How long does it take to heat a pool?

How long it takes to heat a pool depends on the heater, the size of the pool, the weather and how much heat the water loses while it warms. A gas heater can raise the temperature noticeably within hours, while a heat pump often needs a day or more to bring a pool up from cool water.

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How long to heat a pool: typical times

These are rough ranges for a properly sized heater on a residential pool. Your pool may be faster or slower.

Gas heater, pool: often about 1 to 3 degrees an hour, depending on the heater and the pool’s volume, so a 10-degree rise can take several hours to most of a day.
Heat pump, pool: often about half a degree to a degree and a half an hour in mild weather, so a 10-degree rise commonly takes one to three days once overnight losses are counted.
Spa: a spa holds far less water, so a gas heater can often bring it up in under an hour and a heat pump in roughly one to a few hours.

You can estimate your own pool. Warming one pound of water by one degree takes about one BTU, and a gallon of water weighs about 8.3 pounds. A 15,000-gallon pool needs roughly 125,000 BTUs for every degree, before counting the heat lost to the air. Compare that with the heater’s rated output and you’ll see why size matters.

What makes a pool heat faster or slower

Heater type and size: output in BTUs is the biggest factor. An undersized heater can run all day and barely keep up.
Pool size: more gallons take more heat. Spas heat quickly because they hold so little water.
Starting temperature: a 10-degree rise takes roughly twice as long as a 5-degree rise.
Air temperature and wind: heat pumps lose output as the air cools, and wind strips heat from the water surface.
Cover or no cover: most heat is lost through evaporation at the surface, especially overnight. A solar cover is the single biggest help.
Water features: spillways, waterfalls and fountains increase evaporation and heat loss while they run.
Pump run time and flow: the heater only works while the pump runs with enough flow. A short schedule or a dirty filter slows heating.
Sun and shade: a pool in full sun gains free heat during the day, while a shaded pool relies more on the heater.

If the heater runs but the temperature doesn’t move at all, the problem may be the heater itself. See why a pool heater isn’t heating.

How to heat your pool faster

Use a solar cover whenever the pool isn’t in use, especially overnight.
With a heat pump, start heating a day or two before you plan to swim.
Run the pump long enough for the heater to work, and keep the baskets and filter clean.
Turn off spillways and water features while the pool is heating.
Run a heat pump during the warmest part of the day when you can.
Set the thermostat to the temperature you want rather than the maximum. A higher setting doesn’t heat any faster.
Have the heater serviced before the season so it delivers its full output.

Keeping a pool warm through a South Florida winter

Many pools in northern Palm Beach County are heated from about November through March. For a pool used often, holding a steady temperature with a heat pump and a cover is usually more practical than reheating from cold each weekend, because a heat pump recovers slowly. If you swim only occasionally, heating on demand with gas may cost less overall.

Choosing between the two? Our comparison of a heat pump and a gas pool heater covers running costs, cold snaps and salt air, and our pool heater installation and repair page explains how we size and quote a new heater.

Pool heating time questions

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

That’s a 20-degree rise, a big job for any heater. A gas heater might take most of a day to two days on a typical residential pool, and a heat pump several days, depending on size, weather and whether the pool is covered. Pools here rarely get that cold, so most heating is a smaller rise.

How can I heat up my pool quickly?

A gas heater is the fastest option. With any heater, use a cover, turn off water features, run the pump while heating and keep the filter clean.

Is 72-degree pool water too cold?

Many people find 72°F cool for relaxed swimming. Residential pools are often kept somewhere around 78 to 84°F, but it comes down to preference and how active you are in the water.

How many hours a day should a pool heat pump run?

While it’s bringing the pool up to temperature, a heat pump may need to run most of the day. Once the pool is warm, it runs only as needed to replace lost heat, which depends on the weather and whether you use a cover.

Does a pool heat up faster with a cover on?

Yes. A cover reduces evaporation, where most heat is lost, so more of the heater’s output goes into raising the temperature instead of replacing heat that escaped.

Let’s find the right next step

Get Wet Pools serves Jupiter, North Palm Beach, Tequesta and nearby communities. Tell us about your pool, spa and current heater, and we’ll help you get it warm when you want to swim.

Request a Heater Estimate Call 561-574-6246