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In the US, homes with a swimming pool use a whopping 49% more electricity and 19% more gas than homes without one. Yet it’s not the pool itself that’s the main problem.

Energy efficiency company, Opower, examined the energy consumption over four seasons of 2 million homes located in a region with a moderate climate. All homes had gas space-heating and 318,000 had a pool.

At first glance the 49% differential isn’t surprising because pool pumps can use a lot of electricity – 2,000-2,500 kilowatt hours per year. The US has 5.4 million homes with in-ground swimming pools which collectively consume 9-14 billion kilowatt hours running their pools. Opower says:

That’s more electricity than is used each year in 11 individual US states and Washington DC. It’s as if all the retail electricity consumption in New Hampshire could grind to a halt, and then be routed to power the nation’s swimming pools.

Moreover the average home pool in the US holds 76,000 litres. That’s more water than the average human drinks in a lifetime.

But what’s really interesting is the pool itself only accounts for a small part of the higher energy use of pool owners. They also have larger homes on average (by 21%) but that too only accounts for a small part of their higher energy use.

What Opower found is pool owners use more electricity across-the-board:

Our data suggests that pool owners systematically use more energy for reasons beyond their energy-intensive pool pump or their large home size. We found that pool homes use significantly more electricity and natural gas than similarly sized non-pool homes in all 4 seasons, rather than just during the peak-swimming summer months.

One reason is households in pool homes are bigger – they have more children (9% more on average). The primary reason though is pool owners are considerably richer on average than those who own homes without pools.

Their median annual income is double the national median income. Opower notes that higher income implies a greater likelihood of owning “additional TVs, a second refrigerator, and other discretionary appliances.” In other words, higher income households consume more.

There’s a clear parallel here with the Australian Conservation Foundation’s Consumption Atlas, which found a very strong correlation between income and environmental impact:

While high income households spend more on high cost, low impact activities such as entertainment and other services, they also spend more on electricity and most other categories of goods.

Both studies are also another reminder of the key distinction between selection effects and treatment effects. Opower found it’s the characteristics of the population living in homes with pools that’s the key driver of higher energy consumption, not the fact of the pool itself.

Similarly, the ACF found that inner city households in Australia – which on average have high incomes – have a considerably higher environmental impact than households located elsewhere. That’s despite having the advantages of higher density, better public transport and proximity to jobs. According to the ACF, the population characteristics “overwhelm” the physical attributes of the location.

The implication isn’t that the decision of higher income households to have a pool or not, or to live in the inner city or not, doesn’t matter for the environment. Rather, it’s that planning and design is only part of the solution. Perhaps we focus on it because it’s more tractable (and for higher income groups is possibly least painful), but it’s not the only game in town.

As the ACF suggests, we should recognise that urban policies are only one way of encouraging much-needed changes in human behaviour toward greater sustainability.

Meanwhile, home owners with a pool have many options for reducing electricity consumption. One is using their pool as a heat exchanger for the central refrigerated air con system!