Americans tend to use more and more of everything. As incomes have risen, we buy more food, live in larger homes, travel more, spend more on health care and, yes, use more energy. Between 1950 and 2010, U.S. residential electricity consumption per capita increased 10-fold, an annual increase of 4 percent per year.
But that electricity trend has changed recently. American households use less electricity than they did five years ago. The figure below plots U.S. residential electricity consumption per capita 1990-2015. Consumption dipped significantly in 2012 and has remained flat, even as the economy has improved considerably.
Source: Constructed by Lucas Davis at UC Berkeley using residential electricity consumption from EIA, and population statistics from the U.S. Census Bureau.
The decrease has been experienced broadly, in virtually all U.S. states. The figure below shows that between 2010 and 2015, per capita residential electricity consumption declined in 48 out of 50 states. Only Rhode Island, Maine and the District of Columbia experienced increases.
Source: Constructed by Lucas Davis at UC Berkeley using residential electricity consumption from EIA, and population statistics from the U.S. Census Bureau. Electricity use per capita is measured in megawatt hours.
This pattern stands in sharp contrast to previous decades. During the 1990s and 2000s, for example, residential electricity consumption per capita increased by 12 percent and 11 percent, respectively, with increases in almost all states. Previous decades experienced much larger increases.
So what is different? Energy-efficient lighting. Over 450 million LEDs have been installed to date in the United States, up from less than half a million in 2009, and nearly 70 percent of Americans have purchased at least one LED bulb. Compact fluorescent lightbulbs (CFLs) are even more common, with 70+ percent of households owning some CFLs. All told, energy-efficient lighting now accounts for 80 percent of all U.S. lighting sales.
It is no surprise that LEDs have become so popular. LED prices have fallen 94 percent since 2008, and a 60-watt equivalent LED lightbulb can now be purchased for about $2. LEDs use 85 percent less electricity than incandescent bulbs, are much more durable and work in a wide-range of indoor and outdoor settings.
Source: Energy.Gov, “Revolution…Now”, September 2016.
Is this really big enough to matter? Yes! Suppose that between LEDs and CFLs there are now one billion energy-efficient lightbulbs installed in U.S. homes. If operated 3 hours per day, this implies savings of 50 million megawatt hours per year, or 0.16 megawatt hours per capita, about the size of the decrease above. Thus, a simple back-of-the-envelope bottom-up calculation yields a similar decrease to the decline visible in aggregate data.
No other household technology is as disruptive as lighting. Incandescent bulbs don’t last long, so the installed stock turns over quickly. Air conditioners, refrigerators, dishwashers and other appliances, in contrast, all have 10+ year lifetimes. Thus, although these other technologies have also become more energy-efficient, this can’t explain the aggregate decrease. The turnover is too slow, and the gains in energy-efficiency for these other appliances have been too gradual for these changes to explain the aggregate pattern.
Traditional economic factors like income and prices also can’t explain the decrease in electricity use. Household incomes have increased during this period, so if anything, income effects would have led electricity use to go up. Moreover, between 2010 and 2015, the average U.S. residential electricity price was virtually unchanged in real terms, so the pattern does not seem to be the result of prices.
Another potential explanation is weather. The summer of 2010 was unusually hot, so this partly explains why electricity consumption was so high in that year. But the broader pattern in the figure above is clear even if one ignores 2010 completely. Moreover, I’ve looked at these data more closely and there is a negative trend in all four seasons of the year: summer, fall, winter and spring.
This is not the first time in history that lighting has experienced a significant increase in energy-efficiency. In one of my all-time favorite papers, economist Bill Nordhaus examines the history of light from open fires, to candles, to petroleum lamps, to electric lighting. Early incandescent lightbulbs circa 1900 were terribly inefficient compared to modern incandescent bulbs, but marked a 10-fold increase in lumens per watt compared to petroleum lamps. However, as lighting has become cheaper, humans have increased their consumption massively, consuming thousands of times more lumens than they did in the past.
Economists refer to this price effect as the “rebound effect”. As lighting becomes more energy-efficient, this reduces the “price” of lighting, leading to increased consumption. An important unanswered question about LEDs is to what extent will these energy efficiency gains be offset by increased usage? Will households install more lighting now that the price per lumen has decreased? Will households leave their lights on more hours a day? Outdoor lighting, in particular, would seem particularly ripe for price-induced increases in consumption. These behavioral changes may take many years to manifest, as homeowners retrofit their outdoor areas to include additional lighting.
It is not clear yet whether U.S. household electricity use has indeed peaked or this is just a temporary reprieve. Probably the biggest unknown in near future is electric vehicles. Currently only a small fraction of vehicles are EVs, but widespread adoption would significantly increase electricity demand. It is worth highlighting, though, that this would be substitution away from a different energy source (petroleum), so the implications are very different from most other energy services.
Over a longer time horizon there will also be entirely new energy-using services that come available, including services that are not yet even imagined. The 10-fold increase in electricity consumption since 1950 reflects, to a large degree, that U.S. households now use electricity for many more things than they did in the past. The recent decrease is historic and significant, but over the long-run it would be a mistake to bet against our ability to consume more energy.