Shower Energy Cost Calculator

by

Estimate the water and water-heating cost of one shower and your household's monthly and yearly total.

Advanced options
Estimated household shower cost per monthThis combines water and heating costs for 30 days.
Water and heating cost per showerThis is the estimated cost of one shower at the entered length and flow.
Estimated household shower cost per yearThis uses the same shower pattern for 365 days.
Household shower water used per monthThis is the water sent through the showerhead during 30 days.
Electricity used for shower heating per monthThis is bought electricity after the efficiency adjustment.
Did we solve your problem today?

How to use our Shower Energy Cost Calculator

  1. Choose your Water heater fuel, then enter your shower's usual Shower length, Shower flow, and Household showers per day.
  2. Enter the matching Energy price from your electric or natural gas bill.
  3. Open Advanced options to add your Water and sewer price, temperatures, and Water heater efficiency if you know them.
  4. Click Calculate. Check that the monthly water use and the cost per shower seem reasonable for your shower length, flow, and household shower count.
Example inputs for Shower Energy Cost Calculator
Example inputs for Shower Energy Cost Calculator

Definitions

Shower flow: The amount of mixed water coming from the showerhead each minute, measured in gallons per minute.

Energy price: Your utility's charge per kWh for electricity or per therm for natural gas.

Water and sewer price: The combined local charge for 1,000 gallons of water and sewer service.

Cold water entering heater: The temperature of water before the water heater warms it.

Shower water temperature: The mixed water temperature delivered at the shower, not the heater thermostat setting.

Water heater efficiency: The percentage of purchased energy that becomes heat in the shower water.

kWh: Kilowatt-hour, a unit used on electric bills.

Therm: A natural gas billing unit equal to 100,000 Btu.

Btu: British thermal unit, a unit of heat energy.

Water used by shower lengthAt a 2.0 gallons per minute showerhead flow rate. Multiply these amounts by household showers per day for daily use.Water used by shower lengthAt a 2.0 gallons per minute showerhead flow rate5 minutes10 gallons10 minutes20 gallons15 minutes30 gallons20 minutes40 gallonsShower length
Water used by shower length
Multiply these amounts by household showers per day for daily use.

Common mistakes and quick fixes

Mistake: Entering the natural gas price while Water heater fuel is set to electricity.
Fix: Choose the correct fuel first. The Energy price is per kWh for electricity and per therm for natural gas.

Mistake: Using the showerhead's maximum rating instead of its actual Shower flow .
Fix: Use the listed gallons-per-minute rating or measure the flow if you want a closer estimate.

Mistake: Entering one person's showers in Household showers per day when several people use the same heater.
Fix: Add all daily showers that use that water-heating setup.

Mistake: Typing a monthly bill total into Energy price or Water and sewer price .
Fix: Enter the unit rate: $ per kWh or therm for energy, and $ per 1,000 gallons for water and sewer.

Mistake: Setting Shower water temperature at or below Cold water entering heater .
Fix: Enter a shower temperature higher than the incoming cold-water temperature.

Mistake: Leaving an unrealistic Water heater efficiency after changing fuel.
Fix: Review the efficiency setting. The untouched suggestions are 100 percent for electricity and 60 percent for natural gas.

Limitations & Key Assumptions / Boundary Conditions

  • The estimate treats all water from the showerhead as water heated from the entered incoming temperature to the entered shower temperature.
  • It does not include heat lost from pipes, a storage tank, recirculation lines, or water used while waiting for the shower to warm up.
  • Actual utility bills can include fixed charges, tiered rates, taxes, delivery charges, and separate sewer rules that are not captured by a single unit price.
  • Monthly cost uses 30 days and yearly cost uses 365 days, so a specific calendar month can differ.
  • Electricity is calculated with the entered efficiency. The calculator does not model heat-pump water heaters with a coefficient of performance greater than 1.
  • The result covers showers using the selected water-heating setup only. Baths, sinks, laundry, and other hot-water use are excluded.

Methodology

Calculation method

Water used by one shower is shower length times shower flow. The heat calculation uses the temperature rise from incoming cold water to mixed shower water.

water per shower (gallons) = Shower length (minutes) x Shower flow (gallons per minute)

heat needed (Btu) = water per shower x 8.34 x (Shower water temperature - Cold water entering heater)

For electricity, the calculator divides the needed heat by 3,412.142 Btu per kWh and by the efficiency fraction. For natural gas, it divides by 100,000 Btu per therm and by the efficiency fraction.

electricity per shower (kWh) = heat needed / (3412.142 x Water heater efficiency / 100)

natural gas per shower (therms) = heat needed / (100000 x Water heater efficiency / 100)

The water charge and fuel charge are added for one shower. That amount is multiplied by Household showers per day and 30 for the monthly estimate, or by 365 for the yearly estimate.

cost per shower = water per shower x Water and sewer price / 1000 + energy used per shower x Energy price

monthly household cost = cost per shower x Household showers per day x 30

yearly household cost = cost per shower x Household showers per day x 365

Mini-example

A 10-minute shower at 2 gallons per minute uses 20 gallons. With 55 F incoming water and 105 F shower water, the calculation adds 8,340 Btu of heat. At 100 percent electric efficiency and $0.16 per kWh, heating costs about $0.391 per shower. At $5 per 1,000 gallons, water and sewer add $0.10, for about $0.491 per shower.

Sources

  1. Showerheads | US EPA
  2. Shower Better | US EPA