Heating the water is usually the largest part of a shower’s cost. A 10-minute shower at 9 L/min heated from 10 °C to 40 °C uses about 3.5 kWh of energy. Cutting shower time or fitting a low-flow head saves both water and energy.
How to use the Shower Cost Calculator
- People
- Showers per person per week
- Average shower length
- Flow rate
- Water and sewer price
- Energy price
- Temperature rise
- Water heater efficiency
Results update as you type, and every field accepts the units shown in its menu.
How it works
Enter the people in your household, showers per person per week and their length, the flow rate, the water and energy prices and the temperature rise and heater efficiency.
Tips
- Use the amounts printed on the product (ml, sheets, applications) where available.
- Count everyone in the household who shares the product.
- Buy a little extra so you never run out unexpectedly.
- Small daily habits add up – check the yearly figures for the real impact.
Common mistakes to avoid
- Forgetting that hot water costs energy as well as water.
- Underestimating how much sunscreen a full application needs.
- Comparing pack prices without checking the size of each pack.
Inputs explained
| Field | What to enter |
|---|---|
| People | A number |
| Showers per person per week | A number |
| Average shower length | In min |
| Flow rate | Units: gpm, L/min |
| Water and sewer price | Units: /1000 US gal, /m³ |
| Energy price | Units: /kWh, /therm |
| Temperature rise | In °C |
| Water heater efficiency | In % |
What each result means
- Water per shower = [Flow rate]×[Average shower length]×60
- Energy per shower = [Water per shower]×1000×4.186×[Temperature rise]÷3600÷([Water heater efficiency]÷100)
- Cost per shower = [Water per shower]×[Water and sewer price] + [Energy per shower]×[Energy price]
- Household cost per month = [Cost per shower]×[People]×[Showers per person per week]×52.18÷12
- Household cost per year = [Household cost per month]×12
- Water per year = [Water per shower]×[People]×[Showers per person per week]×52.18
Example values
How the main result changes when People changes and everything else stays at the example values above:
| People | Household cost per month |
|---|---|
| 1.5 | 25.68 |
| 2.25 | 38.52 |
| 3 | 51.35 |
| 3.75 | 64.19 |
| 4.5 | 77.03 |
| 6 | 102.71 |
Formula
Water per shower = flow rate × minutesHeating energy (kWh) = litres × 4.186 × temperature rise ÷ 3,600 ÷ heater efficiencyCost = water × water price + energy × energy priceWorked example
Inputs — People: 3; Showers per person per week: 7; Average shower length: 8 min; Flow rate: 2.1 gpm; Water and sewer price: $10 /1000 US gal; Energy price: $0.16 /kWh; Temperature rise: 30 °C; Water heater efficiency: 90 %.
Results — Water per shower = 16.8 US gal; Energy per shower = 2.46 kWh; Cost per shower = $0.56; Household cost per month = $51.35; Household cost per year = $616.25; Water per year = 18,409 US gal.
Frequently asked questions
How much does a shower cost?
Typically 30–80 cents including heating, depending on length, flow and energy prices.
How much water does a 10-minute shower use?
About 21 gallons (80 L) at 2.1 gpm, or 25 gallons with an older 2.5 gpm head.
How can I make showers cheaper?
Shorten them, fit a WaterSense low-flow head and lower the water heater temperature to about 50 °C (120 °F).
What formula does the Shower Cost Calculator use?
Water per shower = flow rate × minutes.