The expected electricity plant margin for winter 2006-07 as published in national grid's winter report
http://www.ofgem.gov.uk/temp/ofgem/cache/cmsattach/16803_168_06.pdf
is 22 per cent.
The best assessment of the expected electricity plant margin over the years 2007 out to 2013 is illustrated in the following table, taken from national grid's Seven Year Statement of May 2006
http://www.nationalgrid.com/uk/Electricity/SYS/current/.
This gives projections against three generation scenarios, reflecting the extent to which proposed new transmission contracted plant does, in the event, proceed to completion, provided both by customers and national grid itself.
Percentage plant margin (SYS1 update, May 2006) 2006-07 2007-08 2008-09 2009-10 2010-11 2011-12 2012-13 Customer based—SYS1 21.3 22.6 33.0 35.6 43.6 46.6 46.2 Customer based—C2 21.3 20.1 21.5 20.1 17.1 15.9 14.5 Customer based—E,UC3 21.3 18.3 18.2 16.7 13.9 12.7 11.3 NGET base—SYS1 22.6 25.7 37.1 40.3 49.2 52.8 53.0 NGET base—C2 22.6 23.2 25.2 24.2 21.7 20.8 19.8 NGET based—E,UC3 22.6 21.3 21.8 20.8 18.3 17.4 16.5 1 In addition to all existing plant: plant where an appropriate contract is in place for connection to and use of the transmission system, less notified reductions in capacity from plant closures or plant being mothballed 2 In addition to all existing plant: plant that has obtained consent under section 36 of the Electricity Act and section 14 of the Energy Act 1976, less notified reductions in capacity from plant closures or plant being mothballed 3 In addition to all existing plant which is actually under construction, less notified reductions in capacity from plant closures or plant being mothballed. Source: National grid