Question: What do the following homes have in common?
Answer: All of these green homes have swimming pools. That shouldn’t come as a big surprise, since residential swimming pools are increasingly common in North America. Back in 1950, there were only 2,500 private residential pools in the U.S.; now there are over 7 million of them.
Although residential pools no longer raise eyebrows, they nevertheless deserve the scrutiny of the green building community. Let’s be frank: swimming pools are energy and water hogs.
In homes with swimming pools, more energy is used to run the pool pump than anything else except the heating system and air conditioner. In fact, the typical California pool uses enough electricity during the summer season to power the average home for three months.
One study that looked at pool-pump energy use was conducted by Danny Parker, a senior researcher at the Florida Solar Energy Center. Parker monitored energy use at 204 Florida homes, 24% of which had swimming pools. On average, the pool pumps used 4,200 kWh per year. (For comparison, the average monitored home used 5,695 kWh per year for air conditioning and 2,227 kWh for water heating.)
According to one source, homes with swimming pools use 58% more water than homes without pools. Another source reports that pool-equipped homes use twice as much water for outdoor uses as pool-free homes.
The typical backyard swimming pool holds 16,000 to 20,000 gallons of water. Pool evaporation amounts to 3 to 7 feet of water per year. For a 15 by 30 foot pool, the range is 10,000 to 23,000 gallons per year for evaporation, plus about 25% to account for splashing. If the pool is filled once a year, it requires about 38,000 gallons of water every year.
Residential water use varies from state to state, ranging from about 60 to 110 gallons per person per day — equal to 21,900…