Shower & Hot Water Cost Calculator

What do your household showers cost, and what could lower flow, shorter showers or both save? Compare water and hot-water energy using your own utility rates.

Variable operating costs only. Utility prices are blank until you enter them; water and energy estimates still work without prices.

Current & Proposed Showers

Current shower

Use measured flow if available; labeled flow can differ.

Household

Positive whole number.

Decimals are allowed; zero represents no showers.

Proposed shower

Blank hides payback. Purchase price only; no labor, financing, maintenance or rebates.

Optional

Measure My Shower Flow

Don't know your actual GPM? Collect the shower water for a measured amount of time.

How to measure

The labeled flow rate may differ from actual flow because of water pressure, showerhead condition, installation or modification. Estimate it by collecting water for a measured time.

  1. Run the shower normally.
  2. Collect the full shower stream for a measured number of seconds.
  3. Measure the collected water.
  4. Enter the amount and collection time below.

Any measured collection time is fine. A larger container may be needed for high flow. This is a practical estimate, not laboratory-grade measurement.

Optional

Find My Water/Sewer Rate

Use your utility bill to estimate the variable rate affected by water savings.

Enter your combined usage rate in the main input above. No helper is needed.

How to read your bill

Look at your water bill for charges that change with the amount of water you use. These may be labeled usage, consumption, water volume, sewer usage or similar. Utility bills vary.

Do not include fixed monthly/base/service charges: those generally do not disappear when consumption falls. With tiered pricing, the marginal rate applying to gallons you expect to save is generally the most useful planning input. This helper does not model tier schedules.

CCF means hundred cubic feet. 1 CCF is approximately 748 US gallons; calculations use 748.052.

Hot Water & Utility Cost

Annual use always uses 365 days.

70% is an editable planning example.

Enter your incoming-water assumption.

Must be warmer than incoming water.

Use your variable water + sewer usage rate. Blank means unknown.

Choose the purchased-energy source.

Editable planning example; standby losses excluded.

Your variable electricity rate. No national-average rate is supplied.

About these assumptions

More than zero and up to 31; decimals allowed. Annual use always uses 365 days.

70% is an editable planning assumption, not universal. Incoming cold-water temperature, shower temperature, heater temperature and mixing behavior affect this share. Cold-water volume is not heated in this model.

Enter your assumption; no ZIP code or geographic estimate is used.

The difference between these temperatures sets the heating energy. Hot water must be warmer than incoming water.

Use the marginal/usage rate for additional consumption when possible. Blank means unknown; enter 0 only if the usage charge is actually zero.

Efficiencies below are editable planning assumptions for useful heat divided by purchased energy. They do not add tank standby or pipe losses. This is not a heat-pump/COP model.

100% is a resistance-electric planning example, not a claim that standby losses are included.

60% is an editable planning example, not a value for all gas water heaters.

Enter greater than 0% through 100%. Use the simple useful-heat conversion efficiency; do not enter a heat-pump COP or assume a UEF is interchangeable.

How it works

Flow rate × shower time gives gallons per shower. People and shower frequency give daily use; your selected month and 365 days give monthly and annual use. Your hot-water fraction estimates the share supplied by the heater.

Useful heat is hot-water gallons × 8.34 lb/US gallon × the heater-to-incoming temperature rise in °F, in BTU. Purchased heat is useful heat ÷ efficiency as a fraction. Electric energy in kWh is purchased BTU ÷ 3,412; gas energy in therms is purchased BTU ÷ 100,000. This uses approximately 1 BTU per pound of water per °F.

Water/sewer cost uses all shower gallons at your entered rate; heating cost uses purchased energy at your entered rate. Both rates are required for a total operating-cost estimate and payback. Missing rates are not treated as free. The comparison isolates flow and shower-time changes by keeping the other assumptions the same.

Understanding the estimate

70% hot water, 100% electric efficiency and 60% gas efficiency are editable planning examples. The hot-water share depends on incoming cold-water temperature, shower temperature, water-heater temperature and mixing behavior. The cold portion is not heated. This calculator does not derive the mixing share automatically or estimate temperatures from geography.

This is a variable operating-cost estimate. It excludes fixed water, sewer and gas service charges, water-heater standby losses, pipe heat losses, recirculation systems, tiered utility pricing, minimum charges, taxes, installation labor, maintenance and rebates. Use your applicable marginal/usage rates. Actual showerhead flow can vary with pressure, condition and installation; behavior may change. Hot-water fraction is an estimate unless measured.

Custom efficiency uses the same simple purchased-energy model with kWh or therms. It does not model heat-pump water heaters, COP or seasonal/tank UEF losses. A percentage reduction is unavailable if the current baseline is zero. More expensive proposed showers are reported as additional cost, not savings.