Electricity emissions methodology
The sum of the products of the half-hourly consumption and the corresponding grid intensity at the meter postcode.
This is the only calculation permitted by Perseus, defined at https://registry.core.sandbox.trust.ib1.org/scheme/perseus/process/electricity-emissions-calculation/2026-03-12
Detailed process:
- Retrieve half-hourly electricity consumption from the Energy Data Provider (EDP) in kWh. This may have been recorded directly by a smart meter, or in the case of partial occupancy it may come via a building management system from a sub-meter or a calculation based on number of occupiers or floorspace.
- Pull the corresponding half-hourly grid emissions for the first part of the meter address postcode (the “outcode”, which is also provided by the EDP) from carbonintensity.org.uk. Specifically https://carbon-intensity.github.io/api-definitions/#get-regional-intensity-from-to-postcode-postcode (kgCO2eq/kWh)
- Multiply the half-hourly electricity consumption by the half-hourly grid intensity to get electricity consumption half-hourly emissions (kgCO2eq)
- Produce a report of monthly emissions to an FSP of the SME’s choice by summing half-hourly emissions for whole months where data is available. For example if data is available from 2025-05-15 to 2026-03-26, provide monthly data for 2025-06-01 to 2026-02-28. Example report here
More details on the background to the methodology can be found in section 4 of the appendices to the Perseus 2024 report.
Gas emissions methodology (after 2026-03-12)
The sum of the products of the half-hourly consumption in cubic meters and the most recent published greenhouse gas conversion factor for natural gas covering the time of consumption.
This is the only calculation permitted by Perseus, defined at https://registry.core.sandbox.trust.ib1.org/scheme/perseus/process/gas-emissions-calculation/2026-03-12
Detailed process:
- Retrieve half-hourly gas consumption from the Energy Data Provider (m3). This may have been recorded directly by a smart meter, or in the case of partial occupancy it may come via a building management system from a sub-meter or a calculation based on number of occupiers or floorspace.
- Retrieve the most recent Natural Gas emissions intensity figure covering the consumption period from Defra (kgCO2eq / m3). This is updated annually and there is no API for it.
- Multiply the half-hourly gas consumption by the gas emissions intensity to get gas consumption half-hourly emissions (kgCO2eq)
- Produce a report of monthly emissions to an FSP of the SME’s choice for whole months where data is available. For example if data is available from 2025-05-15 to 2026-03-26, provide monthly data for 2025-06-01 to 2026-02-28. Example report including electricity and gas here
There is a discussion paper covering the gas methodology in the Perseus 2025 Report accompanying documents