How Much Does a Bath Cost?

A typical bath costs about $1.20 with an electric water heater and about 70 cents with a gas water heater. That estimate assumes a 40-gallon fill at a comfortable 104 °F, and it adds up two charges: the water and sewer bill for the gallons, and the energy needed to heat them. Using example rates of $10 per 1,000 gallons, $0.17 per kWh and $1.50 per therm, a bath lands anywhere from about 60 cents to $2.50 depending on tub size and fuel. Your own number will shift with your local rates, so this guide shows the full breakdown, the formula to plug in your figures, and how a bath compares with a shower.

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Bath cost at a glance

Here is where the money goes in one 40-gallon bath. Every figure is an estimate built from the example rates in the caption, so swap in the rates on your own bills for a closer answer.

With an electric heater, heating is about two-thirds of the bill. With a gas heater, the water and sewer charge becomes the larger share, because gas delivers each unit of heat for less money. That split is the first thing to check when you wonder why a bath costs what it does.

Water and energy rates vary a lot between cities and utilities. Treat these figures as a model, not a quote.

Bath cost by tub fill

Most people don't fill a tub to the overflow. A standard tub holds roughly 40 to 80 gallons at the overflow drain, depending on the model, and a person's body displaces several gallons on getting in, so a comfortable depth often takes less water than the tub's rated capacity. This table shows what different fills cost under the same example rates and temperatures:

The pattern is linear: every extra 10 gallons adds about 30 cents with an electric heater and about 18 cents with a gas heater. A deep soaking tub costs roughly four times as much to fill as a shallow bath for a child.

What you're actually paying for

Water and sewer. Utilities usually bill water by volume, either per 1,000 gallons or per ccf (100 cubic feet, about 748 gallons). Sewer is often billed on the same volume, so a gallon that goes down the drain is effectively charged twice, once coming in and once going out. Some utilities base the sewer charge on winter water use instead, which can make summer baths cheaper than they look.

Heating energy. Raising the temperature of water takes a fixed amount of energy: about 1 Btu per pound per degree Fahrenheit. Since a gallon of water weighs about 8.34 pounds, each gallon needs roughly 8.34 Btu for every degree you raise it. Your water heater supplies that energy from electricity or gas, and the efficiency of the heater determines how much of it you pay for.

How to work out your own bath cost

Start with the energy needed to heat the water. It depends on how many gallons you run and how far the water has to be warmed:

Then convert the energy to your fuel's billing unit and multiply by your rate:

Here is the 40-gallon example worked through, with 55 °F incoming water and a 104 °F bath:

The bath cost calculator does these steps for you and lets you enter your own rates and temperatures.

What changes the cost the most

Your water heater

The same 40 gallons costs very different amounts to heat depending on the equipment. A heat pump water heater moves heat rather than generating it, so it delivers several units of heat per unit of electricity.

Real-world heat pump performance varies with the room and climate it sits in. The 3× figure is a round planning number, not a rating.

The season

Incoming water in winter can be far colder than in summer, so the heater has more work to do for the same bath. The effect is large:

The bath temperature

Heating cost scales with the temperature rise, so a hotter bath costs more. Going from 104 °F to 109 °F adds about 10% to the heating portion in the typical case above. It is a small saving per bath, but it compounds over a year of regular use.

Bath vs. shower: which costs more?

A shower uses water for as long as you stand under it, so its cost depends on flow rate and time. EPA notes that standard showerheads use 2.5 gallons per minute and that WaterSense labeled models use no more than 2.0. Here is how an 8-minute shower compares with a bath under the same assumptions:

A standard bath costs about double a short shower, but the gap closes fast. A 16-minute shower with a 2.5 gpm head uses the same 40 gallons as the bath and costs the same. The bath vs. shower water calculator lets you compare your own habits.

Bath costs over time

A single bath is cheap, which makes it easy to ignore the annual total. These examples use the example rates and a 40-gallon fill unless noted:

How to lower the cost of a bath

• Run less water. Because your body displaces water, you can fill the tub shallower than you'd expect. Each 10 gallons you skip saves roughly 18 to 30 cents.
• Lower the bath temperature slightly. A few degrees cooler trims the heating cost by around 10% per 5 °F.
• Check your drain stopper. A stopper that leaks lets warm water escape, tempting you to run the tap again to top it up.
• Consider a heat pump water heater. If you take baths often and use electric resistance heating, it cuts the heating share of the bill the most.
• Know your rates. If your utility prices sewer on winter water use or has tiered pricing, knowing where your baths fall can change when and how often they make sense.

The bottom line

A standard 40-gallon bath costs roughly $1.20 with an electric heater and $0.70 with gas, at the example rates used here. Water and sewer take a fixed share, and heating takes the rest, with fuel type, season and tub size doing most of the moving. A bath costs about twice a short shower, but a long shower can match it. For an exact figure, plug your own rates and temperatures into the calculator.