Electric vehicle public charging infrastructure statistics: Methodology note
Updated 30 April 2024
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Introduction
This methodological note accompanies the electric vehicle public charging infrastructure statistics release series. It provides background information about the data used and the methodology behind the statistics produced for this release series.
How to use statistics and data in this release series
Due to our contractual agreement with Zapmap, we cannot provide further breakdowns beyond what is published in this release series or the underlying precise device location data. Although it has relatively limited coverage, the National Chargepoint Registry (NCR) does provide device location data.
As we source data from Zapmap, we request that any reference to this statistical release series is clearly attributed to Zapmap as well as the Department for Transport (DfT).
Please ensure you take the limitations discussed in this methodology note into account when interpreting or using the statistics in this release series.
Quality
These statistics are released under the ‘official statistics in development’ label – formerly called Experimental Statistics. Official statistics in development are official statistics that are temporarily undergoing a development and are being tested with users, in line with the standards of trustworthiness, quality, and value in the Code of Practice for Statistics.
These statistics do not meet the rigorous quality standards of accredited official statistics, for example with respect to partial coverage.
We welcome feedback from users of these statistics. This can be provided via electric vehicle charging infrastructure statistics.
Development plan
This statistical release series presents quarterly updates to publicly available electric vehicle charging infrastructure in the UK. It intends to inform users (both internal and external to government) about the roll out of public charging across the UK, including on key issues such as regional and local authority provision, and the proportion of devices at different power ratings. The release series is not designed as a complete picture of charging infrastructure due to incomplete data coverage and because it does not contain data on devices inaccessible to the public, for example those installed in workplaces or domestic properties, some of which may have been installed via government grants.
As these statistics are labelled official statistics in development, this release series is undergoing a development phase, in an effort to increase our understanding of the quality, accuracy, reliability and value of these statistics. We expect this release series to remain labelled as official statistics in development for the foreseeable future. Electric vehicle charging infrastructure is a rapidly developing policy area, so this release series may develop alongside changes in policy and user interest. For example, in October 2023, we updated device speed category definitions to align with policy and industry, and added new statistics covering devices by rural urban classification (RUC) and at parliamentary constituencies, to add value to the release series. Furthermore, the recently announced Public Charge Point Regulations 2023 may present opportunities to develop the contents of the release series as it comes into force in the coming months.
The data used and the methodology behind how we produce statistics in this release series are explained in this methodological note. Limitations to our data and to the interpretations of the statistics are also explained here, to maximise the trustworthiness of our statistics, and we are regularly reviewing ways to mitigate these as part of this development phase.
We welcome feedback from users of the statistics, which can be provided via electric vehicle charging infrastructure statistics.
Data source
The public charging device data in this release series is sourced from the electric vehicle charging platform Zapmap. The data we present in this release series has been cleaned and quality checked. It represents a snapshot of publicly accessible devices across the UK reported as operational at midnight as at the last day of each quarter. For example, the statistics covering the first quarter of 2024 were released on 30 April 2024 and presented data correct as at midnight 1 April 2024.
As the data represents available devices at a snapshot in time, please note that an increase in device numbers between 2 points in time reflects the total net increase in charging devices between the two snapshots of data. Charging devices are captured in this total when they are added to the dataset, which is not always the same as when they were installed. Decommissioned charging devices are also removed from the total number. An increase in devices therefore reflects the net increase between the 2 snapshots of data in that period rather than the number of installations in that period.
Coverage
Zapmap report that they have coverage of over 95% of public charging. Chargepoint operators supply information about their devices to Zapmap, and the public can notify Zapmap about devices not already on their network. These data do not cover privately owned domestic or workplace devices that are not accessible to the public. This means that the total number of all electric vehicle charging devices across the UK will be higher than estimated in this publication.
There is no way of assessing whether data coverage of public charging devices is better in some geographical areas than others, and there are currently no other sources with similar coverage against which we could verify Zapmap’s data. The National Chargepoint Registry’s (NCR) coverage is less comprehensive than Zapmap’s, however it does provide more detailed information on each charging device than is available in this release series, including the exact location of devices and their number of connectors.
How we measure charging infrastructure
In this release series we present statistics on charging infrastructure by referring to ‘charging devices’. Devices are physical units with connecting sockets capable of charging the batteries of plug-in electric vehicles. Each charging device may offer one, or multiple connecting sockets. Some devices can charge only one vehicle at once, and others can charge multiple simultaneously, which means that some devices have greater charging capability than others regardless of the number of sockets, therefore, we do not cover charging sockets in this release series. Zapmap data does not indicate whether devices can charge only a single vehicle or multiple vehicles simultaneously.
There are often multiple charging devices near one another. As devices can sometimes charge multiple devices simultaneously, charging capability is likely to be higher than the number of charging devices in any given location.
As we continue to develop this official statistics in development release series, we will be considering how we measure charging infrastructure and we welcome feedback on this.
The term ‘chargepoint’ is also sometimes used in discussions about charging infrastructure. It was used in previous statistical publications from the DfT. This may refer to either a single device or a number of connectors on a device which can be used simultaneously. We no longer use ‘chargepoint’ in statistical contexts, however the term is still used in other contexts.
Data cleaning
The data we receive from Zapmap is cleaned and quality checked prior to inclusion in this release series. Our data processing includes removing charging devices located in the Channel Islands (as this release series covers the UK only) and charging devices which are designed for charging hydrogen-powered electric vehicles.
Speed categories
Charging devices are often grouped into different charging speed categories that are determined by power rating bandings and labelled according to a common naming convention. Speed categories are used in this release series and by government and industry to indicate how quickly a device can charge an electric vehicle. Until October 2023, in this statistical release series, we categorised devices into one of the following speed categories:
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slow devices: 3kW to 6kW
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fast devices: 7kW to 22kW
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rapid devices: 25kW to 100kW
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ultra rapid devices: 100kW plus
To align with changes across industry, charging devices in this release series and elsewhere are now categorised into the below speed categories. These categories are still determined by power rating bandings, however, the Office for Zero Emission Vehicles (OZEV) are working with industry on a common naming convention. Until this is determined, in this release series we will refer to the new categories by their power rating banding only:
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3 kilowatts (kW) up to 8kW
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8kW to 49kW
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50kW to 149kW
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150kW and above
Charging devices can have several connectors of various speeds. To allocate a device into a speed category, we take the device’s most powerfully rated connector and assign the device to the speed category that this connector belongs to.
Location categories
Charging device location categories are defined based on the facility they are located in and who can access this and the type of charging service they provide. Device locations are labelled by Zapmap. In this release series, they are grouped into one of the following location categories.
On street - charging devices located on residential streets only.
En route - charging devices located for charging to continue a journey. Located in motorway service areas, service stations, electric forecourts and ferry terminals. Additionally 50kW and above charging devices in hotels, restaurants and attractions.
Destination - charging devices located at the end of a journey or where a driver may typically stop for an extended period of time. Consists of both 50kW and above and 49kW and below charging devices located in retail car parks, car parks, leisure, education areas and transport (except ferries), in addition 49kW and below charging devices located at hotels and restaurants.
Other - charging devices which are semi-public with some level of access restrictions such as workplace car parks and dealership forecourts.
These categories are used in this release series and by government and industry.
Charging device geography in our data and statistics
This release series contains statistics and data on the number of charging devices within the UK’s administrative geographies such as regions, local authorities, and parliamentary constituencies. We match device locations to these administrative geographies using data, definitions and boundaries set by the Office for National Statistics (ONS). Access the ONS Geography Portal to see the geographical area covered by any administrative geography in our statistics.
The local authority administrative geographies used are up to date as of April 2023. Parliamentary constituency data is sourced from the Office for National Statistics Geography Portal for 2021. The administrative geographies in this release series are subject to change alongside changes to local authority areas or parliamentary constituency boundaries.
To compare device provision while accounting for large population differences across the countries and regions of the UK, we present the number of devices per 100,000 population in addition to the raw number of devices. The most recent population figures are sourced from the ONS Population estimates for mid-year 2021. For quarters from July 2020 to April 2021, the population figures were sourced from 2019 estimates. For quarters before April 2020, population figures were sourced from the 2018 estimates.
Rural urban classification
Since October 2023, we have published a time series on the number of charging devices by rural urban classification (RUC) in England. This is to better understand charging provision in different settlement contexts across England.
The RUC system we use is the ONS’s 2011 rural and urban classification (RUC2011), which groups output areas (small geographical areas for use in statistical analyses) in England into one of four urban or four rural classifications. To determine the RUC of public charging devices, we use each device’s lower layer super output area (LSOA), which is already matched to one of the RUC2011 categories in data taken from the ONS Open Geography Portal. More information on RUC2011 can be found on the ONS website.
These statistics are limited to England only. RUC2011 applies to England and Wales only, other countries in the UK have different methods for classifying areas as rural or urban, and so cannot be compared to statistics on England produced by using the RUC2011 classifications.
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Electric vehicle charging infrastructure statistics