Unintended consequences

The Economist describes a study indicating that efforts to control energy use — and thus reduce its expense — by mandating more efficient sources of artificial light may well have the opposite effect.

.... The light perceived by the human eye is measured in units called lumen-hours. This is about the amount produced by burning a candle for an hour. In 1700 a typical Briton consumed 580 lumen-hours in the course of a year, from candles, wood and oil. Today, burning electric lights, he uses about 46 megalumen-hours—almost 100,000 times as much. Better technology has stimulated demand, resulting in more energy being purchased for conversion into light. ....

.... Assuming that, by 2030, solid-state lights will be about three times more efficient than fluorescent ones and that the price of electricity stays the same in real terms, the number of megalumen-hours consumed by the average person will, according to their model, rise tenfold, from 20 to 202. The amount of electricity needed to generate that light would more than double. Only if the price of electricity were to triple would the amount of electricity used to generate light start to fall by 2030.

Dr Tsao and his colleagues see no immediate end to this process by which improvements in the supply of light stimulate the desire for more—rather as the construction of that other environmental bête noire, roads, stimulates the growth of traffic. Even now, the interiors of homes and workplaces are typically lit at only a tenth of the brightness of the outdoors on an overcast day, so there is plenty of room for improvement. And many outdoor areas that people would prefer to be bright at night remain dark because of the expense. If money were no object, some parts of the outdoors might be illuminated at night to be as bright as day.

It is worth remembering that when gas lights replaced candles and oil lamps in the 19th century, some newspapers reported that they were “glaring” and “dazzling white”. In fact, a gas jet of the time gave off about as much light as a 25 watt incandescent bulb does today. To modern eyes, that is well on the dim side. So, for those who truly wish to reduce the amount of energy expended on lighting the answer may not be to ban old-fashioned incandescent bulbs, as is the current trend, but to make them compulsory. [more]

Energy conservation: Not such a bright idea | The Economist