Pool Heat Time Calculator

We’ve designed pool heat time calculator to estimate the duration required to heat a swimming pool to a desired temperature.

This how long does it take to heat a pool calculator takes into account various factors such as pool volume, current water temperature, target temperature, and the heating system’s capacity. By inputting these parameters, pool owners can obtain a reasonably accurate estimate of the time needed to warm their pool.

Consider a scenario where you have a 15,000-gallon pool currently at 70°F (21°C), and you want to raise the temperature to 82°F (28°C) using a 100,000 BTU/hour heater. The calculator would process these inputs and provide an estimated heating time, helping you plan your pool activities more effectively.

Pool Size (gallons)	Initial Temp (°F)	Target Temp (°F)	Heater Output (BTU/hr)	Efficiency	Heating Time (hours)
15,000	65	80	100,000	80%	24.8
15,000	70	85	100,000	85%	20.5
20,000	70	82	125,000	80%	20.4
20,000	75	85	125,000	90%	14.9
25,000	68	80	150,000	85%	25.2
25,000	70	90	175,000	80%	31.3
30,000	60	80	200,000	90%	30.0
30,000	72	88	200,000	85%	26.5
35,000	60	82	200,000	90%	38.5
35,000	65	75	250,000	95%	17.2
40,000	70	85	250,000	90%	35.2
40,000	75	90	300,000	95%	27.7
50,000	68	78	300,000	95%	21.9
50,000	70	85	350,000	90%	31.3
60,000	65	75	400,000	85%	34.4
60,000	70	80	400,000	90%	25.8

Pool Heat Time Calculation Formula

The formula for calculating pool heating time is:

Time (hours) = (Volume × Weight × Specific Heat × Temperature Difference) / (Heater Output × Efficiency)

Where:

Volume: Pool water volume in gallons
Weight: Weight of water (8.34 lbs per gallon)
Specific Heat: Specific heat of water (1 BTU/lb/°F)
Temperature Difference: Target temperature minus current temperature (°F)
Heater Output: Heater capacity in BTU/hour
Efficiency: Heater efficiency (typically 0.75-0.95)

Suppose you have a 20,000-gallon pool at 65°F that you want to heat to 80°F using a 150,000 BTU/hour heater with 85% efficiency.

Time = (20,000 × 8.34 × 1 × (80 - 65)) / (150,000 × 0.85)
    = 2,501,000 / 127,500
    ≈ 19.6 hours

How do you calculate how long it takes to heat a pool?

To calculate the heating time for a pool, follow these steps:

Measure the pool volume in gallons
Determine the current water temperature
Decide on the target temperature
Check the heater’s BTU rating
Estimate the heater’s efficiency (consult the manufacturer’s specifications)
Apply the formula mentioned earlier

For instance, let’s calculate the heating time for a 30,000-gallon pool, currently at 68°F, aiming for 84°F, using a 200,000 BTU/hour heater with 90% efficiency:

Time = (30,000 × 8.34 × 1 × (84 - 68)) / (200,000 × 0.90)
    = 5,004,000 / 180,000
    ≈ 27.8 hours

How long does it take to heat a pool from 60 to 80?

With a 25,000-gallon pool with a 175,000 BTU/hour heater operating at 80% efficiency:

Time = (25,000 × 8.34 × 1 × (80 - 60)) / (175,000 × 0.80)
    = 4,170,000 / 140,000
    ≈ 29.8 hours

This calculation shows that heating a large pool by 20°F can take more than a day, highlighting the importance of planning ahead and considering energy costs.

How long does it take to heat a 20,000-gallon pool?

Let’s assume we want to heat a 20,000-gallon pool from 70°F to 85°F using a 125,000 BTU/hour heater with 85% efficiency:

Time = (20,000 × 8.34 × 1 × (85 - 70)) / (125,000 × 0.85)
    = 2,502,000 / 106,250
    ≈ 23.5 hours

How long to heat a pool by 10 degrees?

With a 35,000-gallon pool with a 250,000 BTU/hour heater at 95% efficiency:

Time = (35,000 × 8.34 × 1 × 10) / (250,000 × 0.95)
    = 2,919,000 / 237,500
    ≈ 12.3 hours

How many kW is needed to heat a pool?

As a rule of thumb, a pool typically requires 10 BTU per hour per gallon of water to heat effectively.

For example, a 40,000-gallon pool would need approximately 400,000 BTU/hour. To convert this to kW:

kW = BTU/hour ÷ 3,412

400,000 ÷ 3,412 ≈ 117 kW

A 40,000-gallon pool would require about 117 kW of heating power for optimal performance.

References

U.S. Department of Energy – Energy Saver: Swimming Pool Heating https://www.energy.gov/energysaver/swimming-pool-heating

Related Tools:

Pool Heat Time Calculator – How Long Does It Take To Heat A Pool