Saturday, 17 December 2011

The Jevons paradox

Coming back from Malvern last evening, I was struck more than usually by the degree to which people seem to have money (and carbon) to burn. Above is a detail from a photograph I took on a bright Summer day in a tent at Cheltenham Racecourse - Greenbelt: they should know better. Now, as Christmas approaches, I noted once again that there is hardly a house without its tree lit up, visible through the unclosed curtains. Worse still is the number of houses with flashing lights festooned over their exterior.

And, yes, the roofs of some of those houses even sport photovoltaic panels. Thus supporting the theory of W.S. Jevons, writing some 170 years ago: Jevons argued that improvements in fuel efficiency tend to increase, rather than decrease, fuel use: he observed that England's consumption of coal soared after James Watt introduced his coal-fired steam engine, greatly improving on the efficiency of earlier designs. Watt's innovations made coal a more cost-effective power source, leading to the increased use of the steam engine in a wide range of industries. This in turn increased total coal consumption, even as the amount of coal required for any particular application fell. At that time, many worried that coal reserves were dwindling: some thought increasing efficiency would reduce consumption. Jevons however argued that further increases in efficiency would tend to increase the use of coal. Hence, increasing efficiency would tend to increase, rather than reduce, the rate at which England's coal deposits were being depleted.

Similarly, those benefiting from the feed-in tarrif are saying, perhaps: "What the heck? Now we don't need to worry about turning the lights off!" What prospect therefore of fossil fuels being left in the ground?

1 comment:

Fr. Peter Doodes said...

This is one of those obvious principles that have been so obvious that I have overlooked it.

If I ran a car 25 years ago that did 33 mpg and now run a car that did 66 mpg then the fact that petrol has doubled in price over that period is irrelevant, in fact since my car is so much more economical my mileage has increased...

Much the same goes for my energy saving lights, where I would turn off all lights prior to them my concerns now have lessened.

Thank you for this timely reminder Martin!