How the clock change impacts UK energy demand
With the clocks scheduled to go back one hour this Sunday 27th October, we take a look at the impact this will have on UK energy demand.
The clocks are scheduled to go back one hour this Sunday 27th October. The change will cause an obvious shift in usage of the electricity system as evenings draw in earlier in the day.
It also accelerates the seasonal trend towards higher demand during the colder, darker winter months, placing increased pressure on power margins. This can lead to spikes in electricity prices, should supplies struggle to meet the higher demand.
Jump in demand decreases as overall downward trend continues
As forecasts currently stand, the average peak demand for the week following the clock change will be 4.4% higher than the week before. Consumption is expected to rise by almost 2GW as lighting usage increases during the traditionally higher post-work demand period.
| Average Weekday Peak Demand | Weekly average before Clock Change (GW) | Weekly average after Clock Change (GW) | Difference (GW) | Increase (%) |
| October 2019 (Forecast) | 38.9 | 40.6 | 1.7 | 4.4% |
| October 2018 | 40.0 | 43.6 | 3.6 | 9.0% |
| October 2017 | 40.7 | 43.7 | 3 | 7.4% |
| October 2016 | 42.2 | 44.8 | 2.6 | 6.2% |
| October 2015 | 43.9 | 45.2 | 1.3 | 3.0% |
| October 2014 | 43.0 | 44.0 | 1 | 2.3% |
However, the forecasted rise in average peak demand in 2019 is lower than in recent years. Notably 2018 which saw the highest percentage change, as consumption rose by almost 4GW week-on-week.
Overall peak power demand has been dampened marginally this year, with consumption after the clock change peaking at 40.6GW on average, 3GW lower than last year. This reduction can be attributed partly to half-term school holidays, which fall on the week either side of the clock change depending on school catchments. Higher renewable levels have also contributed to reductions in demand.
The ongoing trend in reduced energy consumption year-on-year continues, meaning that demand is rising from a far lower base. Improvements in energy efficiency have been helping to reduce electricity use over the last ten years. A large part of the reduction in peak demand has been the use of new technology, resulting in smart and more efficient appliances, able to do more with less.
Expected demand before this month’s clock change is 5GW lower than the highest peak in 2015. Furthermore, the forecasted post-clock change peak is the lowest on record.
The role of renewables
The increase in wind and solar capacity in recent years has contributed to the overall demand reductions. Higher volumes of on-site renewable capacity allow more generation to be provided off-grid as homes and businesses generate their own electricity supply during windy or sunny spells. This reduces demand on the national transmission system. The high levels of solar availability during the summer season were a particularly strong influence on demand levels this year as on-site solar panels increased embedded generation. This reduced demand requirements for the transmission network.
Wind power continues to deliver a growing percentage of the UK electricity mix. By the end of September 2019, the UK’s fleet consists of over 10,000 wind turbines with a total installed capacity of over 21.5GW. Overall wind generation in the UK has so far been 33% higher through 2019 than over the same time period last year.
What happens when there’s no wind?
While high winds have the capability of cutting power demand, one of the biggest dangers to the National Grid electricity network is a high demand scenario, at a time when wind output is very low.
Lighting has a bigger impact on electricity demand than heating, as the majority of home heating is gas-fired. However, during severe cold snaps, electricity demand does spike as additional heating is needed to cope with the very low temperatures. This scenario occurred during the Beast from the East cold snap in February last year. However, robust winds provided high levels of low cost electricity to the grid.
A lack of wind would see supply margins placed under significantly more stress during a similar cold snap this winter. This would require additional supply being provided by gas and coal plant or imports to make up for the increased demand. Such a scenario is likely to require significant price rises in the Within-day and Day-ahead markets.
The National Grid’s Winter Outlook for 2019/20 expects that there will be a sufficient supply margin to accommodate a wide range of security of supply scenarios. However, the organisation’s statistical 1-in-20 peak demand forecast predicts a demand of 499mcm/d, greater than the highest recorded gas demand. This is an unlikely scenario, but demonstrates how a period of high demand and low renewable availability could coincide to increase short-term prices.
An end to the clock change?
There have been proposals dating back to 2015, from members of the European Parliament, to end summer time observance. In September 2018 the European Commission proposed an end to seasonal clock changes, asking that member countries decide by March 2019 which time they would observe year round. The proposal was approved in March 2019, by 23 votes to 11. However, the start date has been postponed until 2021 to allow a smooth transition.
The United Kingdom is due to leave the EU before the reform becomes effective, meaning that it would be left to the government to make their own decision on observing summer/winter time. If continued, Northern Ireland would have a one-hour time difference for half the year with either the Republic of Ireland or the rest of the UK. The House of Lords launched an inquiry in July 2019 to consider the implications of this, with a call for evidence ongoing.
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