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What happened to supply and demand in 2020?

GB electricity supply and demand in 2020.

Contribution made by all fuel sources

The data here are from the Elexon website, which includes data from all fuel sources, except solar. It gives separate data from Gas (CCGT), Coal, Nuclear, Wind, Biomass, the five interconnectors - French (IFA), Northern Ireland (Moyle), Netherlands (BritNed), Ireland (East-West) and Belgium (Nemolink) - plus all other minor sources.

This graph shows the contribution to grid demand throughout January 2020 as an example. Minor fuels have been omitted to give clarity:


Generation by fuel type Jan 2020


It can be seen that nuclear provided a reasonably steady base load at around 6700MW. Wind contributed between 1000MW and 13700MW. CCGT (hereafter referred to as gas), coal and biomass were being cycled to match fluctuations in demand and intermittency of the contribution from wind. There was also a significant level of imports via the interconnectors to meet peak demand.

The graph clearly shows that, as coal is being phased out and biomass is making a relatively small contribution, gas was the only power source which had the flexibility and controllability to provide the power required as demand on the grid increased and decreased over each day.

In summer, demand was much reduced due to warmer weather but also the lockdown caused to Covid 19.

Generation by fuel type Jul 2020


Nuclear again provided a steady base load at around 5200MW and the contribution from biomass had increased. Wind was again very erratic contributing little to demand on occasions due to extended wind lulls, often at times of high demand. Coal was not being used but again gas was being cycled to meet demand. A strange feature is that imports via interconnectors were often at their peak at weekends when demand was reduced.

The graph clearly shows that, in the absence of coal, gas was the only power source which had the flexibility and controllability to provide the power required as demand on the grid increased and decreased over each day.

Average contribution made by renewables and fossil fuels to demand

The Elexon data has been analysed to determine the average contributions to grid demand from gas, nuclear, wind, biomass, interconnectors and coal as shown in this table:

Average Contribution to Grid Demand (%) 2020
2018 Ave41.922.

Gas was by far the highest contributor, almost totalling nuclear and wind combined. The nuclear contribution provided a base load and wind contributed almost 25% on average. Interconnectors were making a larger contribution to the grid demand than in the past averaging almost 10%. Coal is being phased out, but is still required at times of peak demand, particularly during the winter months.

By comparison to 2018, gas has decreased by about 10% and coal has halved. Nuclear has also dropped by about 10%. Biomass has increased by about 40% and imports via interconnectors by about 15%, but the most significant increase is in wind which is almost 60% higher. This would appear to be a significant shift away from the need for fossil fuels but these averages mask what was really happening. What was critical was how the various fuel sources could be controlled.

Minimum monthly contributions

The next table shows the minimum contributions from gas, nuclear, wind, and biomass each month. (Interconnectors and coal are omitted as they are controllable and often not brought on stream and show zero as their minima.) As demand fluctuates month by month and hour by hour, the data is presented in terms of percentage contribution:

Minimum Contribution (%) 2020
2018 Range7.3-19.612.2-19.50.2-2.81.3-4.9


Important points to note:

  • Gas contribution is controllable and the minimum level of electricity supplied by gas has increased since 2018.
  • Nuclear again provided a steady contribution. (Note: a reactor was taken off load in summer explaining the low minimum in August.)
  • As in 2018, there was a time in every month when wind could not be relied upon to make any significant contribution to demand due to extended wind lulls.
  • Biomass provided additional capacity as required.

We can now use the information above to answer some specific questions.

How did renewables contribute to demand on average through 2020?

From the Elexon website, the official source for power being fed into the grid, the contribution from nuclear in 2020 averaged about 20% of demand, providing an input of between 15.3% and 24.9% in any month. This did not vary with demand and so provided a steady base supply.

Although wind contributed almost 25% on average, it dropped to a minimum of between 0.4% and 2.4% from month to month. This variation was due to the lack of wind and not to any variation in demand.

How did this compare with contributions from fossil fuelled power stations?

In 2020, gas was by far the biggest contributor to demand, supplying 37% on average with an input varying between 27.4% and 46.4%. (It should be noted that the lowest contribution was in February when the contribution from wind was unusually high.) Output from CCGT stations was of course being controlled to meet demand. Coal was only used when demand exceeded supply from other sources and was not used at all for three months in the summer.

How was peak demand met?

It is clear from the graphs and tables above, that whilst nuclear provided a steady base supply, the fuels being used to meet peak demand were gas, biomass, interconnectors and, to a lesser extent, coal. Wind cannot be relied upon to provide power at times of peak demand as output is intermittent and unpredictable.

As coal is phased out, it is obvious that CCGT Gas is the only fuel source which can be controlled to meet the ever fluctuating demand on the grid. Therefore, if there is to be any technology in the power supply field in GB designated as key then it must be gas.

Can renewables meet demand in the future or will GB have to continue to rely on fossil fuels?

The answer to this question is that it depends on the renewable power source. Although nuclear can provide a steady base contribution, some form of controllable renewable sources will be required to meet the bulk of demand at peak times. This cannot be wind.

Wind turbines may contribute to reducing the need for gas, and hence reduce carbon emissions, when the wind blows but are totally unreliable in producing power as and when required by fluctuating demand.