Why do most therapy pools close? Is it lack of patient interest? Pool water quality? Need for space for other offices? No. It's because pools can hemorrhage money. Or -- more precisely -- pools evaporate money. Your therapy pool will never make you one red cent until you get your evaporation problem under control.
- It's much more efficient to keep as much of the water you've already heated (and paid to heat) in the pool than to keep replacing that heat when lost.
- The Department of
Energy has found that water evaporation is overwhelming the single largest
source of energy over consumption, accounting for 70% of total energy lost in
both outdoor and indoor pools.
Take a look at this concrete example of the waste that comes with evaporation:
Take your typical 1,000 square foot pool (let's say 20 x 50
dimension)
A typical indoor pool loses 1-1.5" of water each week to
evaporation
One inch of water lost = 625 gallons of water lost (assuming 1000 sq foot pool)
One gallon of water needs 10 BTU to raise it one degree
It took 62.5 therms of natural gas to heat those 625 gallons
Although it differs state to state and season to season, each therm costs between $1.00-$2.00
You just lost between $62.50-$125 per week (assuming you only
lost 1" of water)
That's can be a loss of $500/month
If your pool is larger -- or if you lost 1.5" instead of 1" of water -- you lost even more.
So what's the answer?
Since evaporation is the chief culprit of both indoor and outdoor pool heat loss, the best way to reduce the effects would be the addition of a thermal blanket.
On an outdoor pool, the use of a thermal blanket translates into an energy savings of 60 - 80 percent.
On an indoor pool, the use of a thermal blanket translates into an energy savings in upwards of 85 percent.
How long would it take for a thermal blanket to "pay for itself"?
Glad you asked! Generally, the payback time is 9 - 18 months.
Need more specifics?
Energy Smart Pools is a program that was written by the U.S. Department of Energy to determine the annual cost savings generated by the use of pool blanket systems.
The software takes into account the surface area of the water, the flow of air across the surface, whether shading is present, the water and room temperature, the size of the pump and ventilation motors, the activity level, the relative humidity and fuel costs to derive the approximate operating cost of the facility.
The system will calculate monthly energy costs and also yields comparison costs for the same pool with a cover. This information is invaluable as it relates to budgeting for a pool blanket system. [Download the DOE software]
Below are some actual examples of the energy savings calculated from actual examples when using pool covers and solar heating options. The assumptions of pool size, water temperature, air temperature, humidity etc. are also provided below.
Projected Pool Heating Costs / Savings
(Keep in mind that the Annual Heating Costs provided in the below chart are for 82 degree pools. Your therapy pool (89-94 degrees) will cost much more to heat -- and subsequently you will save much more with the use of a pool blanket. Also, natural gas costs have more than doubled since this chart was created, from 50 cents/therm to over 1.00/therm. Thus, you will need to more than double the annual heating cost estimate. Better yet, download the DOE software and do the number crunching yourself!).
| City | Pool Type | Annual Heating Costs | Pool Cover Savings | Solar System Savings |
| Atlanta | Indoor | $4,598 | $1,919 | $1,314 |
| Outdoor | $490 | $421 | $417 | |
| Boston | Indoor | $4,695 | $2,028 | $906 |
| Outdoor | $1,389 | $790 | $565 | |
| Chicago | Indoor | $4,698 | $1,996 | $978 |
| Outdoor | $1,042 | $693 | $648 | |
| Dallas | Indoor | $4,468 | $1,881 | $1,641 |
| Outdoor | $250 | $191 | $176 | |
| Denver | Indoor | $4,097 | $1,819 | $1,302 |
| Outdoor | $1,408 | $858 | $730 | |
| Kansas City | Indoor | $4,584 | $1,992 | $1,251 |
| Outdoor | $483 | $393 | $369 | |
| Los Angeles | Indoor | $4,739 | $2,087 | $1,517 |
| Outdoor | $5,827 | $2,615 | $1,512 | |
| Miami | Indoor | $4,038 | $1,549 | $2,023 |
| Outdoor | $2,615 | $1,452 | $1,174 | |
| New York | Indoor | $4,567 | $1,966 | $1,021 |
| Outdoor | $951 | $627 | $582 | |
| Philadelphia | Indoor | $4,567 | $1,966 | $1,021 |
| Outdoor | $951 | $627 | $582 | |
| Phoenix | Indoor | $3,630 | $1,669 | $2,208 |
| Outdoor | $4,094 | $2,011 | $1,402 | |
| Sana Francisco | Indoor | $4,869 | $2,091 | $1,315 |
| Outdoor | $1,826 | $924 | $518 | |
| Seattle | Indoor | $4,743 | $2,034 | $639 |
| Outdoor | $1,756 | $818 | $395 |
Input Variables for Above Examples
| Variable |
Outdoor | Indoor |
| Pool Surface Area | 1000 | 1000 |
| Pool Temperature | 82° | 82° |
| Pool Activity Level | low | low |
| Air Temperature | site specific | 82° |
| Relative Humidity | site specific | 50% |
| Wind Speed at Pool Surface | site specific | still air |
| Annual Operating Dates | May 20-Sep 5* | year around |
| Daily Operating Hours | 9:00am-9:00pm | 9:00am-9:00pm |
| Heating System Efficiency | 75% | 75% |
| Heating Fuel and Cost | Gas $.50/therm | Gas $.50/therm |
| Solar Collector Area | 750 sqft | 750 sqft |
* Except for Los Angeles, Phoenix and Miami which were year around.
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