If you’ve shopped for a pool heat pump recently, you’ve probably seen brands advertising COP numbers like 13, 15, or even all the way up to 20x. On paper, that sounds like unbeatable efficiency.
The problem is that COP numbers are easy to make look impressive if you don’t explain how they were measured.
COP, or Coefficient of Performance, is a real efficiency metric. But it is not a single fixed score that a heat pump delivers all the time. COP changes with air temperature, humidity, and pool conditions. So a huge COP claim without test details is usually more marketing than meaning.
In this guide, we’ll break down:
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what COP actually is
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how it changes in real life
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why some brands show inflated numbers
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and how to compare heat pumps honestly
By the end, you’ll know exactly what COP to trust, and what to ignore.
What COP means in plain English
COP stands for Coefficient of Performance. It is the simplest way to describe heat pump efficiency.
COP = heat energy delivered ÷ electricity used
So if a heat pump is running at:
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COP 3, it delivers about 3 units of heat for every 1 unit of electricity.
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COP 6, it delivers about 6 units of heat for every 1 unit of electricity.
Heat pumps can do this because they do not “create” heat like a toaster or gas burner. They move heat from the air into the pool, so the heat output can be several times larger than the electrical input.
COP is not a constant number
A big misunderstanding in pool heating is thinking COP is a fixed rating that a heat pump delivers all the time. It is not.
COP changes with conditions, especially:
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air temperature
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humidity
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water temperature
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wind and heat loss rate
When the air is warm and humid, there is more usable heat to pull from the environment. COP goes up. When the air is cooler or drier, COP goes down.
A typical example from industry data:
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around COP 6 at 80°F air with high humidity
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closer to COP 4 around 50°F air
That day-to-day swing is normal heat pump behavior.
What realistic COP looks like for pool owners
For most residential pool heat pumps, real-world COP typically lands in the 3 to 6 range across a season, depending on climate and use habits.
In perfect summer conditions, well-designed inverter models can run above that for stretches. But over the whole season, 3 to 6 is what most owners should expect to see.
So when you see a product claiming COP 13 to 15 as if it is normal, it should raise a flag.
How some brands get COP 13 to 15x on paper
A lot of the new low-cost competitors on Amazon are using a common marketing move: they publish a best-case lab COP without explaining the test conditions.
Two ways this happens:
A. Testing in extremely favorable air conditions
COP rises sharply in very warm, very humid air. A unit tested in those conditions can show huge numbers, even though that is not how most pools are heated day to day.
B. Using a different rating point than North American standards
In the U.S., pool heat pumps are compared under AHRI Standard 1160, which defines required test procedures and published ratings.
That standard includes well-known rating points like:
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80/80/80 meaning 80°F air, 80°F water, 80% humidity
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80/63/80 meaning 80°F air, 80°F water, 63% humidity
If a brand does not publish AHRI ratings, or test conditions warranted by certifying bodies like UL/ETL/SGS/CSA, they may be using a different test point that makes the heater look far more efficient on a spec sheet than it will be in normal use.
What matters more than a single COP number
A single COP value is only a snapshot. What pool owners care about is season-long heating cost and comfort.
That depends on:
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COP across a range of air temperatures, not just one point
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how well the unit maintains temp once warm
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your pool’s heat loss rate
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cover use, wind exposure, and shade
For example, evaporation alone can remove heat extremely fast. Each pound of water that evaporates takes about 1,048 BTU out of the pool. That is why covers make such a dramatic difference in real performance.
So even a very “high COP” heat pump will perform poorly on an uncovered, windy, heat-leaking pool.
Bottom line
COP is a real efficiency metric, and it is one of the reasons heat pumps are such a cost-effective way to heat a pool.
But COP is only meaningful when you know the test conditions.
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Most real-world pool heat pumps operate around COP 3 to 6 across normal conditions.
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COP values like 13 to 15 are almost always best-case lab snapshots, not everyday performance.
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AHRI-verified ratings under Standard 1160 are the safest way to compare models honestly.
If you want lower heating costs, the real winning combo is still: a properly sized heat pump, realistic expectations about weather, and consistent cover use.
