Knowledge Problem

Michael Giberson

The current issue of The Economist reports on research that concluded “making lighting more efficient could increase energy use, not decrease it.”

SOLID-STATE lighting, the latest idea to brighten up the world while saving the planet, promises illumination for a fraction of the energy used by incandescent or fluorescent bulbs. A win all round, then: lower electricity bills and (since lighting consumes 6.5% of the world’s energy supply) less climate-changing carbon dioxide belching from power stations.

Well, no. Not if history is any guide. Solid-state lamps … will indeed make lighting better. But precedent suggests that this will serve merely to increase the demand for light. The consequence may not be just more light for the same amount of energy, but an actual increase in energy consumption, rather than the decrease hoped for by those promoting new forms of lighting.

Lighting efficiency is just the latest in a long line of examples of the Jevons Paradox – the observation made in 1865 by William Stanley Jevons that increasing the efficiency with which a fuel is used may increase the overall consumption of the fuel. (Also sometimes called “the rebound effect.”)  Jevons observed that improvements in the efficiency of coal use led to increases in coal consumption.

Conservationists and environmentalists sometimes complain about the Jevons Paradox, note the defensive tone from Energy Circle, “The Jevons Paradox: Time to Send it The Way of the Dodo?,” or The Encyclopedia of Earth entry on the paradox. But is isn’t the case that the lower-cost based rebound is always so big as to overwhelm efficiency-based savings.  The key issue, Edward Glaeser reminds us in a recent column, is “that the demand for the thing in question (power, vehicle miles, tasty cookies, cigarettes) has to be sufficiently elastic with respect to the thing’s price.”

The Economist‘s story draws on an article recently published in the Journal of Physics D: Applied Physics by Jeff Tsao and co-authors, “Solid-state lighting: an energy-economics perspective.”  The magazine sums up the piece as concluding that new, highly efficient solid-state lighting could increase the consumption of light by ten times over the next 20 years, and even though those lights will be more efficient, energy consumption for lighting would double (if the real price of electricity remains stable).  That would make for a pretty big rebound.

NOTE: There is much more detail on the assumptions and calculations that went into the conclusion reported in The Economist. Related research is available from Sandia National Lab. Here’s the full abstract of the Tsao, et al. article:

Abstract: Artificial light has long been a significant factor contributing to the quality and productivity of human life. As a consequence, we are willing to use huge amounts of energy to produce it. Solid-state lighting (SSL) is an emerging technology that promises performance features and efficiencies well beyond those of traditional artificial lighting, accompanied by potentially massive shifts in (a) the consumption of light, (b) the human productivity and energy use associated with that consumption and (c) the semiconductor chip area inventory and turnover required to support that consumption. In this paper, we provide estimates of the baseline magnitudes of these shifts using simple extrapolations of past behaviour into the future. For past behaviour, we use recent studies of historical and contemporary consumption patterns analysed within a simple energy-economics framework (a Cobb–Douglas production function and profit maximization). For extrapolations into the future, we use recent reviews of believed-achievable long-term performance targets for SSL.We also discuss ways in which the actual magnitudes could differ from the baseline magnitudes of these shifts. These include: changes in human societal demand for light; possible demand for features beyond lumens; and guidelines and regulations aimed at economizing on consumption of light and associated energy.