Conversion of energy data to footprint

Get footprint in kilograms of CO2-equivalents for energy usage by category

All inputs, outputs and defaults can be seen in the Convert energy technical API docs.


This endpoint receives:

  • a data source to base calculations on
  • a list of energy categories, associated to a value and its unit
  • optionally the date for which the footprint should be computed

At least one category must be provided. Values in kWh or litres of fuel used are optional. If you have not submitted optional data, you get the conversion factor for the given category in return. If no date is given, the current date is taken as the default.


This endpoint returns, for each category:

  • footprint in kilos CO2e, rounded to grams

Note that the footprint for energy includes the full life cycle emissions of energy usage, for consumer communication, which is far beyond greenhouse gas reporting requirements. If you’re interested in the GHG reporting use case, head over here.


Category name



Electricity as delivered to households by the grid


Energy generated from the combustion of biomass such as wood


Energy generated from the combustion of liquid fuel, such as via a furnace or boiler


Energy obtained from distributed heat generation via a central location, from the combustion of e.g. biomass, refuse or oil


Describes the national average of all energy used, which is typically a combination of the aforementioned energy sources.


Energy obtained from LPG gas or similar


Energy obtained from photovoltaic installations in households


If energy use is given in litres, conversion factors are used to convert the amount to energy in kWh. The energy consumption (in kWh) is multiplied with the corresponding multiplier of the energy source in order to calculate the emissions.

The date also influences the calculations. We account for technology changes (more efficient solar panels and wind turbines, greener electricity mix etc.) and temporal effects (higher energy prices and emissions intensity in winter) and their impact on your footprint. For example, if you compute your energy footprint during summer, it will be lower than the footprint in winter (while keeping the energy use constant).


The sources and methodology used to obtain the multiplier for each category is detailed below.


For European data sources, the electricity multiplier is calculated based on monthly electricity generation data from Eurostat.  The amount of energy generated by each source of electricity is multiplied with a multiplier obtained from  the IPCC 5th assessment report or Tranberg et al. (2019). This allows us to  calculate a European average electricity mix, which we think is the most relevant metric for tracking the footprint of electricity use. The European energy market is highly interconnected, and Ducky prefers a marginal approach when considering the potential gains of saving or reducing energy use. We therefore argue that the direct physical origin of the electricity (“where are the electrons in the cables going to my house coming from”)  is not relevant when considering climate impact, we must employ systems thinking. See this article detailing our standpoint.


The multiplier for using wood for heating is obtained from Arvesen et al. (2018). We use the overall average although the data would allow us to distinguish between different types of trees, stoves efficiencies, etc.


The multiplier for burning fuel oil is obtained from the UK’s Department for Business, Energy & Industrial Strategy’s yearly greenhouse gas reporting: conversion factors report. The numbers in this report are combined with an additional “well-to-tank” factor to describe the emissions associated with extracting and refining the oil, to give a more accurate life cycle estimate.


The multiplier for gas is obtained from this paper by Ricardo Energy & Environment . This is combined with an additional “well-to-tank” factor to factor in the emissions associated with all the upstream processes. The WTT factor is taken from the study by Exergia (2015).

Solar panel

The multiplier for solar panels is obtained based on the work of Louwen et al. (2016), from which we find an average factor for kg CO2e/Wp. This is further combined with data about the average solar panel installation size and efficiency specific to Norway, obtained from experts in Asplan Viak, from which we obtain a factor for kg CO2e/kWh. This factor is based on a life cycle assessment of producing the photovoltaic system (both the panels, the casing and installation), which are spread over an assumed lifetime of 30 years. 

District heating

The multiplier for district heating is highly source dependent. This is because the emissions depend on the source of the heat, which could be fossil fuels, garbage, electricity, biogas, or recovered heat. For Norway, Fjernkontrollen maintains an overview of the various energy sources used for district heating, from which Ducky’s partner Asplan Viak extracts a multiplier in kg CO2e/kWh. In our current data, a factor for biogenic CO2 of 0.61 is used, reflecting the fact that although organic matter grows back and reabsorbs the carbon it emits, this takes decades and there is therefore a temporary warming effect. Emissions related to heat generated from waste incineration are economically allocated between waste treatment and heat.

National household average

The multiplier for the national average energy mix is calculated using a top-down method. From environmentally-extended input-output tables, we know the total emissions due to energy consumption in households in a year, which can then be used to calculate the  energy footprint in kg CO2e per household. Based on our model for the energy use of households (see Calculate Energy documentation), we can find the energy consumption of an average household per year. Dividing these factors by one another gives a multiplier in kg CO2e/kWh for the average energy use on a national level.

See also intro to convert endpoint overview with related endpoints. 

Note that the related convert finance endpoint can convert an energy expense into footprint.