Shower vs Bath Cost Calculator
Compare the water and water-heating cost of a shower against a full bath, and see which is cheaper for your habits.
How it works
Shower gallons = flow × minutes · Heat kWh = gallons × 8.34 × °F ÷ 3412 ÷ 0.98 · Cost = gallons × water + kWh × rate
A shower and a bath cost the same way — water down the drain plus the energy to heat it — so the winner comes down to volume. Heating water is the larger cost: it takes about 8.34 BTU to raise one gallon by one degree, and there are 3412 BTU in a kilowatt-hour. A short shower with a modern head uses less water than filling a tub, but a long shower with a high-flow head can easily exceed a bath, which is why time and flow rate decide it.
Worked example
At 2.1 gpm for 8 minutes a shower uses 16.8 gallons. Heating that by 50°F takes 16.8 × 8.34 × 50 ÷ 3412 ÷ 0.98 ≈ 2.1 kWh. Water is 16.8 × $0.015 = $0.25 and heat is 2.1 × $0.17 = $0.36, so $0.61. A 35-gallon bath costs about $1.27 — the shower saves roughly $0.66.
Frequently asked questions
When does a shower cost more than a bath?
Long showers or a high-flow head flip the result. At 2.5 gpm a 15-minute shower uses 37.5 gallons — more than a typical bath. Cutting a few minutes or fitting a low-flow head keeps showers the cheaper choice.
How do I estimate the temperature rise?
It is the hot-water target minus the incoming cold-water temperature. Groundwater is often 50–60°F and showers run around 100–105°F, so a 45–55°F rise is typical; use a higher number in winter when incoming water is colder.
Does gas water heating change the answer?
The water cost is unchanged; only the heating cost differs. Gas is usually cheaper per unit of heat than electricity, so gas-heated homes see a smaller energy gap between shower and bath, but the volume comparison still drives the result.
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This calculator is for educational purposes. Double-check important results before acting on them.