Thinking about adding a heat pump to your pool setup? Great move—heat pumps are energy-efficient, reliable, and can extend your swim season comfortably. But here’s the catch: size matters. Too small, and your pool will take forever to warm up. Too big, and you’ll spend more upfront than necessary. So how do you size a pool heat pump just right? Let’s break it down.
Why Proper Sizing Is Crucial
A properly sized heat pump ensures:
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Efficient heating without driving up energy bills
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Faster temperature recovery after cold nights or rain
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Longer equipment life by avoiding constant cycling
It’s not just about pool size—it’s about your location, climate, and how you use your pool.
Step 1: Know Your Pool's Volume
Start with the basics: pool volume in gallons. Here's a quick cheat sheet:
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Rectangular Pool:
Length x Width x Average Depth x 7.5 = Gallons -
Round Pool:
Diameter x Diameter x Average Depth x 5.9 = Gallons -
Oval Pool:
Length x Width x Average Depth x 6.7 = Gallons
Knowing the total gallons helps you estimate how much water the heat pump needs to warm up.
Step 2: Consider Your Desired Temperature Rise
Are you hoping to keep your pool at 85°F when the ambient temperature is 70°F? That’s a 15-degree rise. The greater the temperature difference, the more powerful your heat pump needs to be.
Pro tip: Heat pumps work best in warmer ambient temps (above 50°F), so if you live in a cooler region, sizing slightly larger may be necessary.
Step 3: Calculate Required BTUs
BTU stands for British Thermal Unit, which measures heat energy. Here's a basic formula:
Pool Gallons x 8.34 (weight of 1 gallon of water) x Desired Temperature Rise ÷ 24 = BTUs per hour
Example:
For a 20,000-gallon pool and a 15°F temperature rise:
20,000 x 8.34 x 15 ÷ 24 ≈ 104,250 BTUs/hour
This means you’d want a heat pump that delivers at least 100,000 BTUs/hour.
Step 4: Factor in Location and Pool Use
You’ll also want to adjust for:
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Climate: Warmer climates need less power; cooler areas may need more.
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Wind exposure and shading: These can cool your pool quickly.
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Pool cover usage: Using a solar cover drastically reduces heat loss.
In windy or shaded areas, or if you skip the cover, go up a size for efficiency.
Step 5: Match Your Heat Pump to the Specs
Once you’ve got your target BTUs, match them to a heat pump model. PoolPartsToGo.com carries a variety of reliable options. A few quick guidelines:
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Small pools (10,000–15,000 gallons): Look for 50,000–75,000 BTU units
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Medium pools (15,000–25,000 gallons): 90,000–120,000 BTUs
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Large pools (25,000+ gallons): 120,000–140,000+ BTUs
Final Tips for Sizing Success
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Don’t undersize—you’ll pay more in run time and energy use.
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Oversizing slightly is okay, especially in cooler or high-use scenarios.
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Use a pool cover to retain heat, no matter your pump size.
Wrap-Up
Sizing a pool heat pump isn’t just plug-and-play, but it doesn’t have to be complicated. With a little math and consideration of your environment, you can choose a unit that keeps your pool comfy without blowing your budget. When in doubt, consult with experts—or check out the heat pump options at PoolPartsToGo.com, where specs are easy to compare.
Want help calculating the perfect size for your pool? Just ask—we’re here to help you swim smart.
