A recent story in The Wall Street Journal (subscription required) reminds us of the difficulty in trying to reduce energy consumption. The story, by Jo Craven McGinty, notes that after 3 decades of effort aimed at lowering residential energy use in the United States, the overall level of consumption is still about the same, about 10 quadrillion BTUs per year.
Taking a deeper look, however, there is some positive news in the data. While overall consumption is nearly unchanged, the average energy consumption per household has decreased, dropping to about 90 million BTUs a year in 2009 (latest year available) from about 114 million BTUs in 1980.
So, what is going on? Several things: newer homes tend to be larger than older ones. And though they have more efficient envelopes and systems (double-pane windows, improved insulation, and efficient heating-cooling systems), it takes more energy to heat larger spaces, and the proliferation of devices in homes has required more energy use. We now plug in more TVs, computers, DVRs, mobile phones, and second refrigerators.
The Efficiency Paradox
While our homes are more efficient, this is offset by an increase in energy consumption, a phenomenon called the rebound effect, or the Jevons Paradox, which holds that an increase in efficient use of a resource, like energy, can result in greater use and reduce the benefit. This is not a hard and fast rule, and it is often debated among economists. Nonetheless, there is a propensity toward squandering some efficiency gains once realized. For example, when gas prices drop significantly, the cost per mile is lower, and people are more inclined to drive further or faster.
As McGinty points out, Americans receive mixed messages, being hectored to conserve energy while also being constantly invited to buy new gadgets and appliances that require energy. This is evident in the U.S. Energy Information Administration data showing how consumption by type has changed. In 1993, appliances, lighting, and electronics accounted for 24% of home consumption, which rose in 2009 to 34.6%. Space heating was 53% of home energy consumption in 1993 and decreased to 41.5% in 2009.
Annual Residential Energy Consumption by End Use, U.S.: 2009
(Source: U.S. Energy Information Administration)
Helping to reduce residential consumption lies at the heart of home energy management systems and represents a key goal of utility energy efficiency programs. No one is suggesting these efforts should stop just because the net result can seem frustratingly ineffective, or merely incremental. But, as noted in Navigant Research’s report, Home Energy Management, one of the inhibitors to wider adoption is the uncertainty around net benefits. Some argue that one way to avoid the rebound effect would be a tax to keep the cost of energy use the same. But that would be a hard sell.
Tags: Building Systems, Energy Management, Home Energy Management, Utility Transformations
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