July 2017 saw the lowest average demand for electric power of any month in the last eight years in the UK.

Average half-hourly demand in July 2017 was 26.2 GW, the lowest monthly average in the last eight years according to energy data analyst EnAppSys.

While average half-hourly gross demand was 29.2 GW – a record low in itself – the high levels of embedded generation (3 GW on average per half hour) acting as demand reduction, took net demand down to this record level.
Solar power
GB demand has seen a general reduction over the past few years, as energy efficiency of consumer goods increases whilst energy-intensive industries decline.

More recently, this decline has been increased further as the amount of embedded generation on the system increases.  In particular, the effect of the solar power fleet on this demand reduction has been marked, with demand dropping substantially in the middle of sunny days.

In July, average solar generation between 10am and 2pm was 4.4 GW per half-hour, reducing demand by 13 per cent from the gross average of 34.1 GW.  GB solar capacity is now at 12.5 GW, with the fleet seeing a generation peak (and so demand reduction peak) of 7.3 GW on 17th July.

This increased presence of solar generation on the system has made it hard for thermal units which require long run times, in particular coal plant, to achieve the activity they are most suited to.  Coal-fired power generation in July 2017 was notably more sporadic than that last year, with average run hours per unit dropping to 107, from 153 in July 2016. 

This reduction in thermal generation has had knock-on effects on the system. July 2017 saw a spinning reserve of 2.52 GW, the second lowest across the last three years, after 2.50GW in May 2017.  This is 11 per cent lower than the 2.8 GW July average since 2014. System margin was also low in July 2017, at a record average of 13.3 GW, 16 per cent lower than the 15.9 GW July average since 2014.

Katie Fenn, analyst at EnAppSys, said: “The increase in embedded generation, particularly solar, has had a noticeable effect on the daily demand curve. It’s now common to see a dip in demand in the middle of the day.  Whilst this makes it difficult for large units to achieve long runs, and so reduces the spinning reserve online, this may not be such a big problem for system stability as it might appear, as fewer large units on line reduces the likelihood of a large single point of loss.”