Midday electric grid demand in Britain at weekends has fallen below midnight levels from Monday to Friday, as a result of increased residential roof-top solar power generation.

Such changes illustrate the benefits from using smart meters to shift consumption to weekends, as British Gas proposed last week.

Weekend electricity demand has always been less than weekdays. But roof-top solar power has now pushed weekend midday demand – traditionally a peak – even below the lowest level in the middle of the night during the working week, shows the Balancing Mechanism Reporting System (BMRS).

The figures below show power demand in the last week of June, in corresponding weeks in 2016 and 2011.

They show demand minus roof-top solar power generation, which is presently not metered centrally, and so registers as a dip in demand. UK solar power capacity has now passed 10 gigawatts, from less than 1 GW in 2011, Department of Energy and Climate Change data show.

Figure 1. Electricity demand minus solar generation, megawatts, final week in June, 2016

UK power demand June 2016

Figure 2. Electricity demand minus solar generation, megawatts, final week in June, 2011

UK power demand June 2011

Figure 1 shows how midday grid electricity demand is slumping every day, according to how sunny it is. The midday slump was especially obvious on Monday and Saturday. As a result, midday demand on Saturday fell as low as 21,500 megawatts (MW) – below the lowest night-time level Monday to Friday.

Slumping weekend demand reinforces the opportunity from shifting UK power demand, to make better use of generation assets which otherwise are increasingly idle on Saturday and Sunday.

Centrica’s retail division British Gas has shown that is possible, last week introducing time-of-use electricity tariffs, heralding the much-anticipated load-shifting benefits of smart meters.

Smart meters allow electric utilities for the first time to monitor live gas and electricity consumption at the household level, and so offer reduced tariffs to consumers who use their appliances more at off-peak times. British Gas has offered free electricity consumption at the weekend for smart meter users.

UK power consumption data also show how demand is declining.

Last week, the highest peak demand was 37.3 gigawatts GW, on Tuesday, compared with a top peak of 42.8 GW in the same week in 2011. The difference, 5.5 GW, is nearly double the capacity of the proposed 3.2 GW nuclear power plant at Hinkley Point, due to come on line around 2025.

If utilities can successfully engage consumers in load-shifting (either from weekdays to weekends, or from daytime to night-time), then average and peak power demand may continue to fall, avoiding the need for such particularly large, outlier investments.

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