Carbon dioxide (CO2) is not the only greenhouse gas that contributes to climate change, but it is one of the easiest to understand, visualise and use in comparisons. CO2 equivalence (CO2e) is the method of converting all other greenhouse gases emitted during production and consumption of goods and services, like methane & nitrous oxide, to their equivalent value in CO2. This gives us a fair look at the relative impact of our actions in simpler terms.

We don’t believe you should be responsible for the emissions of all the products your country exports – only for what you consume. We wish to inform and empower you as a consumer, because ultimately the demand of goods and services is in your control. Using a consumption-based accounting model (CBA) also retains accuracy in instances where governments relocate dirty production to nearby countries to maintain a ‘green’ image.

It is not too late to mitigate the effects of climate change. Taking into account population growth and natural carbon sinks, the UN estimates that if we reduce our individual yearly footprint to 2 tonnes C02e by 2050, we can limit global warming to 2 celsius by 2100. The ecological and societal outcomes of meeting this target are vast, and our capacity to achieve it improves each year as sustainable energy, transport & food become widespread. If you’d like to find out more, check out the UN Paris Agreement & Global Sustainability Report.

We use information about your household type, number of residents, occupancy status, income and location to determine which of five electricity usage groups, detailed in the ABS residential electricity usage survey, you would most likely belong to. Your annual usage, (measured in KiloWatt hours, or KWH) is then adjusted to account for any gas water heating, carbon offsetting & sustainable energy sources. Tomorrow co. provides a carbon intensity measurement per KWH for each Australian state (or per MJ – megajoule – if energy source is gas). These have been calculated using real-time consumption statistics and a full lifecycle analysis of each energy production technology provided by the Intergovernmental Panel on Climate Change. We then multiply carbon intensity by your estimated annual KWH usage to get your final energy score. This score is then distributed according to yourhome.gov estimates on energy consumption, giving us a look at how much energy can be attributed to appliances, climate, water heating, lighting etc.

Tomorrow co. provides full lifecycle carbon modelling for each transport type per kilometer travelled (e.g. petrol car, hybrid, bicycle, walking etc). Calculations are also distinct for domestic and international flights, as their average air speed, capacities, efficiency & cargo ratios differ. The information you provide allows us to calculate the total distance travelled annually and therefore the total carbon intensity transport score. Options in the onboarding quiz that are a combination of multiple transport methods are calculated using the mean average intensity of those methods. (i.e. Public transport is the average of trains and buses per kilometer travelled).

Referring to your income estimates, we are able to use the ABS household expenditure survey to determine a breakdown of the goods & service expenses you are likely to have. This allows us to estimate the annual carbon intensity of individual products (such as light bulbs), or broader product categories (household durables), depending on the context. These figures are adjusted depending on which state you live in & whether you often purchase second hand. We then map these expenses to a product database provided by Tomorrow co. which estimates the carbon intensity of each Australian dollar spent in those product areas. Some examples of the products and services we are calculating the carbon intensity of are: financial services, clothing, appliances, durables, furnishings, cleaning equipment, electronics, toiletries and so on. We intend to continually add detail to this category as new data becomes available.

We calculate carbon intensity on a per meal basis, using the diet information you have provided. Each diet type has its own adjusted carbon intensity value provided by Tomorrow co., which takes into account age and sex in calculating an average daily intake. The values are further adjusted depending on whether you eat beef and/or dairy and if the food is sustainably sourced. We then calculate the carbon intensity of alcoholic & non alcoholic beverages using the same method as detailed in the purchases category, and add that to get the final score.

We start with the Australian household food & plastic waste averages, add in any disposables from the purchases category (e.g. paper towels, toilet paper etc) and then calculate the carbon intensity using the figures provided by the Tomorrow co. products database. We use adjusted life cycle stats for each waste material type, including average recycling rates. Your final score is then offset by the percentage of your food that is unpackaged & whether you compost your food waste.

The Bureau Of Meteorology estimates the carbon footprint of supplying Australian homes with water in each major district in the urban national report for water utilities. We take the mean of all major districts in each state to get a state average. This does not include the intensity of heating the water, so we have subtracted the total intensity of water heating (gas or electric) from the energy category and added it here for a more accurate look. We then distribute the score using yourhome.gov estimates to determine what percentage can be attributed to outdoor use, showers, toilet, laundry etc.