DECC numbers on energy efficiency need checking

Today’s presentation on electricity efficiency opportunities from the Department of Energy (DECC) makes a series of important errors in its estimates of the savings that can be made in domestic homes.[1] For example DECC overstates the amount of power used in domestic lighting by almost a factor of three. Its projected efficiency savings are almost twice as great as today’s total use of electricity for this purpose. By contrast, DECC substantially underestimates the use of power for space and water heating. What is most surprising is the clear conflict between many of the figures presented and other recently published DECC data. Today’s document was supposed to show the large possibilities for improvements in the efficiency of electricity use. What seem to be simple mistakes completely undermine its credibility. More fact checking, please. Domestic homes consume about a third of all UK electricity. This figure is tending to rise both because of de-industrialisation and because of the relatively slow progress at reducing electricity use in households. It is only recently that home use has fallen substantially whereas industrial and commercial consumption has been falling for most of the last decade.

Efficiency matters. As DECC said on its web site when it released the presentation today.

Encouraging greater efficiency in the use of electricity is potentially very valuable to all of us. It can reduce electricity bills both directly and also indirectly through limiting the overall cost of the electricity system in terms of funding for new generation, transmission and distribution infrastructure.


This DECC report suggest that domestic homes use 42 terawatt hours (TWh, over 10% of total UK electricity demand). In the magisterial GB Housing Energy Fact File, published by DECC in September 2011, this figure is estimated at only 16.5 TWh.[2] This second figure is widely used and is assumed to be approximately accurate. The recent Energy Savings Trust report suggests an even lower figure of about 540 kWh a year per house, equivalent to about 14 TWh for all UK homes.

Today’s  DECC document estimates that efficiency savings of 26 TWh can be made, largely by the replacement of old-fashioned light bulbs (‘incandescents’) by compact fluorescent lamps(CFLs). So the total savings claimed to be available are far greater than total domestic use. Not only is the number wrong, but the efficiency improvements from the switch to CFLs have already been partly made. The remaining gain will come from moving from comparatively wasteful CFLs to high efficiency LEDs. The savings from this switch might be about 10 TWh but are unlikely to be more.

Appliances and electronics

The new DECC document says that appliances and electronics in homes consume about 47 TWh but its own September 2011 report suggested a figure of 58.4 TWH, a figure almost 25% higher and in rough agreement with the EST June analysis.

In the case of home electronics, efficiency savings of 38% are said to come from a reduction in standby losses. (I could find no source provided for this estimate).This is not a credible figure. No modern consumer electronics now have significant power consumption when not in use and efficiency saving will be much lower than 38%

Heating use

The new report suggests that household electricity use can be reduced by building improvements such as installing ‘high efficiency windows’. The total potential saving identified is almost 15 TWh. But in another DECC document, this time from 2010, the total amount of electricity used to heat UK homes is estimated at 17 TWh.[3] Therefore the new estimate is that almost 90% of electricity consumption to heat homes can be avoided by retrofitting insulation and other improvements. This is not a supportable assumption.


Reducing electricity demand in the UK is an important objective. I have only researched the section on domestic use but this portion is said to offer almost half the possible efficiency savings.  Furthermore, the costs of efficiency improvements are stated to be less than the financial gains to the householder from using electricity. This assumption, which in my experience is rarely true, is never examined. It seems to me that the DECC report does not meet reasonable expectations for policy proposals from a government department, even in the draft form in which it is currently presented.