About the Pool Cover Savings
This calculator estimates how many gallons of water a pool cover saves over a season by comparing evaporation with and without the cover in place. It is intended for pool owners deciding whether a cover is worth the cost and effort, expressed in terms of water they would otherwise need to refill.
How It Works
You enter your pool's surface area, its typical evaporation rate in inches per week when uncovered, and how many weeks per year you would realistically keep it covered. The calculator first works out how much water an uncovered pool loses to evaporation over those weeks, then applies a fixed reduction rate representing how effectively a cover blocks evaporation to estimate the gallons actually saved.
Formula & Methodology
The 0.623 conversion factor turns an evaporation depth, inches lost per week spread evenly over the pool's surface, into gallons, since one inch of water depth over one square foot of surface equals about 0.623 gallons. Multiplying that by pool area gives the total weekly evaporation volume for an uncovered pool. The calculator then assumes a cover blocks 92% of that evaporation while it is in place, a figure in the middle of the commonly cited 90-95% range for a well-fitted pool cover, and multiplies the weekly saved volume by the number of weeks you actually keep the pool covered to get a seasonal total.
Examples
Typical backyard pool
At the default 450 sq ft pool, 2 in/wk evaporation, and 30 weeks covered, uncovered weekly loss is about 561 gallons, and the cover saves an estimated 15,475 gallons over the season.
Larger pool, shorter covered season
At an 800 sq ft pool, 1.5 in/wk evaporation, and 20 weeks covered, weekly uncovered loss is about 748 gallons, saving roughly 13,756 gallons over the covered weeks.
Advantages
- Converts an abstract evaporation rate into a concrete gallons-saved figure tied to your pool's actual size and covering schedule.
- Makes it easy to see how much the number of weeks covered, not just the cover itself, drives total water savings.
- Uses a single evaporation-blocking rate of 92%, grounded in the commonly cited range for fitted pool covers, rather than an arbitrary guess.
Common Mistakes
- Using a national average evaporation rate instead of one appropriate to local climate, wind exposure, and sun exposure, which can be off by a wide margin.
- Assuming the cover is on for the full year without accounting for swim season, when the pool is actually uncovered and in use for much of the year.
- Overlooking that the water savings shown do not include the separate heat-retention benefit a cover provides for heated pools, which adds further savings on the energy side.
Edge Cases to Watch For
- The 92% reduction rate assumes a properly fitted, intact cover; a loose, torn, or partially removed cover would save meaningfully less than shown.
- Evaporation rate itself varies with wind, humidity, sun exposure, and water temperature, so the figure you enter should reflect your specific pool and climate rather than a generic average if you want an accurate result.
- Weeks covered is treated as a simple average; a pool covered every night but uncovered during the day would need a different weekly evaporation rate entered to reflect that partial coverage pattern accurately.
Common Use Cases
- Pool owners in drought-prone or water-restricted areas evaluating whether to buy a cover.
- Homeowners comparing water costs against the upfront and ongoing cost of a cover system.
- Property managers overseeing shared or community pools looking to reduce water and chemical replacement costs.