BSC Insight: Why Non Half Hourly electricity use increased in the first four months of 2021

In this insight article Emma Tribe, our Analysis and Insight Senior Product Analyst, explains how the colder temperatures between January and April 2021 increased Non Half-Hourly electricity demand.

Through our analysis of electricity Suppliers’ Non Half-Hourly metered data, we have found that:

  • The first four months of 2021 were colder on average than the same months in 2019 and 2020;
  • There was an increase in electricity demand for Non Half-Hourly electricity suppliers during this time despite an overall decrease in electricity demand due to COVID-19 restrictions; and,
  • The long-term trend for Non Half-Hourly electricity demand shows that overall electricity demand is decreasing year on year.

Non Half-Hourly electricity demand

Properties that have meters, but do not have their meters read Half-Hourly are Non Half-Hourly. These type of properties are often residential and small and medium businesses. As electricity is settled in half hourly Settlement Periods, meter reads from Non Half-Hourly meters need to be converted into Half-Hourly data. For this, we use a process called profiling.


Elexon use profiling to convert electricity meter reads, or estimated electricity demand, into energy usage for each half hour Settlement Period. Elexon then use these Half-Hourly profiled volumes in electricity Settlement.

For more information on how load profiles work, we recently published a BSC Insight article detailing how COVID-19 impacted Load Profiles.

Since 2010, Non Half-Hourly electricity suppliers have generally seen decreases in their customers’ electricity demand. This is due, in part, to energy efficiency measures such as insulation and more energy efficient electric appliances being installed in homes across GB.

However, during the first four months of 2021, electricity Suppliers saw an increase in electricity demand. This is detailed in the below graph.

Changes in Non Half-Hourly electricity demand

The left hand graph shows the total Non Half-Hourly Electricity Demand in January, February, March and April for each year since 2010. The right hand graph shows the percentage change in total Non-Half-Hourly electricity demand for the same four months compared to the previous year. If you would like to explore the data further, filters are included on the right hand side to enable you to filter by month and GSP Group.

The Non Half-Hourly Electricity Demand for the first four months has decreased in seven out of the 11 years shown, with the greatest decreases in 2011, 2014, 2017 and 2019.

The four years with increases in Non Half-Hourly electricity demand are 2013, 2015, 2018 and 2021. The biggest percentage increase is 2021 with 5.63%. Whether the electricity demand increases or decreases compared to previous year is related to whether it was warmer or colder than the previous year.


Changes in average noon temperature

This graph above has the same layout as the previous graph, except it is for average noon temperature for the first four months of each year since 2010.

Comparing the two graphs, you can see the inverse effect temperature has on Non-Half-Hourly demand. The years with the biggest increases in temperature are the same years that have the biggest decreases in energy demand (2011, 2014, 2017 and 2019).

The four years with increases in Non-Half-Hourly electricity demand are also the four years with the biggest decreases in average noon temperatures (2013, 2015, 2018 and 2021).

Relationship between temperature and Non-Half-Hourly electricity demand

This graph plots for each day in January, February, March and April the Great Britain average noon temperature and the total Non-Half-Hourly electricity demand on that day. You can filter the data by month and year, as default 2010, 2020 and 2021 are the three years shown. Use ctrl+click to select or deselect multiple years.

For the temperatures in these first four months, in each year there is a clear linear relationship between temperature and Non Half-Hourly electricity demand. This is why noon temperature is an input to calculate the Non Half-Hourly electricity profiles.

What is the correlation coefficient

The correlation coefficient for each year is between -0.73 and -0.93. Correlation coefficients tell us how much linear correlation there is between two variables.

The gradient of the slope of the trend line for each year is between -11GWh/oC and -17GWh/ oC. The gradient tells us how much the daily Non Half-Hourly electricity demand will increase by for every degree of temperature increase along the trend line. Since there is an inverse linear relationship between these two measures for these four months, the gradient is negative.

Warm weather and Non Half-Hourly demand

It is worth noting that temperature and Non Half-Hourly electricity demand no longer follow the same sloping linear relationship when temperatures get above 15oC. At temperatures above 15 oC the daily total Non Half-Hourly electricity use tends to stay between 400GWh and 300GWh. This is because in Great Britain warmer temperatures have less of an impact on Non Half-Hourly electricity demand than cooler temperatures. In other countries where air conditioning is widespread in homes and small businesses you would expect to see increases in electricity use above a certain temperature.

Cooler temperatures were the main cause of the increase in Non Half-Hourly energy use in the early months of 2021. We make this claim based on the fact that there were more days with lower temperatures in the four-month period in 2021 than in 2020. By accounting for the year on year fluctuations in temperatures, we can see that trend line between temperature and Non Half-Hourly electricity demand is similar in 2020 and 2021.

As you click through the years from 2010 to 2021 in the final graph there is an underlying trend for the trend lines. The y-intercept (electricity demand for the trend line at 0 oC) is decreasing, in 2010 the y-intercept was 626GWh and in 2021 the y-intercept was 514GWh. The y-intercept is 18% less (112GWh) in 2021 compared to 2010. This shows that Non-Half Hourly electricity customers are using less electricity at lower temperatures.

Demand and Net Zero

More efficient electricity use in homes and small businesses contributes to Great Britain’s net zero goals. It reduces the need for additional electricity generation, which could be from burning additional fossil fuels in thermal power stations when the temperatures get colder. Thermal generation also tends to be less efficient at lower temperatures as it takes more fuel to warm up the water to produce steam at a cooler ambient temperature.

Note on the data sources

Temperature data is sourced from Supplier Volume Allocation Group (SVG) approved weather stations.

Non Half-Hourly electricity demand for suppliers currently a confidential data set that cannot be shared publicly. Elexon use this data to monitor supplier performance and market trends.


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