White LED lies: It's great, but Nobel physics prize-winning great?

How artificial lighting could offer an artificial promise

Light up my world

That LEDs use less power to produce more lumens is true. But that doesn't actually mean that people will then use these new bulbs to consume less electricity. For what we don't actually know is the electrical price of lumens? How much will our behaviour change, and how much will our desire to light up our surroundings change when the price alters? This is, of course, the province of dismal science, not of physicists. Which might be why a committee of physicists didn't consider this point. Although one of the potential picks (he's been on everyone's long list for years) for Monday's economics prize has looked at this. I refer of course to William Nordhaus (PDF).

Other work, building on his historical examination of the price of artificial light, has looked at the consumption of artificial light (PDF) with respect to price. The answer seems to be that we humans really rather like artificial light. So much so that we're prepared to spend 0.7 per cent of our income on it. A number that has held static over centuries.

When light gets cheaper then we just have more of it. Which, of course, means that if light gets cheaper then we might just have ever more of it, as opposed to not using the energy and having the same amount we do now.

Some will recognise this as a version of Jevon's Paradox: as the energy derived from coal becomes cheaper as a result of technical advances then what happens to the demand for coal? It's possible (only possible) that demand for coal will rise as the cheapness of the energy increases our lust for energy more than the new efficiency of the process reduces it.

We're also pretty sure that such elasticities, while they can go in any direction over quite long time scales, don't stay that way. Think of the demand for water: we'll all pay just about anything for the couple of litres a day that will keep us alive. We're willing to pay rather less for the amount needed for that second bath of the day: and when the mains burst and the basement fills up, we'll pay good money for people to make it go away. We don't really know where we are with lighting.

We can look at history and see that it's (or at least appears to be) pretty much a straight line, 0.7 per cent of income. When incomes rise we use more light if light stays the same price. If the price of light drops then we'll have more light (thank you), up to that same portion of income. And yes, we do also note that there are times when we'll pay to have light taken away: this is known as “a curtain”. But when is the inflexion point? When will we be satiated with light and thus energy efficiency, in its provision, will lead to less energy use? As this climate change policy blog puts it:

There seem to be at least three good reasons for suggesting that demand for lighting services will continue to grow strongly in the coming decades. First, interior light levels are still well below the intensity of daylight, by as much as one or two orders of magnitude.  There is no immediately apparent reason why people should have an intrinsic preference for lower light levels than found naturally, at least for much of the time, and especially in winter.

Second, every major technological shift has caused an increase in the consumption of lighting services. LED lighting now appears, together with other technologies, to be introducing such a major technological shift. There will surely be significant progress in the coming decades, with costs falling and the quality of the light improving.

If the historical pattern is followed this will lead to an increase in demand.

Third, incomes will continue to rise, which is also likely to lead to an increase in demand.

The exciting answer here is, well, we dunno. We're just going to have to suck it and see. Which is the answer to many thorny questions that people try to answer using the imperfect tools of economics. We really only know two things about the demand for light. Historically, when the price falls, we just use more of it.

Secondly, at some point, we expect satiation and thus increasing efficiency to lead to reduced energy consumption. But we don't know when that will be: and our suspicion, at the very least, is that it ain't yet.

I'd also point to the fact that it has already changed the world quite a lot, whatever happens to lighting, or how we use light. But, given that we don't actually know what our reaction will be to falling real prices for artificial lighting, then it's too early to tell whether LEDs are going to lead to reduced electricity consumption. It might just turn out to be a brighter world instead. ®

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