Quick Answer: How Much Does It Cost to Heat a Pool?

The cost of heating a swimming pool depends on the heater type, local energy prices, pool size, desired temperature increase and ongoing heat loss. There is no single hourly or monthly cost that applies to every pool.

For example, at hypothetical utility rates, a 400,000-BTU/hr natural gas heater costs approximately $6 per hour in fuel at $1.50 per therm. A heat pump drawing 5 kW costs $0.90 per hour in electricity at $0.18 per kWh. These heaters may deliver very different amounts of useful heat, so their hourly costs are not a direct efficiency comparison.

To estimate your own expense, calculate the energy required to heat your pool, determine your heater's actual energy consumption and apply your local utility rate. Then account for ongoing heat loss and the number of hours you expect to operate the equipment.

Pool Heating Cost at a Glance

The following examples use hypothetical energy prices and assume continuous operation at the stated input. They are not current national averages or product-specific operating-cost estimates.

These figures estimate energy cost while the equipment is operating. They do not account for differences in useful heating output, additional circulation-pump electricity, installation, maintenance or fixed utility charges.

What Determines Pool Heating Cost?

The major variables include:

• Pool heater type.
• Heater input or electrical consumption.
• Energy price.
• Daily runtime.
• Pool size and surface area.
• Desired water temperature.
• Outdoor temperature and humidity.
• Wind and evaporation.
• Whether the pool is covered.

Two pools with identical heaters can have very different heating bills because their owners maintain different temperatures, live in different climates or use different heating schedules.

For a broader explanation of heater types, sizing, heating performance and operating costs, see our Complete Guide to Pool Heaters.

Natural Gas Pool Heater Cost

Natural gas is commonly billed by the therm. One therm represents 100,000 BTU of fuel energy.

A simplified fuel-use calculation is:

Heater Fuel Input (BTU/hr) ÷ 100,000 = Therms per Hour

Multiply the result by your utility's applicable price per therm.

Example: A 400,000-BTU/hr Gas Heater

Suppose a gas heater has a rated fuel input of 400,000 BTU/hr.

400,000 ÷ 100,000 = 4 therms/hour

At a hypothetical natural gas price of $1.50 per therm:

4 × $1.50 = $6.00/hour

If the heater fires continuously for four hours:

$6.00 × 4 = $24.00

The estimated fuel cost is $24 for that heating period.

How Natural Gas Prices Change the Cost

The following table assumes a 400,000-BTU/hr heater fires continuously for four hours and consumes 16 therms.

Use the applicable cost of additional gas consumption from your utility bill. Depending on your billing structure, variable delivery charges and other fees may affect the actual cost.

Propane Pool Heater Cost

Propane is generally purchased by the gallon. A gallon of propane contains approximately 91,500 BTU.

A simplified consumption estimate is:

Heater Fuel Input (BTU/hr) ÷ 91,500 = Approximate Gallons per Hour

Multiply the result by your delivered propane price.

Example: A 400,000-BTU/hr Propane Heater

Suppose a propane heater has a rated fuel input of 400,000 BTU/hr.

400,000 ÷ 91,500 = approximately 4.37 gallons/hour

At a hypothetical delivered propane price of $3.00 per gallon:

4.37 × $3.00 = approximately $13.11/hour

Four hours of continuous firing would consume approximately 17.49 gallons and cost about $52.46 in fuel.

Propane Cost at Different Delivered Prices

These are hypothetical prices, not current delivered propane quotes.

If you're considering gas or propane heating, compare heater capacities and fuel requirements along with purchase price before selecting equipment.

Compare Gas Pool Heaters on Amazon

Heat Pump Pool Heater Cost

Heat pumps use electricity to transfer heat from outdoor air into pool water.

Their specifications typically include electrical input, heating output and coefficient of performance (COP).

The basic operating-cost calculation is:

Electrical Input (kW) × Operating Hours × Electricity Rate ($/kWh) = Operating Cost

Example: A Heat Pump Drawing 5 kW

Suppose a heat pump consumes 5 kW while operating.

If it runs for six hours:

5 × 6 = 30 kWh

At a hypothetical electricity rate of $0.18/kWh:

30 × $0.18 = $5.40

The estimated electricity cost is $5.40 for that operating period.

Heat Pump Cost by Daily Runtime

The following table assumes a constant 5 kW electrical input and an electricity rate of $0.18/kWh.

This table assumes the same runtime every day for 30 days. Real heating schedules and electrical consumption vary.

Heat-pump performance changes with outdoor temperature, humidity and pool-water temperature, so actual cost cannot be determined from nameplate heating capacity alone.

For a closer comparison of electricity and fuel economics, see Pool Heat Pump vs. Gas Heater Operating Cost.

When comparing heat pumps, consider heating capacity and efficiency together with your local electricity rate and expected operating conditions.

Compare Pool Heat Pumps on Amazon

Compare the Cost of Delivering the Same Amount of Heat

Comparing hourly energy costs alone can be misleading because different heaters may deliver substantially different amounts of useful heat.

For a more meaningful comparison, calculate the cost of delivering the same quantity of heat to the pool.

Illustrative Comparison: 100,000 BTU of Useful Heat

Assume the following hypothetical conditions:

• Electricity costs $0.18/kWh.
• Natural gas costs $1.50/therm.
• Propane costs $3.00/gallon.
• Heat-pump COP is 5.
• Gas-heater thermal efficiency is 84%.

This comparison isolates energy costs for the same useful heat output. It excludes installation, maintenance, additional circulation-pump electricity and other ownership expenses.

Actual results depend on your local energy prices and the equipment's performance under your operating conditions.

Example: Cost to Raise a 15,000-Gallon Pool by 10°F

To estimate the cost of an initial temperature increase, first calculate how much heat the pool needs.

A simplified formula is:

Required Heat (BTU) = Pool Gallons × 8.34 × Temperature Increase (°F)

For a 15,000-gallon pool and a 10°F increase:

15,000 × 8.34 × 10 = 1,251,000 BTU

The pool requires approximately 1.25 million BTU of useful heat before accounting for environmental heat loss.

Hypothetical Initial Heat-Up Costs

Using the same hypothetical energy prices and efficiency assumptions from the previous example:

These figures represent theoretical energy costs for delivering the required heat. Real-world costs will be higher if the pool loses heat while it is warming.

The calculation also assumes constant heater efficiency and excludes additional circulation-pump electricity.

Why Pool Heating Costs Vary by Climate

The larger the difference between the desired pool temperature and surrounding conditions, the harder the heating system generally has to work.

Wind and evaporation can increase heat loss significantly.

Heat pumps are additionally affected by outdoor temperature and humidity because those conditions influence how efficiently they collect heat from the air.

Example: Heating During Different Seasons

Consider an outdoor pool maintained at 82°F.

During warm weather, the pool may receive substantial solar heat and experience relatively small temperature differences between the water and surrounding air.

During cooler weather, the same pool may lose heat more quickly, particularly overnight or in windy conditions.

The heater must replace whatever heat the pool loses to maintain the selected temperature.

This is why a single hourly cost estimate cannot reliably predict an entire season's heating bill without information about runtime and weather.

A Pool Cover Can Make a Major Difference

Evaporation is a major source of pool heat loss. Reducing evaporation with a properly used pool cover can therefore reduce heating demand substantially.

The amount saved depends on the pool's surface area, weather, cover type, water temperature and how consistently the cover is used.

Example: Reducing Daily Heat Loss

Suppose an uncovered pool loses a hypothetical 300,000 BTU of heat per day.

If a cover and other operating conditions reduce that loss to 150,000 BTU per day, the heater needs to replace approximately half as much heat to maintain the same temperature.

At a hypothetical energy cost of $1.50 per 100,000 useful BTU:

These are hypothetical heat-loss values used to illustrate the calculation, not measured savings for a particular cover.

Heating From Cold vs. Maintaining Temperature

There are two different heating jobs.

Initial heat-up requires raising the temperature of the entire body of water.

Temperature maintenance requires replacing the heat that continually escapes from the pool.

A pool that is repeatedly allowed to cool and reheated can therefore have a different cost profile from a pool maintained near a constant temperature.

Initial Heat-Up Example

A 15,000-gallon pool requires approximately 125,100 BTU of useful heat for each 1°F temperature increase.

Raising it by 8°F requires:

125,100 × 8 = 1,000,800 BTU

That represents the theoretical energy needed to warm the water, excluding ongoing heat loss.

Temperature Maintenance Example

Suppose the same pool loses an illustrative 200,000 BTU over a particular day.

Maintaining its temperature requires replacing approximately that amount of heat, assuming no additional solar or other heat gains.

Actual daily heat loss can vary substantially with weather and pool-cover use.

See How Long Does It Take to Heat a Pool? for more about how pool volume, heater output, temperature increase and heat loss affect runtime.

How Heater Size Affects Operating Cost

Heater capacity influences how quickly heat can be delivered to the pool.

A higher-output heater may consume more energy per hour but complete the initial heating job in less time.

That means a larger heater does not automatically cost proportionally more to perform the same heating job.

Example: Two Gas Heaters With the Same Efficiency

Suppose two hypothetical gas heaters both operate at 84% thermal efficiency.

With identical thermal efficiency and no heat loss, both heaters require approximately the same fuel energy to deliver the same amount of useful heat.

In a real outdoor pool, the longer heating period may expose the water to additional heat loss, so actual costs can differ.

See What Size Pool Heater Do I Need? for the sizing process, or use our Pool Heater Sizing Calculator for a starting estimate.

Don't Forget Circulation-Pump Electricity

Pool heaters require appropriate water circulation while operating.

If heating requires the circulation pump to run longer or at a higher speed than it otherwise would, the additional pump electricity should be included in the heating-cost estimate.

Example: Additional Pump Runtime

Suppose heating requires four additional hours of pump operation at an electrical input of 600 watts.

0.6 kW × 4 hours = 2.4 kWh

At $0.18/kWh:

2.4 × $0.18 = $0.43

The additional circulation cost is approximately $0.43 for that hypothetical heating period.

Do not count the pump's entire electricity consumption as an additional heating expense if it would have operated at the same speed and for the same duration without heating.

How to Estimate Your Own Pool Heating Cost

1. Identify your heater type. Determine whether you use natural gas, propane or an electric heat pump.
2. Find the equipment's specifications. For gas heaters, identify fuel input and thermal efficiency. For heat pumps, identify electrical input, heating capacity and relevant COP.
3. Check your current energy price. Use the applicable electricity rate, natural gas price or delivered propane price.
4. Calculate the initial heating requirement. Use pool volume and the desired temperature increase.
5. Estimate heating time. Divide required heat by useful heater output, then allow for environmental heat loss.
6. Calculate energy consumption. Apply the equipment's electrical or fuel-input rating to the expected operating time.
7. Account for temperature maintenance. Consider how frequently the heater will need to replace ongoing heat loss.
8. Include additional operating expenses. Account for any additional circulation-pump electricity and relevant variable utility charges.

You can also enter your equipment and energy-rate information into our Pool Heater Operating Cost Calculator to estimate operating expense.

Ways to Reduce Pool Heating Cost

• Use a pool cover when practical. Reducing evaporation can lower the amount of heat the heater must replace.
• Avoid unnecessarily high water temperatures. Higher target temperatures can increase heat loss and heating requirements.
• Reduce excessive wind exposure where practical. Wind can increase evaporation and heat loss.
• Maintain the heater and circulation system. Follow manufacturer requirements for water flow, cleaning and equipment maintenance.
• Use an appropriate heating schedule. Account for heater type, weather, desired swimming times and energy pricing.
• Compare local electricity and fuel prices. Use actual utility rates rather than generic averages when evaluating equipment.
• Consider time-of-use electricity pricing. If your utility has different rates throughout the day, heating schedules may affect operating costs.

Frequently Asked Questions

How much does it cost to run a gas pool heater for one hour?

Divide its BTU/hr fuel-input rating by 100,000 to estimate therms per hour, then multiply by your natural gas rate. For example, a 400,000-BTU/hr heater consumes approximately four therms per hour and costs $6 per hour in fuel at $1.50 per therm.

How much does it cost to run a pool heat pump for eight hours?

Multiply its electrical input in kilowatts by eight hours and your electricity rate. A heat pump drawing 5 kW uses 40 kWh in eight hours, costing $7.20 at $0.18/kWh.

How much does propane pool heating cost?

Divide the heater's BTU/hr fuel-input rating by approximately 91,500 to estimate gallons per hour, then multiply by your delivered propane price. Actual cost depends on heater input, runtime and local pricing.

How much does it cost to heat a 10,000-gallon pool?

It depends on the temperature increase, heater efficiency, energy price and heat loss. A 10,000-gallon pool requires approximately 834,000 BTU of useful heat for a theoretical 10°F increase.

How much does it cost to heat a 20,000-gallon pool?

A 20,000-gallon pool requires approximately 1,668,000 BTU of useful heat for a theoretical 10°F increase. Apply your heater's efficiency and local energy rate, then account for heat loss during heating.

Is it cheaper to leave a pool heater running or turn it off?

The result depends on the heater type, pool-cover use, weather, energy pricing and how frequently the pool is used. Maintaining a higher water temperature generally increases ongoing heat loss, but reheating time and equipment performance also matter when planning a practical operating schedule.

Does a pool cover reduce heating costs?

A suitable cover can reduce evaporation and other heat losses, lowering the amount of energy needed to maintain the desired water temperature. Actual savings depend on the pool and operating conditions.

Does a bigger pool heater cost more to run?

A higher-input heater generally consumes more energy per hour, but it may complete the same heating job in less time. Compare efficiency and total energy required rather than hourly consumption alone.

Why is my pool heating bill higher in cooler weather?

Cooler conditions can increase heat loss. Heat pumps may also deliver less heat and operate at lower efficiency as outdoor conditions change.

Can I estimate monthly pool heating costs?

Yes. Estimate the heater's energy consumption during your expected daily operating schedule, multiply by your applicable energy rate and then by the number of operating days. Account for weather-related changes in runtime and performance.

Bottom Line

There is no useful single answer to what it costs to heat every swimming pool. Two identical pools can have very different heating bills because of climate, utility rates, heat loss and operating habits.

Start with your heater's actual energy consumption and your local utility rate. For a more complete estimate, calculate the energy required for initial heat-up, account for ongoing temperature maintenance and include any additional circulation-pump electricity.