Shower Cost Calculator

Calculate what a shower actually costs by combining the water you use with the electricity needed to heat it, based on your flow rate, duration, and temperature rise.

Quick Facts

Formula
Gallons × 8.34 lb/gal × ΔT ÷ 3,412 BTU/kWh
Converts the heat energy needed (BTU) into electric kWh, then divides by heater efficiency.
Assumption
95%-efficient electric resistance water heater
Gas and tankless heaters have different efficiencies and fuel pricing — see the FAQ.

Your Results

Calculated
Cost per shower
-
Water + water-heating energy
Water used per shower
-
Flow rate × duration
Energy used per shower
-
Electricity to heat the water
Estimated annual cost
-
Based on showers per week

Ready

Set your shower duration, flow rate, and utility prices, then press Calculate.

How the shower cost formula works

A shower has two separate costs: the water itself, and the energy used to heat it. This calculator adds them together using standard physics for heating water and your local utility prices.

Step by step

  • Water used (gallons) = showerhead flow rate (GPM) × shower duration (minutes).
  • Heat energy needed (BTU) = gallons × 8.34 lb/gallon (weight of water) × 1 BTU per lb per °F (specific heat of water) × temperature rise (°F).
  • Energy in kWh = BTU ÷ 3,412 (the number of BTU in one kWh), then divided by the water heater's efficiency to get the electricity actually drawn.
  • Energy cost = electricity (kWh) × your price per kWh. Water cost = gallons × (water & sewer price ÷ 1,000).
  • Cost per shower = energy cost + water cost. Annual cost = cost per shower × showers per week × 52.

Assumptions built into the result

The calculator assumes a standard electric resistance water heater running at 95% efficiency, water weighing 8.34 lb per gallon, and a constant flow rate for the whole shower. "Temperature rise" is the difference between the cold water entering the heater and the temperature at the showerhead — a common default is about 45°F, such as raising 60°F groundwater to a 105°F shower. Actual incoming water temperature varies by season and location, so adjust it if you know your numbers.

Typical reference values

U.S. WaterSense-certified showerheads are rated at 2.0 GPM or less, while older fixtures can use 2.5 GPM or more. An average shower commonly runs 7-10 minutes. Electricity and water/sewer rates vary widely by utility and region, so the defaults here are only a starting point — check a recent bill for your actual prices.

Frequently Asked Questions

What formula does this shower cost calculator use?
Water used = flow rate (GPM) × duration (minutes). Heat energy needed = gallons × 8.34 lb/gallon × 1 BTU/(lb·°F) × temperature rise, converted to kWh by dividing by 3,412 BTU/kWh, then divided by water-heater efficiency. Energy cost = kWh × electricity price. Water cost = gallons × (water & sewer price ÷ 1,000). Cost per shower is the sum of the two.
Does this work for gas or tankless water heaters?
The calculator assumes a 95%-efficient electric resistance water heater priced in dollars per kWh. Gas storage heaters run at roughly 60-70% efficiency and gas is billed per therm, so the same BTU math applies but the last two steps need a therm price instead of a kWh price. Tankless heaters skip standby losses entirely, so their real-world cost is usually a bit lower than this estimate.
How much does an average shower cost?
With the defaults on this page — an 8-minute shower, a 2.1 GPM showerhead, a 45°F temperature rise, $0.16/kWh electricity, and $9 per 1,000 gallons for water and sewer — a shower costs a little under 50 cents, or roughly $150-180 a year at seven showers a week. Your own numbers will differ with local rates and habits.
How can I lower the cost of a shower?
Because cost scales with gallons used (flow rate × duration) and with temperature rise, the two biggest levers are a shorter shower and a lower-flow showerhead — cutting either by a given percentage cuts water and heating cost by roughly that same percentage. A WaterSense-certified showerhead (around 1.5-2.0 GPM) uses less water per minute while using aeration to keep pressure feeling strong.

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