Before calculating Balancing System Use of Service (BSUoS) charges for assets, the first stage of the process is determining which assets are liable to charges. There are two main factors influencing BSUoS charges for battery energy storage system (BESS) assets: if an asset is directly connected to the transmission network or via a distribution network, and if an asset is exporting or importing energy. Table 1 (below) shows a summary of when BESS assets are liable for BSUoS charges. (To learn more about which assets are liable to BSUoS charges and the policy behind this read our article here.)

Using our internal database, we filter to transmission-connected assets and estimate their BSUoS charges using the actual half-hourly BSUoS price from National Grid, and then multiplying this value by the estimated throughput when exporting. The BSUoS price used is the Interm Initial (II), as this data is available for the time horizon needed at the time of publication of the Leaderboard.

Prior to the policy changes that occurred in April 2021, distribution-connected assets were charged for importing and received embedded benefits when exporting. To estimate their BSUoS charges, the net energy throughput was calculated on a settlement period basis, multiplied by the half-hourly BSUoS price to calculate the charges they were liable to pay or receive, and then aggregated for the month.

Before April 2021, there were no transmission-connected BESS assets in Great Britain, so this was never calculated on the Leaderboard.

To find out more about how BSUoS works, watch our Energy Academy video here.