Pool full of Coal

Winter is a tough time to hold down electricity consumption. Days are shorter so lights burn longer. The cold air begs for hot tea, hot meals, hot water, and hot electric heaters. (See this post on heaters.) Even solar-heated water needs an electric boost in the winter. But there is one easy place to save electricity as the days get colder: the swimming pool.

One of the best things anyone can do to make a greener house is to fill in the pool. Swimming pools waste water, use huge amounts of electricity, and require toxic chemicals. But my kids would kill me if I filled in the pool, and there are ways to mitigate the environmental cost of a pool.

The first priority is to get a pool cover that keeps out dirt and ultraviolet and prevents evaporation. If it’s a bubble cover, it will keep your pool warmer, too. In Namibia the law insists on pool covers to prevent evaporation. A cover will save thousands of litres a year.

Ultraviolet breaks down chlorine, which is why you have to add cyanuric acid to stabilize the chlorine. Put on a pool cover and you can save on both stabilizer and chlorine. Most important, with less dirt and more effective chlorine, you should be able to reduce your pool pump’s running time.

In most homes with a pool, the pump is the second or third largest consumer of electricity, after the geyser. If I followed HTH’s standard recommendation to run my pool pump 12 hours a day in the summer, and if I hadn’t resisted a sales pitch a couple of years ago to trade in my 750 watt pump for a new 1 100 watt model, I would be using 13 kilowatt hours a day to filter pool water, more than half my current total daily consumption.

Ignore HTH’s 12-hour guideline, and rather follow the suggestions of the California Swimming Pool Industry Energy Conservation Task Force:

Reduce filter operating times to no less than 4 to 5 hours per day during the summer and 2 to 3 hours per day during the winter period. This will reduce annual electrical consumption by 40 to 50 percent. Normal and heavier swimming use may require as much as eight or more hours filtration per day. Should water clarity or chemical imbalance indicate inadequate filtration, immediately operate the filter until acceptable water clarity has again been established. If additional filtration is still indicated, increase filter operating time in one-half hour increments until the water remains clear and properly balanced chemically.

I run my pool six or seven hours a day during the summer. Since cold water inhibits the growth of nasties, yesterday I reset the pump timer to three hours for the winter. Eskom struggles to keep up with peak winter demand in the morning between 6 and 10 a.m. and in the early evenings between 6 and 9 p.m., so make sure the timer is not set to run the pump during those hours.

All of this inspired me to do some calculations. A cubic metre of coal can produce roughly 3 000 kWh of electricity. My pool holds roughly 30 cubic metres. So if I kept a 1.1 kw pump running 12 hours a day year-round, as many South Africans do, the coal burned over 18 years to keep that pump going could fill the pool to the brim. Better a green pool than a black one.