Since swimming pools are used on bright sunny days, it's natural to turn to the sun to keep the water clear. Installing solar panels to run your pool pump is not only an investment that can pay you back many times over, but a way to reduce your carbon footprint and environmental impact.
The water in a family swimming pool must be completely filtered, or "turned over," once every 24 hours. This makes an intermittent power source, such as solar, a good source for the pump since it doesn't need to run continuously. The California Swimming Pool Energy Conservation Task Force suggests as little as four hours of filtering during summer months and two hours of filtering over the winter. Of course, heavier use may require more filtering to keep your water clear, but minimizing the amount of filtration translates into decreased investment in solar panels.
To get started, calculate your turnover time. Ask your builder or estimate the volume of your swimming pool in gallons. Then find the flow rate of your system in gallons per minute, which is determined by the size of your pool's filter. Use the average flow rate marked on your filter. Divide the volume of the pool by the flow rate to determine the approximate number of minutes it will take to turn your pool over. This is the minimum amount of time your pump will need to operate each day.
Putting the System Together
Most pool pumps are rated between one and two horsepower and will draw about 800 watts of energy per horsepower for each hour of operation. The largest commercially available solar panels provide 200 watts of electricity an hour, so a one horsepower pump would require four panels to operate. In a very sunny climate, hooking these panels to an inverter connected directly to your pump may be all you need to do.
In most regions, however, the sun doesn't always shine, so you'll need a way to filter your pool at night or on cloudy days. A bank of batteries can store electricity for when it's needed, but storage batteries can be expensive to install and require replacement every few years. For most users, a grid tie solar inverter is a better solution. This device draws power from the electrical grid when needed and "sells" excess solar power back to the electric company when your pool isn't operating.
The initial cost of a grid tie system is comparable to a battery storage system, but it enables you to add more solar panels to power additional appliances in your home or recoup your investment by selling power. Many states offer incentives or tax breaks to reduce the installation costs of your solar system.