  Here we present a method to combine half-hourly publicly available electrical
generation and interconnector operational data for Great Britain to create a
timeseries that approximates its electrical demand. We term the calculated
electrical demand ESPENI that is an acronym for Elexon Sum Plus Embedded Net
Imports. The method adds value to the original data by combining both
transmission and distribution generation data into a single dataset and adding
ISO 8601 compatible datetimes to increase interoperability with other
timeseries data. Data cleansing is undertaken by visually flagging data errors
and then using simple linear interpolation to impute values to replace the
flagged data. Publishing the method allows it to be further enhanced or adapted
and to be considered and critiqued by a wider community. In addition, the
published raw and cleaned data is a valuable resource that saves researchers
considerable time in repeating the steps presented in the method to prepare the
data for further analysis. The data is a public record of the decarbonisation
of Great Britains electrical system since late 2008, widely seen as an example
of rapid decarbonisation of an electrical system away from fossil fuel
generation to lower carbon sources.
