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Solar heating options for above-ground pools

Above-Ground Pool Heating Reference Chart for Dome-Style Solar Heaters

Pool Volume Days Required to Heat Pool Five Degrees
Pool Dimensions Litres (Gallons) Typical 0.4 m2 (4 sf) Dome Typical 0.8 m2 (9 sf) Dome
3.6 m x 0.9 m (12 ft x 36 in.) 7,896 L (2,086 gal) 2.5 1.2
4.5 x 1.2 m (15 ft x 48 in.) 16,807 L (4,440 gal) 5.3 2.6
5.5 x 1.3 m (18 ft x 52 in.) 26,426 L (6,981gal) 8.3 4.2
7.3 x 3.6 x 0.6 m (24 x 12 x 2 ft) 29,094 L (7,686 gal) 9.1 4.6
6.4 x 1.3 m (21 ft x 52 in.) 35,015 L (9,250 gal) 11 5.5
7.3 x 1.3 m (24 ft x 52 in.) 47,246 L (12,481 gal) 14.9 7.4
9.7 x 4.8 x 1.3 m (32 x 16 ft x 52 in.) 54,373 L (14,364 gal) 17.1 8.5
9.1 x 1.3 m (30 ft x 52 in.) 71,525 L (18,895 gal) 22.5 11.2
12.5 x 5.5 m (41 x 18 ft) 102,206 L (27,000 gal) 32.1 16.1
This chart shows typical average water temperature increase for dome-style heaters. Other styles may have slightly varied results, but still only provide gradual heating. Chart courtesy GAME.

Pool heating hybrid

Heat pump pool heating technology is essentially a hybrid of passive and active heating. These systems transfer heat energy from the air to heat the water as it passes through the unit, making them more economical to operate than gas heaters. They do not generate heat directly; rather, they harness and repurpose it.

According to the U.S. Department of Energy (DOE), heat pumps are an energy-efficient way to heat a swimming pool. As the pool’s pump circulates water for filtration purposes, it also passes water through the pump’s heater. The heater has a fan drawing in outside air and directing it over an evaporator coil. Liquid refrigerant within the evaporator coil absorbs the heat from the outside air and as its temperature increases, it converts into a gas. The warm gas inside the coil then passes through a compressor. The compressor increases the heat and the gas becomes very hot as it passes through the condenser, which then transfers the heat from the hot gas to the cooler pool water as it passes through on its way back to the pool. Meanwhile, the hot gas reverts back into liquid and returns to the evaporator so the process can repeat. A heat pump heater is essentially an air-conditioner in reverse.

The DOE’s guide to energy efficiency and renewable energy states heat pump pool heaters perform efficiently when the air temperature is at least 7 C (44.6 F), which is a lot cooler than most people would consider to be outdoor swimming weather. The warmer the outside air, the less energy a heat pump heater requires to warm the water. So during the swimming season, such a unit can be very efficient.

According to the DOE, heat pump pool heaters generally cost more up front than gas heaters, but their annual operating costs are dramatically lower and they tend to last longer.

As efficient as they are, however, heat pumps cannot beat solar pool heating on the score of energy consumption for pool heating. Solar heating systems use only the energy required to move the water from the heat source to the pool.

● When adding top-off water to the pool, position the hose to sit in the sun for a while, allowing the fill water to warm up prior to adding it to the pool.
● Minimize the distance water has to travel between the heat source and the pool. Pumping water over large distances increases both installation and energy costs of running the pump.
● Cover the pool when not in use to conserve heat and water.

Combined efforts

The most effective pool heating systems combine heat collection (or active generation) with retention. In other words, no matter how heat is added to the pool water, retaining as much of it as possible by covering the pool when it’s not in use is critical if the goal is energy-conscious pool heating. This is akin to keeping doors and windows closed when the air-conditioner (or, more similarly, the furnace) is on.

Like many things, making a pool heating decision comes down to common sense. Customers need to understand what they want to accomplish, and pool professionals need to know what combination of products get the job done. When the desired outcome is an environmentally friendly, cost-effective way to increase pool water temperature by a few degrees, solar-technology is extremely efficient.


Smith_HeadshotMitch Smith is vice-president, specialty channel sales for GAME, a swimming pool and accessories manufacturer in Scottsdale, Ariz. He has been in the pool and spa industry for almost 30 years, having worked with Muskin, Zodiac and Vogue prior to joining GAME. Smith can be reached via e-mail at


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