Last week, to little fanfare, National Grid published its review of the UK’s electricity and gas markets for the 2015/16 winter period. Despite literally dozens of reports in the press at the start of the winter warning of the very high risks of blackouts, the lights remained very firmly on.

The reports were right to warn of the risks – UK supply margins are low and getting lower, with yet more coal plant closing in 2016, and an increasing reliance on intermittent generation in the system.

Firstly, we can look at the actual supply and demand gap in the winter just gone:

supply and demand

This doesn’t seem that bad, with a nice gap between the two lines indicating that there wasn’t much real danger of blackouts over the period. Weather corrected transmission system demand was 1.0 GW lower at peak than was forecast by National Grid in their Winter Outlook Report, with the difference being largely due to an increase in embedded generation (small generation sources connected to local distribution networks which act to reduce demand on the transmission system), and customer demand management.

The supply was made up as follows:

generation mix

Gas contributed more than coal this winter, and wind generation was significantly higher than the previous year. However, wind has much lower and more variable availability than thermal and nuclear generation, as shown in the next chart:


The past winter followed the recent meteorological pattern with gloomy, dull but not particularly cold weather, with temperatures above the long-term average. There were relatively few days of high pressure systems, where the conditions are cold, clear and still (ie high demand and low wind output).

Winter 2016/17 will be the last in the UK before the capacity market deliveries start, and it will be interesting to see how tight the system will be. Chances are that the lights will stay on, but the risks are increasing…a winter high pressure system combined with a thermal plant or two tripping would be certainly make things pretty uncomfortable.


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