters; heating is priced per kilowatt-hour of electricity, or gas converted to the same unit. Heating is usually two-thirds or more of the total, which is why a shorter shower saves more than a cheaper water tariff.
Formula: litres = flow × minutes; heating kWh = hot litres × 4.186 × ΔT ÷ 3,600 ÷ efficiency
Worked examples
| Inputs | Cost per year | Note |
|---|---|---|
| 8 minutes at 9 L/min, 14 a week | 725.96 | about 0.99 a shower, 720 a year |
| Old 15 L/min head, 10 minutes | 780.67 | gas heating at 0.09/kWh |
| Four-minute showers with a heat pump | 113.53 | a fraction of the cost |
FAQFrequently asked questions
How much water does a shower use?
Old shower heads run 15–20 liters a minute; water-efficient ones 6–9. An eight-minute shower is therefore anywhere from 50 to 160 liters — the flow rate matters more than the minutes.
Why is heating the bigger cost?
Raizing 70 liters by 25 °C takes about 2 kWh — 0.50–0.65 at typical electricity prices — while the same 70 liters of water costs a few cents. A heat pump or solar hot water changes that ratio.
What temperature rize should I use?
Shower water is about 38–40 °C; mains water is 8–15 °C in a temperate winter and 20–25 °C in a hot summer, so 15–30 °C covers most situations. Use the annual average for a yearly figure.
How do I price gas per kWh?
One kWh is 3.6 MJ, so divide your price per megajoule by 0.278 (or divide the price per therm by 29.3). Then enter about 80% efficiency for a storage gas heater, 85% for instantaneous.
Where these figures come from
- International Energy Agency — Energy Efficiency — appliance consumption and standby power context
- US Energy Information Administration — the federal energy statistics agency
Last checked: September 2026. Appliance power figures are typical ratings; check the label on your own equipment, which is authoritative for it.