DESNZ publishes a full set of conversion factors from 2012. For 2002 to 2011 it has republished electricity and heat only, so until today a gas bill or a business trip from 2008 had no factor in the app. We have now filled that gap from the guidelines Defra, and later Defra and DECC, published each year.

What is new

  • Fuels, vehicles and travel from 2002: gas, oil and other fuels, cars, lorries, flights, rail, freight and refrigerants. Motorbikes follow from 2007, and vans, buses, taxis and ferries from 2008. The 2007 edition has no lorry or freight figures.
  • Waste and water from 2009, and material use in 2011.
  • 7 editions, 4,056 factors. Coverage grows over time, from 120 factors a year in the 2001 edition to 1,129 in the 2011 edition.
  • An audit trail. Every figure is traced to an archived copy of the original file and the page or row it came from, with a record of anything left out and why.

Two limits are worth knowing. Editions before 2009 give many factors, such as fuels and electricity, in kg CO2 only rather than CO2e, and the app labels those lines that way. And older editions cover fewer activities, so some combinations still have no factor.

Who it helps

Any business whose baseline or earlier figures date from before 2012. If you are restating a baseline after buying a business or fixing an error, you may want each year worked out with its own year's factors. Now an old year's records can be worked out with the factors published for that year, rather than a later set.

The year makes a difference. As an example, an office burning 30,000 kWh of gas in 2005 produced 5.70 tonnes CO2 at that year's factor of 0.19 kg per kWh, against 5.47 tonnes CO2e at the 2026 factor of 0.18231.

How to use it

Add a past year's bills, mileage and travel with their real dates. The app picks the factor year from the dates, and each calculation line names the edition behind it, such as "Defra 2005 guidelines, kg CO2 only". Reports covering a year before 2012 include a method note saying so. For a Carbon Reduction Plan baseline before 2012 you still type in the Scope 1, 2 and 3 totals, which you can now work out in the app first.

The public factor pages show the older years too, marked with a footnote: see natural gas, petrol cars and short-haul flights, or browse every emission factor.