01
The purpose
What does this calculator estimate?
How fast your pool sheds heat to evaporation, wind, and air — and how much a cover saves.
Heating & Energy · D5
Pool Heat Loss Rate Calculator
How fast your pool sheds heat to evaporation, wind, and air — and how much a cover saves.
Measure the inputsEvaporation is the number-one way pools lose heat — usually well over half the total.
Read the full resultWind multiplies evaporative loss; a windbreak can cut heating costs noticeably.
Check the boundaryA solar or solid cover is the single most cost-effective heat-saving upgrade.
Useful forHeating & EnergyPlanningComparisonVerification
Live calculation
Heat loss inputs
✓ Checked May 2026
Enter surface area, temps, wind, and cover.
Calculated result
—
Enter the required values to calculate.
Enter the known values. Let the engine handle the calculation.
✓ Formula checked↻ Live result○ No account needed
Planning estimate only. Confirm product labels, equipment specifications, qualified-professional advice and local requirements before acting.
The result, explained
Use the Pool Heat Loss Rate Calculator result with context.
How fast your pool sheds heat to evaporation, wind, and air — and how much a cover saves.
02
The tool
What information does it use?
- Pool surface area: enter a measured or verified value
- Water temp: enter a measured or verified value
- Air temp: enter a measured or verified value
- Wind speed: Wind dramatically increases evaporative loss.
- Humidity: %
- Cover type: None, solar bubble, solid, or liquid.
03
The method
How to use this calculator
- Pool surface areaEnter the value you can verify.
- Water tempEnter the value you can verify.
- Air tempEnter the value you can verify.
- Wind speedWind dramatically increases evaporative loss.
- Humidity%
- Cover typeNone, solar bubble, solid, or liquid.
04
The relationship
The formula in plain English
Total loss = evaporation + convection + radiation, then × cover factor
Evaporation is the biggest loss and rises with wind. A solar cover cuts total loss ~65%.05
Worked through
A worked example: 500 sq ft pool, 82°F water, 65°F air, 5 mph wind, no cover
- Temp diff = 82 − 65 = 17°F
- Evap = 500×17×0.4×(1+0.115×5) ≈ 5,355 BTU/hr
- + convection 1,700 + radiation 850 ≈ 7,905 BTU/hr
| Condition | Wind | Cover | Heat loss BTU/hr |
|---|---|---|---|
| Calm, uncovered | 0 mph | None | ~5,950 |
| Light wind | 5 mph | None | ~7,663 |
| Breezy | 10 mph | None | ~9,378 |
| Light wind | 5 mph | Solar cover | ~2,682 |
| Breezy | 10 mph | Solar cover | ~3,282 |
06
Why it matters
How the result supports the next decision
Evaporation is the number-one way pools lose heat — usually well over half the total.
Wind multiplies evaporative loss; a windbreak can cut heating costs noticeably.
07
Good inputs
Improve the estimate before relying on it
- Evaporation is the number-one way pools lose heat — usually well over half the total.
- Wind multiplies evaporative loss; a windbreak can cut heating costs noticeably.
- A solar or solid cover is the single most cost-effective heat-saving upgrade.
- Heat loss is worst on cool, dry, windy nights — exactly when you want a cover on.
- Lower the water temperature a couple of degrees and loss drops along with cost.
08
The boundary
How to interpret the result
Measurements, equipment specifications, site conditions and local requirements can change the practical result.
The engine reports invalid inputs and safety warnings beside the result. Resolve those messages before using the estimate.
09
Before acting
What should override this estimate?
- Measured site conditions and current test results
- Product labels and manufacturer specifications
- Qualified-professional advice and applicable local codes
10
Common questions
Frequently asked questions
How does a pool lose heat?
Through three paths: evaporation, convection, and radiation. Evaporation is by far the largest, typically more than half the total loss, because turning water to vapor carries away a lot of energy. Convection is heat carried off by air moving over the surface, and radiation is infrared heat emitted to the cooler sky.
Why is evaporation the biggest heat loss?
Evaporating water absorbs a large amount of energy — its latent heat of vaporization — and that energy leaves with the vapor. On a warm pool exposed to dry, moving air, evaporation can account for the majority of total heat loss, which is exactly why covering the surface saves so much energy.
How much does wind increase heat loss?
Significantly. Wind sweeps humid air away from the surface and replaces it with drier air, accelerating evaporation. Even a light breeze raises evaporative loss noticeably, and strong wind can multiply it. A solid fence, hedge, or windbreak around the pool reduces this and lowers heating bills.
How much heat does a cover save?
A solar bubble or solid cover typically cuts total heat loss by around 65 percent, because it stops evaporation — the dominant loss — almost entirely. A liquid cover is far weaker, reducing loss only modestly. For overnight retention, a physical cover is the most effective option by a wide margin.
Does humidity affect pool heat loss?
Yes. Evaporation slows as the surrounding air gets more humid, because the air can hold less additional moisture. So a pool loses heat faster on a dry night than a humid one at the same temperature and wind. Dry, breezy, cool conditions produce the worst heat loss.
What is the biggest source of pool heat loss?
Evaporation — usually more than half of total heat loss from an uncovered pool.
How do I reduce pool heat loss?
Use a cover, add a windbreak, and lower the set temperature slightly — covers help the most.
Does a pool lose more heat at night?
Yes — cooler night air and clear skies increase convective and radiative loss, so covering overnight helps most.
Primary sources
Use the result with current guidance.
These official references support safe planning context. Product labels, local requirements and qualified-professional advice take priority over a general calculator estimate.