Maintaining a pool isn't cheap. AquaCal, a pool pump manufacturer, reports that heat pumps cost between $50 and $150 a month for pool owners. However, taking a few steps can drastically reduce the cost it takes to heat your in-ground pool.
Use a Pool Cover
The U.S. Department of Energy asserts that covering a pool when it's not in use is the single most effective way to reduce pool heating costs. The agency estimates that covering a pool saves between 50 and 70 percent in heating costs. Pool covers can reduce costs by minimizing evaporation, which is the primary way that pools lose heat and energy. At the time of publication, full-sized pool covers start at $40 at retailers like Home Depot and Walmart.
Although pool covers do a great job of keeping heat in your pool, they also decrease the amount of energy your pool gets from the sun's rays. To minimize this effect, go for a transparent bubble cover or solar cover rather than an opaque one. According to the Department of Energy, transparent covers only reduce solar energy absorption by 5 to 15 percent while you can lose 20 to 40 percent with an opaque cover.
Use a Solar Pool Heater
Rather than purchasing a gas heater or a heat pump for your pool, try a solar pool heater instead. The Department of Energy notes that the cost of a solar pool heater -- about $3,000 to $4,000 including installation costs -- is comparable to gas heaters and heat pumps. Once purchased, though, solar pool heaters have extremely low monthly costs. Because they harness the sun's energy, a solar pool heater won't drive up your gas or electric bill.
A solar pool heating system typically includes a solar collector, a filter, a pump and a flow control valve. The agency notes that a properly maintained solar pool system should last between 10 and 20 years.
A low [pool temperature](http://energy.gov/energysaver/articles/managing-swimming-pool-temperature-energy-efficiency) means a lower energy bill. Reduce the temperature to 78 degrees, and turn the heat off if the pool won't be used for several days.
Optimize Your Pool Pump
Whether you have a solar pool heater or a heat pump system, using the right pump in the right way can save money. The Department of Energy notes that a large pump increases energy and maintenance costs, so it's important to use the smallest pump necessary for your size pool. The agency notes that a 0.75 horsepower pump is sufficient for most residential pools, but check your pool supplier's design chart for exact information.
Along with downsizing your pump, don't run your pump any longer than necessary. The Department of Energy recommends keeping the pump on for 3 to 6 hours per day. If you still have debris in your pool, use a skimmer or a vacuum rather than turning on the pump. Take extra care to keep the intake grates clear and use a timer to keep the pump from running too long. Your efforts will be worth it -- the department reported that pool owners who replaced their pump and reduced pump time saved an average of 75 percent on energy costs.