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Creating a new NHS England: NHS England and NHS Digital merged on 1 February 2023. More about the merger.

Part of Sustainability Annual Report 2021-22

Annex 3 - Technical appendix

Current Chapter

Current chapter – Annex 3 - Technical appendix

Global pandemic

Nobody could predict the impact that the coronavirus (COVID-19) pandemic would have on all aspects of our lives and work or how long it would last. Due to the UK lockdown and majority of employees working from home, the pandemic had a significant impact on sustainability reporting. 2020-21 is being reflected as an exceptional reporting year, so whilst our data set and observations refer to year-on -year comparisons, the more credible comparisons can be made with pre-COVID reporting periods.

As we moved out of the extended lockdown phase and our offices started to reopen, NHS Digital’s hybrid working policy and guidance was introduced, and our hybrid working patterns have continued to evolve and stabilise through 2021-22. 

Baseline year

In previous years NHS Digital reported against a 2013-14 baseline. To align with a wider government re-baselining process, we now also report and measure against a 2017-18 baseline where possible. This re-baselining provides us with more ambitious goals that we are working towards achieving throughout the organisation. 

Scope of reporting

On a quarterly basis NHS Digital reports against the government's Greening Government Commitments (GGC). The GGC numbers make up a subset of this report. NHS Digital collects a wider set than the GGC scope requires, however the GGC scope still contributes towards our organisational footprint and has been used to inform some of the findings in this report.

Emissions performance (GGC scope)

NHS Digital’s performance contributes towards the Department of Health and Social Care’s (DHSC) targets, which for 2021-22 were to achieve a: 

  • 44% overall emission reduction (against 2017-18 baseline) 
  • 20% direct emission reduction (against 2017-18 baseline)

In 2021-22, against a 2017-18 baseline NHS Digital achieved:

  • 95% overall emissions reductions across all three emissions scopes 
  • 85% direct emissions reduction (Scope 1)  

The above reductions are relevant to the GGC scope, which as described above, is narrower scope than NHS Digital’s full organisational footprint.

Normalisation metrics

Performance is generally reported in absolute terms as the nature of sustainability challenges means that the goal is zero net damage. 

When estimating for utilities we have taken a pro-rata approach based on either square footage or FTE. See the Data Estimations and Assumptions section for more detail about specific cases.

Whole estate Gross Internal Area (GIA) and FTE normalisation metrics are as follows if the reader would like to assess in more detail. FTE includes permanent and temporary staff, secondees, agency temps, and contractors. 

2013/14 2014/15 2015/16 2016/17 2017/18 2018/19 2019/20 2020/21 2021/22
FTE 2,137 2,400 2,746 2,857 3,335 3,367 3,079 3,033 4,866
GIA (m2) 18,397 21,439 20,508 20,508 21,872 21,595 20,622 20,622 27,387*

*NHS Digital exited Skipton House and Trevelyan Square in 2021-22 and moved to 10SC in Canary Wharf and 7-8 Wellington Place in Leeds. As we have reported on all of these facilities, they are all included in the GIA total, causing it to appear inflated.

The GIA number is not inclusive of PHE sites.


Materiality at NHS Digital is largely considered in relation to carbon, as we are focused on meeting our net zero targets. 

Carbon analysis

The Greening Government Commitment carbon conversion factors have been used to calculate our absolute carbon figures, as well as the 2022 Department for Environment, Food, and Rural Affairs conversion factors when the GGC factors did not provide the necessary information. 

Data sources

Metric Accurate/estimate Source
Generator fuel use A Invoices
Building electricity/gas/water A/E Accounts/invoices/meter reads/estimated based on square footage or FTE
Colocation data centre electricity A Invoices
Fugitive gas (f-gas) leak tests A Leak test certificates
Lease cars/grey fleet A Expenses system mileage claims
Taxi, bus, tube E MTCO2e and consumption figures have been extrapolated from spend
Hotels, flights, trains A Travel booking data
Building waste A/E Weight data/estimates by square footage or FTE
ICT waste E MTCO2e and cost (£) were estimated based on volume
Paper use A Printing quantity from print reports
ICT hardware E MTCO2e was estimated based on spend
Hyperscale cloud A MTCO2e data from cloud providers
Outsourced data services E MTCO2e extrapolated from usage data

Data corrections and developments


Due to a data issue, water usage was reported incorrectly in 2020-21. It was reported we used 8,483m3. This has now been corrected to 11,024m3, and the equivalent carbon figure has been adjusted accordingly.


Cloud data

We continue to foster strong relationships with our cloud providers to ensure that we are able to report accurately on their contribution to our overall carbon footprint. This year showed a significant improvement in data access, and we will work with them to encourage further data transparency and availability.

Waste data

In previous years we were unable to access waste data for our estates and facilities, and therefore we were forced to estimate those numbers. This year we were able to get waste data from every facility, which has improved our visibility on our waste footprint. We continue to work with the facilities to maintain and improve on that level of data quality.

Data centres

Improvements in data from Redcentric data centres has meant that we have been able to move away from our previous years’ estimation methodology and our 2021-22 numbers are now based on accurate kWH usage and £ costs as provided by the vendor.
This improvement in data access explains the significant increase in co-location data centre electricity cost between the two years.

Data estimations and assumptions

Public Health England (PHE) sites

On 1 October 2021, responsibility for the National Disease Registration Service (NDRS) transferred from Public Health England (PHE) to NHS Digital, resulting in NHS Digital inheriting additional employee sites. Where NDRS employees were accommodated in existing NHS Digital sites, relevant data has been updated to reflect this. Estates data is not available as Actual or Estimate from the remaining small number of sites, so we have estimated for the following categories based on FTE:

  • generator fuel use
  • gas
  • building electricity
  • fugitive gas leak tests
  • water
  • recycling
  • waste to energy
  • waste to landfill 

We have estimated each of these categories according to our overall estate consumption by FTE, and then included them in our final consumption figures. The equivalent carbon and cost numbers have also been adjusted according to the consumption estimate, using the relevant carbon conversion factor, or using a £ per FTE rate for cost.

Estates and facilities 

Where invoices are charged against the entire facility, and we only occupy a portion, usage and costs have been calculated pro-rata according to the square footage we occupy.


VAT has been included in our absolute cost numbers, to be consistent with our previous years’ reporting. Any carbon calculations based on usage cost has been performed excluding VAT and any fees.



Smedley Hydro’s water usage was estimated for September and October 2021 based on an average of the usage across the other 10 months of the year.


Trevelyan Square gas for June 2021 was estimated due to no utility bill provided by the utility company. Numbers were estimated based on May’s daily usage and the exit date of 21st June. 

Waste cost

We have estimated our waste costs on a pro-rata basis based on square footage we occupy in the facility. For ICT waste, we took the cost per kg value which was used for estimations in last year’s report (£0.62 per kg) and multiplied the over ICT waste weight (18,000kg) by this factor. This was added to the estates and facilities waste cost to get an overall waste cost. 

Outsourced data services

This item represents data centre usage for the NHSmail service. Consumption in KWh has been estimated for October 2021 - March 2022 based on April 2021 – September 2021 data. This estimate has then been used to extrapolate a carbon figure.

Last edited: 4 November 2022 3:46 pm