Your footprint uses the UK government's greenhouse gas conversion factors for 2026 (Department for Energy Security and Net Zero). Scope 1 is the gas or oil you burn on site, plus fuel for company petrol or diesel cars, counted per distance driven. Scope 2 is the electricity you buy, using the government's single figure for UK grid electricity, which is what you use for carbon reporting, plus charging for company electric cars away from your premises. Scope 3 currently covers business flights, counted per passenger and including the extra warming effect of emissions at altitude, assuming about 1,000 km each way for a short-haul flight and about 6,500 km each way for a long-haul flight. It also covers homeworking: the government factor is per working hour for one person working from home, covering the extra heating and equipment use, and we assume 7.5-hour days and 46 working weeks a year.

We estimate how much electricity your premises use in every half-hour of a typical year, based on the building type, floor area and opening hours (or your own bills, if you add them). For offices, the daily electricity pattern comes from measured meter data: recent half-hourly data from a London office (2023–25), blended with 36 European office buildings from the Building Data Genome Project 2. The heating pattern comes from the same building's half-hourly boiler gas data, so a heat pump's extra electricity is added on the days and in the seasons when the building needs heat, mostly in winter. Heat pumps run more steadily than boilers, at lower output for longer, so within each day we spread 40% of the heat pump's load evenly and keep 60% following the boiler pattern. That matches monitoring of UK homes, where on cold days heat pumps drop to about 41% of their peak overnight, compared with 16% for gas boilers (University College London, using the government's Renewable Heat Premium Payment trial data). Each day's total, and the pattern across the year, stay the same. Published half-hourly data for heat pumps in offices is limited, so this is an estimate; we don't yet model heat pumps working less efficiently on the coldest nights. Other building types use a simpler pattern based on opening hours until measured data is added. Each upgrade changes that pattern: LED lighting lowers use while you're open, solar panels generate during daylight, a battery moves use from one time of day to another, and a heat pump replaces boiler fuel with electricity.

Each half-hour of change is multiplied by the carbon intensity of the electricity grid in your region at that time of day, in that month, using 2025 data. This matters because grid power is usually cleaner in the middle of the day and dirtier in winter evenings, so the same kilowatt-hour saved can be worth very different amounts of carbon. Solar power you send to the grid is counted as displacing grid power at the time it's exported.

For comparison, we also show the same saving using the national grid for Great Britain (measured half-hourly data for the same year), and using the UK government's single figure for grid electricity, which is what standard UK carbon reporting uses. The gap between that figure and your local, half-hourly one shows what a standard report misses.

Energy attribute certificates (EACs) record changes in consumption, not only renewable generation, so they capture what happens behind the meter that grid-level certificates like REGOs miss. We count electricity saved by LED lighting, solar power used on site and electricity a battery moves to cleaner times. Exported solar is left out to avoid double counting with REGOs. Certificates for heat pumps are still being developed; in the meantime, the gas or oil a heat pump avoids is shown as a separate option that could be sold for a fixed period.

Gas and oil use carbon factors from the UK government's greenhouse gas conversion factors. Building energy use starts from typical benchmarks for each type of premises, which vary a lot between real buildings, so these are indicative estimates only. An installer's quote and your actual meter data will give firmer figures.

Regional carbon intensity data: Carbon Intensity API, National Energy System Operator, licensed under CC BY 4.0. Regional values are modelled estimates.