We have developed a carbon calculator and tracker which is simple to use and will enable you to track your carbon footprint from year to year. You can access the tracker here.
An earlier spreadsheet version can now be downloaded here.
What datasources do we use?
The calculator uses the following data sources:
- Greenhouse Gas reporting factors published annually by government.
- Annual Household expenditure statistics published by ONS
- Our world in data carbon impacts data. This has a download link for carbon footprints different basic foods.
- How bad are banana? book by Mike Berners-Lee
Why do we ask for the year?
There are two reasons that we ask for the year:
- Annually government produces factors that are used for company greenhouse gas (GHG) reporting, we need the year to determine which set of factors to use.
- We build a table of carbon footprints for each year, together with a set of targets for following years.
Number in household
We calculate both a household footprint and a per person footprint, this recognises that many emissions are shared between a household. The personal figures are simply the household figure divided by the number of people in the household. You need to enter this for each year, as the number may differ from year to year.
Home energy use
Home energy use can be calculated very accurately, particularly if the fuel you use is metered. You enter the amount of each of the following types of fuel you use in a year, you can select fuel types from
- Electricity (grid only)
- Mains gas
- Wood logs
- Wood pellets
- Wood chips
- House coal
- Manufactured smokeless fuel
then you enter the amount of fuel used using appropriate units, you can enter as many fuel rows as you need.
Standard factors for each year are applied to your home energy use to work out your footprint.
We have worked out a simple way of accomodating both conventional ICE vehicles, plug in hybrids (PHEV) and battery electric vehicles (BEV)
For each vehicle you need its annual mileage, which you can get from its MOT certificate (unless it is less than 3 years old), fuel consumption (petrol/diesel). Many cars have a trip computer which shows average consumption over the car’s life, this is the easiest way of getting your consumption.
If you don’t have a trip computer you need to gather data over a calibration period, and press the calculate button to input the mileage and litres of fuel used in the period (it is clearly important to start and end with the same fuel gauge reading).
Plug-in vehicles (both BEV and PHEV) are often charged at home using electricity that has already been accounted for in your home electricity consumption, so you need to enter only mileage that does not use home electricity. You will need to enter your electricity consumption, you can probably get this from the car’s computer, and the mileage travelled on public charging electricity.
For each vehicle you should choose a fuel from electricity, petrol or diesel and then enter the consumption and mileage. If you have a plugin hybrid (PHEV) then you should enter two rows one for electricity from public charging points and one for petrol/diesel.
It would be nice if you could keep a food diary and enter the precise amount of each food you ate, and it worked out your carbon footprint. Unfortunately this would take a lot of your time, and would require a large amount of data to drive it. Some information on the carbon footprint of various foods is given by our world in data. This data gives raw foods, so could be a useful indicator, but leaves out things that are processed that we might eat such as biscuits, ready meals and so on.
Your food and drink expenditure should include both home and away from home consumption.
We have instead built an approach based on five diet types and your annual expenditure on food and drink:
- Plant Based
- Light meat eater
- Standard UK
- Heavy meat eater
Diets that are only plant based have far lower emissions than any other.
Vegetarian diets include dairy produce and eggs which have quite high emissions.
Light meat eater diets include poultry and fish and very occasional red meat.
The standard UK diet includes some red meat, and follows a similar profile to ONS household expenditure.
The heavy meat eater diet is one which has a portion of red meat almost every day. Red meat such as beef, lamb and venison has higher emissions than other foods. There is also much more variability in red meat emissions, depending on land use change, feed, and even breeding.
I have also looked into beef and lamb a bit more, as the figures given in the above are global averages. This link https://ourworldindata.org/environmental-impacts-of-food#you-want-to-reduce-the-carbon-footprint-of-your-food-focus-on-what-you-eat-not-whether-your-food-is-local shows that beef emissions vary between 9kg CO2e/100g and 105kg CO2e/100g. This is too big a range to ignore. I came across an industry report which seems to get emissions at a farm level http://beefandlamb.ahdb.org.uk/wp-content/uploads/2013/04/roadmap_3_-_down_to_earth_180112-final-report.pdf. This sort of thing might be more useful as it could direct consumers to good farms.
Stuff covers goods and services, it is everything else that you consume, except for occasional new expenditures such as:
- New buildings and extensions
- New cars
Other renovation work on buildings (or cars) should be included in this section
You enter the amount you spend annually on goods and a standard factor is applied to calculate your emissions.
A standard amount of emissions is allocated to emissions.
- Tobacco and Narcotics
- Clothing and footwear
- Maintenance and repair of dwellings
- Water supply
- Household goods and services
- Medical products, appliances and equipment
- Purchase of vehicles, spares and servicing
- Communications equipment (phones, etc)
- Audio-visual, photographic and information processing equipment
- Major durables for recreation
- Other Recreational items, gardens and pets
- Newspapers, books and stationery
- Personal care and personal effects
- Rent and mortgages
- Hospital services
- Postal and communication services
- Recreational and cultural services
- Package holidays
- Social protection
- Other services – professional, legal, banking, etc.
How is stuff calculated?
The calculation for stuff is the least accurate of our calculations.
For goods the underlying assumptions are:
- Emissions of 1100 kg CO2e per person, which CAT have calculated from UK industrial and commercial emissions.
- 2.3 persons per household to give household emissions of 2530 kg CO2e
- UK Consumption emissions of 784 Mt CO2e
- UK Production emissions of 503 Mt CO2e
- Household emissions are multiplied by the ratio of consumption emissions to production emissions (1.55) to give 3943kg CO2e
- This is divided by average household expenditure on goods of £8725 from analysis of ONS household expenditure data to give 0.4519 kg CO2e/GBP
This factor is multiplied by the amount you spend on stuff to give your emissions.
The fixed amount for services is based on an estimate of 3000kg CO2e per standard household of 2.3 people equivalent to emissions of 1304kg CO2e per person. Unlike the other estimates it isn’t based on expenditure, this is because things in this category that we spend a lot of money on such as rent, mortgage, council tax will have roughly the same emissions regardless of what is spent.
Large expenditure items
Some occasional large expenditure items should not be included under goods:
- New buildings and extensions
- New cars
New Buildings and extensions
New building and extensions are better represented by the total floor area of new building with some adjustment for the type of construction. Much of the cost of a new build is for the land it stands on, buying the land doesn’t cause emissions.
We have derived a figure per square metre for standard UK domestic buildings of using an average new build embedded emissions of 68t CO2e and an average total floor area of 93m2 for all buildings after 2003 giving 731kg CO2e/m2.
Buildings whose construction is predominately concrete have a higher level of embedded emissions, which is estimated at 877kg CO2e/m2.
Similarly timber framed and off-site fabricated buildings have lower emissions, which is estimated at 585kg CO2e/m2.
If you have built or intend to build you can calculate the embedded emissions from your build more accurately, the calculator gives you the alternative of entering a known emissions figure. Performing this calculation is beyond the scope of this calculator, here are some links that may help:
- UK Green Building Council: Practical Howto Guide – measuring embedded carbon on a project.
- Embedded Carbon Calculator Beta (US)
- Embodied Carbon Footprint Calculators for Construction
- The Urgency of Embodied Carbon and What You Can Do about It
- Embodied Carbon – The ICE Database
For new cars we have found that embedded emissions relate most closely to the kerb weight of the vehicle, with an addition for battery electric vehicles (BEVs).
Standardised information on embedded emissions from vehicle manufacture is hard to find. Carbon Brief have written a fact check on how EVs can help tackle emissions which is informative.
This article concludes with a summary of lifetime and embedded emissions for a number of different vehicles drawn from the carbon brief report. We have derived a factor based on kerb weight (which can be found in the manufacturer’s literature) for each of the vehicles given in the table at the end. This table has also been used to calculate an addition for BEVs.
For BEVs a large part of the embedded emissions are due to electricity consumed during battery production. Batteries constructed in Europe and North America use electricity with lower emissions than Asia. Fortunately most vehicles sold in the UK are made either in the UK or Europe. Many factories now include their own renewable energy source to lower their electricity emissions.
Leased and Rented vehicles
If you lease a new vehicle for a long term (two or more years) then you are deemed to be responsible for its embedded emissions just as if you had bought a new car.
If you lease or rent a vehicle for a shorter period than 2 years you are responsible for a proportion of its embedded emissions.
The calculator has been tested with Chrome and Firefox. It should work with the majority of browsers.
If you have any issues with using the calculator please comment below.