In most countries electricity use is rising. The increase is gradual in developed areas, averaging only 1 or 2% a year. In the UK, the pattern was similar but recent years have tended to show declining growth rates, partly perhaps as a result of increasing prices. One of the most interesting features of recent UK trends has been the flattening in electricity use in the home. This change is somewhat surprising. Improvements in home energy efficiency, through such things as the use of compact fluorescent light bulbs and high quality white goods, have usually been thought to have been outweighed by increases in the number and power use of consumer electronics. Large LCD TVs are, for example, much heavier electricity users than the old-fashioned TVs that they replace. Today’s games consoles are much more powerful than ones of five years ago.

So the reasons are not clear, but monthly year-on-year growth in domestic consumption of electricity has fallen to below zero in the last year or so. Is this a temporary change brought about by the steep increases in prices over the period 2005-6, which will be unwound when people get habituated to higher costs? Or is this a real change in household behaviour?

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First of all, let’s look at the trend over the past few years:

Domestic consumption

Electricity use rose from just over 98 TWh in 1998 to about 110 TWh in 2006, rising at an average of over 1.3% per annum. The last four years of this period saw a much slower rise of about 0.8% a year.

If we look at the quarterly data over the last two years, the slowdown is even clearer:[*]

Quarterly domestic electricity consumption

There is a strong seasonal pattern in electricity sales to households. Winter consumption is much higher than summer. But almost all quarters are lower than the figure of a year before. Please note that some UK homes are heated by electricity and so overall winter consumption partly depends on temperatures. Summer consumption is an easier guide to long run trends. Summer 2007 was marginally higher than summer 2006 but lower than summer 2005. We can be fairly confident that the quarterly data shows consumption growth trailing off.

The position is even clearer when one looks at monthly year-on-year trends:

Trailing 12-month rolling average

For over a year, rolling average home electricity consumption has been falling. Granted, since the middle of last summer the line has been creeping up towards the 0% level but the year to November 2007 was still over 2% lower than the previous year to November.

The evidence is strong that domestic electricity use is beginning to stabilise.

Why is this? Is it a response to the high prices of 2005-6? Did the slight fall in prices in 2007 cause the slight uptick in the second half of that year? It will be some time before we know, but this is one of the first indications that government energy efficiency policies are beginning to work.

Lower rates of growth in electricity consumption don’t feed necessarily into reduced carbon emissions. It depends crucially on the fuel mix in the power stations. Coal has been the largest source of power over the last few years, but as many of the coal plants enter the period of restricted annual working hours, there is likely to be a slow switch back to gas. And most of the new capacity planned is gas turbines. This will be good for emissions.

Domestic use is 30% of all electricity consumption, and a higher fraction at times of peak demand. If the trend identified in this note is a real behaviour change, it will be good news both for carbon emissions and for those concerned about whether the UK will have enough peak capacity in the latter half of the next decade.

(All figures in this note are from the magisterial Digest of UK Energy Statistics, published by BERR, usually known as DUKES.)

Footnote [*] Graph updated on Tuesday 17 February 2009 to correct an error with the scale of the y-axis. Thanks to Garth Higginbotham for drawing this to my attention.