Data and Sources
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Electricity Generation / Supply
Great Britain (GB) electricity generation or supply is made up of multiple sources and technologies. The generation contribution of each technology on the live dashboard is taken from the Balancing Mechanism Reporting Service (BMRS). This is produced by Elexon who run the wholesale electricity market and provide data publicly through a web service or API. BMRS's figures only include real time metered generation, and not embedded generation (see below for more info) and so additional data is obtained from National Grid (NG) ESO for embedded wind generation and PV Live for embedded solar generation.
For the live dashboard, 5 & 30 minute interval data is obtained from the BMRS. Where applicable 5 minute data has been correlated to the nearest half hourly embedded data from NG ESO and PV Live. The historical dashboard uses half hourly generation data from National Grid ESO.
Data can sometimes be delayed or parts of the received data is missing. No attempt has been made to correct for this, so occasionally gaps or delays will appear in the displayed information. Generation (power flow) is measured in gigawatts (where 1 GW = 1,000 Megawatts). Energy volume is normally measured in megawatt hours (MWh) but for consistency cumulative generation is displayed here at the same scale unit, gigawatt hours (GWh), or terawatt hours (TWh) on some of the historical data.
Click on the dropdown for more information on each generation technology and data sources:
The data for gas is mostly combined cycle gas turbines (CCGTs) as provided by Elexon (live dashboard) and NG ESO (historical dashboard). CCGTs combine a gas-fired turbine with a steam turbine, capturing waste heat to make the technology highly efficient. These power stations can be brought off or online within minutes and are used extensively to balance generation and demand e.g. when there are low wind speeds. Figures for open cycle gas turbines (OCGTs) are also added to the overall gas figure on the live charts. OCGTs are also used flexibly and can start and stop quickly and operate at partial loads. They might contribute up to 0.5GW when required, but over an annual period average out to around 0.03GW, or 0.1% overall generation and therefore have not been separated within the charts.
Data is provided by Elexon and NG ESO. Coal is becoming less important in the energy mix and the generation output is often at zero for several days or weeks in a row, having been displaced by gas and renewable technologies on windy and/or sunny days. New rules will force all coal power stations to close by 2025 as part of carbon emission reduction targets.
Data is provided by Elexon and NG ESO. Due to the complexity and cost of operating these power stations, generation output is normally consistent day on day (currently around 5-6GW) and forms part of the baseload of generation (along with biomass) .
Elexon's figures for real time metered wind farms are used which include all the offshore stations and the larger onshore wind farms (mainly in Scotland). The UK currently has approximately 28GW total installed wind capacity (of which around 14GW is offshore generation). On the live dashboard Elexon's data is combined with NG ESO data for (estimated) embedded wind generation to give the total wind figure. On the historical dashboard NG ESO data is used which includes embedded wind figures. Embedded wind capacity is currently estimated at around 6.5GW.
Data is provided by Elexon and NG ESO and includes coal-to-biomass conversions and biomass combined heat and power (CHP) plants. Biomass generation is fairly consistent day on day and forms part of the baseload of generation, along with nuclear.
On the live dashboard Elexon's import figures are used for the seven interconnectors which exist between the British mainland and other regions and countries. They include connections to Northern Ireland, France, Belgium, Holland, Norway and the Republic of Ireland. The total capacity of these interconnectors is up to 7GW and they can both import and export depending on supply and demand. On the historical dashboard NG ESO data is used which combines all interconnector flows
Data is for the renewable hydro (run-of-river) schemes, provided by Elexon and NG ESO.
Live dashboard data is from Sheffield University's PV Live service, updated every 30 minutes. Historical dashboard data is from NG ESO but originates from PV Live. The University are working in partnership with National Grid to model live PV generation across Great Britain, using representative sites which transmit live generation data. All PV generation is embedded, i.e. connected at the distribution level and not real time metered by National Grid. Installed solar PV capacity is currently around 13.9GW.
This is pumped storage hydro, which use electricity during low demand/cost periods (usually at night) to pump water up into a higher reservoir. This is released during periods of high demand and price, driving turbines to produce power. Data is provided by Elexon and NG ESO.
The 'misc' category is generation types not covered by the other categories (but still metered real time by NG), including spare power from a CHP plant at the Winnington chemical works. Data is provided by Elexon and NG ESO.
Carbon Emissions and Intensity
Carbon emissions and intensity data on the live and historic dashboards have been calculated using carbon intensity factors. Click on the dropdown below to view a list of the factors used and their sources.
Half hourly data for overall grid carbon intensity has been sourced from the Carbon Intensity API (live dashboard) and National Grid ESO (historical dashboard).
Hydro, Nuclear, Pumped Storage (PSH), Solar and Wind generation sources are assumed to have a carbon intensity factor of zero gCO₂/kWh (at point of generation).
| Generation Source | Factor (gCO₂/kWh) | Source | |
|---|---|---|---|
| 1 | Biomass | 120 | Carbon Intensity API |
| 2 | Coal | 937 | Carbon Intensity API |
| 3 | Gas (Combined Cycle) | 394 | Carbon Intensity API |
| 4 | Gas (Open Cycle) | 651 | Carbon Intensity API |
| 6 | Oil | 935 | Carbon Intensity API |
| 7 | Misc | 300 | Carbon Intensity API |
| 8 | Irish Imports | 458 | Carbon Intensity API |
| 9 | Northern Irish Imports | 426 | Grid Carbon |
| 10 | Dutch Imports | 474 | Carbon Intensity API |
| 11 | French Imports | 53 | Carbon Intensity API |
| 12 | Belgian Imports | 179 | Carbon Intensity Forecast Methodology |
| 13 | Norwegian Imports | 9 | Grid Carbon |
| 14 | Danish Imports | 185 | Grid Carbon |
Electricity Demand
The 'National Demand' is calculated as a sum of metered generation (generators which are conneced to the high voltage transmission system) and takes transmission losses into consideration. Elexon's published figures exclude generation required to meet station transformer load, pumped storage demand and interconnector exports. This is the 'net' demand on the live page (sometimes referred to as INDO - Initial National Demand Out-Turn, or NDF - National Demand Forecast).
'Gross' demand is a sum of metered generation and takes into account transmission losses and includes generation required to meet station transformer load, pumped storage demand and interconnector exports. This is also referred to as ITSDO - Initial Transmission System Demand Out-Turn, or TSDF - Transmission System Demand Forecast.
Published demand figures exclude embedded generation (mainly wind and solar with no real time metering) and are therefore lower than the generation figures especially during periods of high renewable generation. 'True' demand would therefore be the National Demand (net demand / INDO) plus the embedded generation connected to the distribution network, but there are no published figures for this.
What is 'embedded' generation?
Electricity generators can connect onto the network in two ways – at the transmission or distribution level. The transmission level is the main network which moves high voltage electricity around great Britain, connecting into large-scale generators e.g. coal power stations, large wind farms, nuclear, gas, hydro and biomass. The distribution level is the local network supplying cities and towns at a lower voltage. Embedded generation (or distributed generation) refers to electriciy / power generation or storage plants connected to the distribution network rather than the transmission network. These generators are 'embedded' into the distribution network, feeding electricity into it at a local level.
An important difference between transmission and distributed level generation is that National Grid (NG) ESO has visibility of the transmission generation through real time metering, but not at the distribution level. Embedded generation now accounts for a large proportion of the overall capacity of the electricity network (currently around 29%) and comes mostly from solar farms, smaller (onshore) wind farms and single wind turbines, combined heat and power (CHP) plants and (increasingly) battery / lithium ion storage. Small generators which are used intermittantly to meet peak demand, are also types of embedded generation e.g. diesel generators.
When embedded generators supply energy onto the distribution network, NG ESO do not see an increase in generation/supply, rather a reduction in demand and this can be clearly seen on windy and/or sunny days. This adds increasing complexity to how NG balance generation and demand, and maintain the system frequency within the statutory limits. It is acheived through real-time demand forecasting to predict the minute-by-minute demand change. With renewables contributing to the majority of embedded generation, weather forecasting is integral to maintaining this balance. Wind speed and solar radiation data is applied to a physical model which estimates output, based on installed capacity and location, which comes from a range of publically available information - ROC's, FiTs, BEIS and Renewable UK.