Methodology

Giki Zero is a step by step guide to help people understand, track and reduce their carbon footprint. With individuals making up more than 70% of global emissions the targets to reduce emissions by 2030, and reach Net Zero by 2050, are only possible if people live more sustainably.

Giki Zero combines a detailed, science based, carbon footprint tool and over 150 steps to help people find ways to reduce their footprint which suit their lifestyle and budget.

We provide our methodology so that users can understand the calculations behind Giki Zero. We also hope it will be useful to other people who are looking to calculate individual carbon footprints. If you do use our methodology please do let us know and cite Giki Zero where appropriate.

Giki Zero provides estimates for a person’s environmental impact based on a series of footprint models which are categorised in sections. These are home, transport, food, purchases, services and trees.

Footprint estimates are based on consumption which in turn can be an average amount (based on country, region or global data), an estimate (where we provide a user with the ability to select options to help them estimate their footprint) or actual data where a user provides with specific consumption information.

Consumption estimates are then multiplied by conversion factors in order to estimate footprints for carbon, land and water. These are carbon dioxide equivalents (CO2e), water usage (litres, l) or land usage (square meters, m2).

In order to account for the fact that some footprints are for the individual but some are shared models are split between those which are for an individual or those which are shared across the household. For example, a diet footprint estimates the impact from an individual’s diet but an electricity footprint calculates the impact for a whole house and so is shared across household members.

User input is given based on the current calendar year and continuation is assumed from period to period.

All of the estimates provided in Giki Zero are exactly that, estimates. Footprint models will evolve over time based on improved estimation as well as updated, or improved, data. For example, a number of the main data sets used by Giki Zero update annually and see material changes in impact measurement both due to calculation enhancements and changes in impact as providers of goods and services respond to the need for decarbonisation. For example the CO2e emissions per kWh are decreasing in many countries across the world as renewables increase in the energy mix.

Where individuals want a more personalised footprint with lower estimation error they should enter actual data whenever possible. This is possible in the majority of Giki Zero footprint models.

Giki’s mission is to help people live more sustainably and so a full methodology is provided to ensure both transparency of how footprints are calculated but also as a source for others trying to do the same or for others to provide suggestions for how Giki Zero can improve. Where possible data sources have been chosen which are publicly available.

Home

Electricity Footprint

Electricity footprints are calculated for the household as a function of electricity used and the CO2e emissions per unit of that electricity.

Average values are based on mean electricity consumption for all dwelling types based on double adult occupancy and average supplier CO2e emissions for the relevant country or region. In some countries, e.g. the UK, users are able to select specific suppliers. This is done where the individual supplier mix is available. In others, e.g. the Global region, users can select from a list of countries to improve the estimation process.

For usage estimates are most often taken from national surveys of energy use. This includes the National Energy Efficiency Data in the UK where, in turn, Giki uses property type and a bedroom proxy based on quartile ranges to estimate usage across different house sizes. Further country data sets include EIA RECS, the UN and Eurostat. CO2e emissions factors are taken from a number of sources including electricityinfo.org, eGrid, EIB and Climate Transparency. Defra conversion factors are used to account for transmission and distribution emissions. The latter explains why green electricity providers still have an electricity carbon footprint.

Sources

Additional Model specifications

  • Electricity footprints are calculation for a household and then divided among household occupants in equal proportions.
  • Refinements taken from various sources including Energy Savings Trust.
  • Grid factors may be updated for time to time following material changes.

Gas Footprint

Gas footprints are calculated for the household as a function of gas used and the CO2e emissions per unit of that gas.

Average values are based on mean gas consumption for all dwelling types based on double adult occupancy and Defra gas conversion factors. In some countries, e.g. the UK, users are able to select specific suppliers where “green” gas is available. Providers of green gas are adjusted supplier by supplier using their % of green gas out of total gas.

For usage estimates are most often taken from national surveys of energy use. This includes the National Energy Efficiency Data in the UK where, in turn, Giki uses property type and a bedroom proxy based on quartile ranges to estimate usage across different house sizes. Further country data sets include EIA RECS, the UN and Eurostat.

Average values are based on mean gas consumption for all dwelling types based on double adult occupancy.

Users can provide their meter readings in either kWh or m3.

Sources

Additional Model specifications

Water Footprint

Carbon footprints from water usage (the amount of CO2e emitted to supply and treat water usage for a household) are calculated for a person based on the consumption (average, estimated, or actual) in m3, or cubic feet, multiplied by carbon emissions from Defra conversion factors accounting for both supply and treatment.

Averages are based on medium usage per person for a two or three person household. Estimates are based on a 2 person household. National surveys are used to estimate water usage as low, medium, high or very high .

Sources

Additional Model specifications

  • Water footprints are calculation for a household and then divided among household occupants in equal proportions
  • Refinements are taken from various sources including Southern Water
  • Updates may be made from time to time if there are material changes in emission factors estimations.

Oil Footprint

Oil carbon footprints are calculated for a household based on consumption (estimated or actual) in litres multiplied by carbon emissions from Defra conversion factors for heating oil. For estimated usage low, medium, high gas usage is estimated based on average energy usage in a country or region.

Because only a small proportion of households use oil for their energy (e.g. under 5% of the UK population have oil fired heating) we use a median of zero for the typical person.

Sources

Additional Model specifications

  • Oil footprints are calculation for a household and then divided among household occupants in equal proportions

Wood Footprint

Wood footprints are calculated for the household as a function of wood used and the CO2e emissions per unit of that wood.

Average values are not included as the median wood consumption is zero.

Sources

Additional Model specifications

  • Per Household model
  • Refinements are based on DEFRA outside of scope estimates and with a default that individuals use sustainably sourced wood or gather it themselves.

Waste Footprints

Household waste carbon footprints are calculated for a household based on consumption (average, estimated or actual) in kg multiplied by carbon emissions for different waste types from Defra conversion factors.

Average and estimated waste is taken from country or regional sources including WRAP and The World Bank. Estimates of recycling rates chosen by users correspond to a scaling factor where the maximum recyclable remains within the boundaries of the most common consumer outcomes.

Sources

Additional Model specifications

  • Waste footprints are calculation for a household and then divided among household occupants in equal proportions. Assumes that households have food waste recycling

Home improvement footprints

Home improvement carbon footprints are calculated for a household but are in early stages given a lack of LCA (Life Cycle Analysis) data looking at house repairs, renovations and services. As an initial approximation CO2e per unit of currency spent is calculated using average household spending on household maintenance and repairs and price conversion factors from Defra. Although price conversion factors are a common method used (e.g. for linking bank accounts) our preference is for actual conversion factors in the long term.

Sources

Additional Model specifications

  • Home improvement footprints are calculation for a household and then divided among household occupants in equal proportions.

Transport

Tube and Light Rail Footprint

Tube and Light Rail (e.g. trams and metro) carbon footprints are calculated for a person based on consumption (average or estimated) in km travelled multiplied by carbon emissions per km from Defra conversion factors.

Averages distances are from the national travel surveys and average journeys taken are from the same source where possible.

Sources

Additional Model specifications

  • Tube and Light rail footprints are calculated for an individual.

Rail Footprint

Rail carbon footprints are calculated for a person based on consumption (average or estimated) in km travelled multiplied by carbon emissions per km from Defra conversion factors.

Averages distances are from the national travel surveys. Distance travelled based on time is taken from a sample of trips using Google maps.

Sources

Additional Model specifications

  • Rail footprints are calculated for an individual.

Taxi Footprint

Taxi carbon footprints are calculated for a person based on consumption (average, estimated or actuals) in km travelled multiplied by carbon emissions per km from Defra conversion factors using per km data.

Averages distances are from the national travel surveys and average journeys and total miles / km are from the same source where possible.

Sources

Additional Model specifications

  • Taxi footprints are calculated for an individual.

Bus Footprint

Bus carbon footprints are calculated for a person based on consumption (average, estimated or actuals) in km travelled multiplied by carbon emissions per km from Defra conversion factors using per km data.

Averages distances are from national travel survey and average journeys and total miles / km are from the same source combining different bus modes.

Sources

Additional Model specifications

  • Bus footprints are calculated for an individual.

Ferry and Ship Footprints

Ferry and ship carbon footprints are calculated for a person based on consumption (average, estimated or actuals) in km travelled multiplied by carbon emissions per km from Defra conversion factors using per km data.

Averages distances are from national travel surveys and distances come from country or regional sources including UK Sea Passenger stats (UK only) and WFPGEO Node.

Route distances are from searoutes.com.

Sources

Additional Model specifications

  • Ferry and ship footprints are calculated for an individual.

Cruise Footprints

Cruise carbon footprints are calculated for a person based on consumption (average, estimated or actuals) in carbon emissions per day using averages from cruise line meta study. The median for Cruise footprints is zero.

Sources

Additional Model specifications

  • Cruise footprints are calculated for an individual.

Car Footprint

Car usage carbon footprints are calculated for a person based on consumption (average, estimated or actuals) in km travelled multiplied by carbon emissions per km from Defra conversion factors using per km data for different car types. Car types are estimated based on size and engine or actuals based on data from country or regional sources including the Vehicle Certification Agency (UK) and US Dept of Energy (US). Average distances are taken from national travel surveys.

Car ownership carbon footprints are calculated using the World Auto Steel UCSB Model 5 for different engine types and size. Production and lifecycle values are computed and adjusted for average car lifetime and a per annum estimate is then calculated on a straight line basis.

Sources

Additional Model specifications

  • Car footprints are calculated for an individual.

Flight footprint

Flight carbon footprints are calculated for a person based on consumption (average, estimated or actuals) in km travelled multiplied by carbon emissions per km from Defra conversion factors using per km data adjusted for different aircraft classes.

Average distances and average CO2e per km are a weighted average of short, medium and long haul flying for a typical person using national travel surveys. Estimated distances are calculated by using common destinations for short, medium and long haul flights with short, medium and long haul definitions from eurocontrol. Actual distances are calculated on a great circle basis using airport latitude and longitude from openflights.

Sources

Additional Model specifications

  • Flight footprints are calculated for an individual.
  • Individuals should include personal flights only as work flights should be allocated to company operational footprints.

Motorbike Footprint

Motorbike carbon footprints are calculated for a person based on consumption (average, estimated or actuals) in km travelled multiplied by carbon emissions per km from Defra conversion factors using per km data adjusted for different motorbike types.

Distance travelled is from national travel surveys where the median is most often zero as only a small proportion of the population ride a motorbike.

Sources

Additional Model specifications

  • Motorbike footprints are calculated for an individual.

Food

Diet Footprint

Diet carbon, land and water footprints are calculated for a person based on consumption (average, estimated or actuals) of different foods groups in a representative diet multiplied by a conversion factor per kg for food, per m2 for land and per litre for water for those food groups.

Representative diets are taken from national and regional surveys of consumption and calorie supply (e.g. National Diet and Nutrition Survey for UK, FAO for global and other countries) and is calorie adjusted (note that additional calories are covered by Food Waste footprints).

Estimated diets (e.g. Vegetarian) are calculated on a calorie neutral basis and removing the food groups that are not appropriate, for example the vegetarian diet excludes all meat and fish while the no red meat diet does the same for beef and lamb only. Overall calorie consumption is maintained at the same level normally by scaling up other food groups to account for food groups excluded although in the case of some diets legumes (which are not represented in the NDNS diets) and other food groups are scaled up by a greater amount in order to ensure a balanced overall diet. Diets described as “mainly” plant based or vegetarian follow the same process using a weighted average where 90% of the diet is plant based or vegetarian whilst 10% is based on the typical diet.

Calculations for the CO2e, m2 and litres per kg are taken from academic meta studies including Poore and Nemecek (2018) and the Centre for Sustainable Systems dataField These studies are combined, where necessary using a common framework for food categories following Foodex. Averages are taken across food groups and studies in order to mitigate the impact of wide ranges of outcomes for different foods based on LCA boundaries, geographical variation and growing and processing differences.

Sources

Additional Model specifications

  • Diet footprints are calculated for an individual.

Food waste Footprint

Food waste carbon, land and water footprints are calculated for a person based on amount of food, in kg, that is thrown away each year. Estimates are based on surveys of food loss and regional statistics in particular the UNEP Food Waste Index Report 2021.

Estimates are calculated based on survey information and adjusted for different levels of food waste. Data includes eligible food meaning that, when estimates are used, the Food Waste footprint cannot drop to zero. Conversion is based on averages for different diet types (e.g. throwing out meat will have a high food waste footprint than throwing out vegetables) with conversion factors for the CO2e, m2 and litres per kg (following the Diet footprints) are taken from academic meta studies including Poore and Nemecek (2018) and the Centre for Sustainable Systems dataField These studies are combined, where necessary using a common framework for food categories following Foodex. Averages are taken across food groups and studies in order to mitigate the impact of wide ranges of outcomes for different foods based on LCA boundaries, geographical variation and growing and processing differences.

Sources

Additional Model specifications

  • Food waste footprints are calculated for an individual.

Pet Footprint

Pet carbon, land and water footprints are calculated for a household based on the number of pets (average or actual) and the carbon, land and water usage related to their food.

Average pet numbers are proxied by the UK comparing the the Pet Food Manufacturer’s pet population survey adjusted for the number of people in the UK.

Food footprints are calculated based on the calorie requirements of cats and different breeds of dogs which comes from Ohio State University’s Veterinary Centre whilst dog breed sizes are from the American Kennel Club. Cat breeds are taken from Wikipedia.

Calorie requirements are then multiplied by the average CO2e per calorie taken from a typical diet.

Sources

Additional Model specifications

  • Pet food footprints are calculated for a household and allocated equally between each member of the household.

Purchases

Clothing footprint

Clothing carbon and water footprints are calculated for a person based on the number of items purchases (average, estimated or actuals) multiplied by the amount of carbon or water used to produce each item.

Average items purchased are taken from the European Clothing Action plan in kg per person per year as is water usage per tonne. Carbon conversion factors are from Defra. Estimated clothing is based on group average weights (small, medium, large and footwear) with individual clothing weights estimated using information from delivery service companies. Final CO2e per item calculations are cross checked against individual LCA studies.

Sources

Additional Model specifications

  • Clothing footprints are calculated for an individual.

Appliances footprint

Appliance carbon footprints are calculated for the household based on consumption of appliances (average, actual) multiplied by the carbon emissions per unit. Consumption is estimated using national household spending surveys which gives total annual spending and adjusting to units purchased using a representative sample of appliance prices based on internet searches. Appliance calculations are split between small and large items.

LCA Emissions per unit are taken from WRAP’s report “Reducing the Environmental Cost Impacts of Electrical Products” taking total embodied GHG and volume data to estimate per unit emissions as well as estimates from individual company reports. CO2e per unit of currency factors are also used for cross checking.

Sources

Additional Model specifications

  • Appliances footprints are calculated for a household and allocated equally between each member of the household.

Electricals footprint

Electrical item carbon footprints are calculated for a person based annual expenditure from national and regional expenditure surveys with conversion factors taken from Defra price conversion factors. The wide range of electrical items makes this an approximation only.

Carbon footprints are cross checked using individual LCAs (predominantly from Apple adjusted for production values only) and WRAP’s report “Reducing the Environmental Cost Impacts of Electrical Products” taking total embodied GHG and volume data to estimate per unit emissions.

Sources

Additional Model specifications

  • Clothing footprints are calculated for an individual.

Personal care footprint

Personal care footprints are calculated for a person based on the amount spent on personal care items (average, estimated) multiplied by the CO2e per unit of currency spent which, in turn, is based on LCA studies from personal care companies.

The average amount spent on personal care comes from household expenditure data adjusted for average household size or population where appropriate. CO2e per unit of currency spent is calculated from company LCA studies which calculate per kilogram or item and adjusted for average item prices. As such the personal care footprints represent, at best, an approximation until a greater number of LCAs becomes available.

Sources

Additional Model specifications

  • Personal care footprints are calculated for an individual.

Household Cleaning footprint

Household cleaning footprints are calculated for a household based on the amount spent on household cleaning items (average, estimated) multiplied by the CO2e per unit of currency spent which, in turn, is based on LCA studies and Defra price conversion factors.

The average amount spent on household cleaning comes from national household survey expenditure data adjusted for average household or population size where appropriate. Estimated amounts are simple ranges around the ONS average. CO2e per unit of currency spent from LCA studies calculates per kilogram or item and adjusted for average item prices. As such the household cleaning footprints represent, at best, an approximation until a greater number of LCAs becomes available.

Sources

Additional Model specifications

  • Household cleaning footprints are calculated for a household.

Furniture footprint

Furniture footprints are calculated for a household based on the amount spent on furniture (average, actual) multiplied by the CO2e per item which, in turn, is based on LCA studies and Giki estimates.

The average amount spent on furniture comes from the household survey data which is divided by the average price of a representative sample of products from internet research for UK footprints. For other countries and regions consumption is converted using Defra price conversion factors. CO2e per item comes from industry LCA studies and Giki approximations where no LCA has been found. The latter are based on furniture weight and material mix converted to CO2e using Defra conversion factors for different materials (wood, plastic, glass and soft furnishings).

Sources

Additional Model specifications

  • Furniture footprints are calculated for a household.

Services

Recreational service footprint

Recreation service (e.g. cinemas, gyms, live events) footprints are calculated for an individual based on the amount spent on Recreation services (average only, not estimates available due to limited information on carbon footprints of these services) multiplied by the CO2e per unit of currency spent from Defra price conversion factors.

At present there is limited data on recreational services including different amounts used by households to help estimation.

Sources

Additional Model specifications

  • Recreation service footprints are calculated for an individual.

Mobile and internet footprint

Mobile and streaming footprints are calculated using approximations based on co2e per unit of currency for mobile footprints and company analysis (Netflix, Google) for streaming and internet usage. The carbon footprint of internet services is often over reported which is discussed by Carbon Brief.

Sources

Additional Model specifications

  • Mobile and internet footprints are calculated for an individual.

Pharmacy footprint

Pharmacy footprints (covering purchases in the pharmacy) are calculated from expenditure information (not including health services) using CO2e to unit of currency conversion provided by Defra.

There is no estimation available at the moment owing to limited information. The main reductions in Healthcare carbon footprints are likely to come from healthcare providers.

Sources

Additional Model specifications

  • Pharmacy footprints are calculated for an individual.
  • Update January 2021: Switch to co2e per £ for conversion factors in UK to improve estimation process

Accommodation footprint

Accommodation footprints are calculated for a person based on accommodation night stays (average, estimated) multiplied by per night CO2e per occupied room.

Average accommodation night stays are taken from country or regional tourism surveys and CO2e per night per room is from the CHSB Hotel footprinting tool looking at different hotel types for popular destinations (5stars, 4stars and 3stars). These are cross checked with Defra conversion factors for hotel stays.

Sources

Giki estimates for self catering and camping

Additional Model specifications

  • Accommodation footprints are calculated for an individual.

Financial services footprint

Financial services footprints are calculated for a person based on the amount in GBP, USD, EUR (average, estimated, actual) of financial assets multiplied by the CO2e per currency unit of those assets.

Financial assets are separated into savings (bank accounts, cash savings), investments (bonds and equity investments) and private pensions.

CO2e per unit of currency invested are estimated by analysing the amount of carbon dioxide emitted, for both equity and debt financing, by fossil fuel companies from each of those financial asset groups. It is not a measure of overall portfolio carbon emissions, which may be higher, to avoid double counting with other footprint calculations. For individuals who want to see their entire portfolio carbon footprint their financial service company is the best source.

Estimates for investments and pensions have been calculated in 2 ways and cross checked. Method 1 uses CDP Scope 1&2 data for large fossil fuel companies (including Shell, Total, BP, Equinor, Occidental) and dividing by the total Enterprise Value (EV) to give a Scope1&2 CO2e per unit of currency of EV. An equally weighted average of the different fossil fuel companies is taken with outliers removed. Method 2 used information on fund statistics from the fantastic Fossil Free Funds website taking energy portfolios with high fossil fuel exposure. Portfolio weightings are taken from representative 60/40 funds or benchmarks for pension. Investments are assumed to be held in both cash and equity and bond markets.

Where a user selects fossil fuel free we assume that the portfolio has 0% weighting in fossil fuels and because this is the part of the portfolio we are measuring the carbon footprint goes to 0. As noted above this is different to a standalone analysis to avoid double counting of an individuals footprint. When a user selects ESG investments the adjustment is based on the lower weighting of ESG funds in fossil fuels companies which is about half of standard funds.

CO2e per unit of currency saved are estimated by analysing the lending by banks to fossil fuel companies, as a percentage of their overall loan book, using the same scaling factor from CDP data of carbon per unit of EV. This applies to savings. The main data source is the Rainforest Action Network Banking on Climate Chaos report.

More specifically for savings emissions.

Savings. Three step process to estimate carbon emissions from financing. 1) Analysis of bank balances sheets to ascertain percentage of loan book that goes to fossil fuel industries 2) Calculate the amount of carbon emitted per unit of currency of finance based on CDP data 3) combined the exposure to fossil fuel lending with the carbon emissions per unit of exposure to give an estimate of CO2e per unit of currency.

Unlike other carbon footprints these measures represent carbon that is emitted on behalf of, rather than directly controlled by, individuals. However, as the individual benefits in terms of capital appreciation, dividends and income, and they have the ability to change, it is included in Giki’s’ footprints. However, the calculations only include emissions from fossil fuel companies to avoid double counting. For example when an individual invests in an Energy company and uses fuel in their car the Scope 1&2 emissions are covered by the portfolio investment but the actual emissions from burning fuel are covered in the car footprint. Full portfolio carbon emissions may be much higher highlighting the important of Net Zero porfolios.

Sources

Additional Model specifications

  • Financial Services footprints are calculated for an individual.

Trees

Carbon removal through nature based solutions such as tree planting is an important part of achieving Net Zero. However, removals should be for residual emissions only and the main priority should be on cutting emissions. Giki Zero therefore includes trees but removals are shown separately from emissions rather than netting the two off.

Tree planting footprint

Tree carbon footprints are calculated for a person based on the number of trees planted (average, estimated) multiplied by the amount of carbon each tree sequesters over a given time period.

The average is zero trees so any non-zero footprint result comes from a person entering trees they have planted in a given year. Tree carbon sequestration is calculated cumulatively using US Department of Energy Information looking at the average of slow, medium and fast growing conifers and hardwoods adjusting for survival rates over a period of time and multiplying carbon sequestered by the carbon / carbon dioxide equivalence ratio. The time period runs from the current date until 2025 and all numbers are negative.

Sources

Additional Model specifications

  • Tree footprints are calculated for an individual.

Forest conservation footprint

Forest conservation footprints are calculated for a person based on the numbers of acres of rainforest protected (average, actual) multiplied by the amount of carbon saved by avoiding deforestation.

The average is zero so any non-zero footprint results comes from a person entering the acres they have protected in a given year. Carbon emissions avoided are calculated using a range of sources looking at different types of rainforest taking the mid point of estimates. Estimates are for a single time period only, i.e. more forests must be protected each time period in order to maintain the estimate.

Sources

Additional Model specifications

  • Forest conservation footprints are calculated for an individual.

Giki Score

The Giki score provides a single metric for individuals to keep track of everything they are doing for the planet. It is calculated as an inverse function of an individual’s overall carbon footprint with additional points for committed steps, completed steps and footprints completed. A individual’s carbon footprint is the most heavily weighted component of the score such that a high score, and in particular a score above 1000 which indicates that an individual has a carbon footprint that is aligned with a 1.5C lifestyle, can only be achieved with a low absolute carbon footprint.

score updates

March 2021 – score updated to limit the amount of additional points that can be accrued by using nature based offsets. Following research on the steps that people can take to lead a Paris aligned life (see https://giki.earth/reduce-replace-repair) the Giki score was updated to limit the amount of carbon sequestered that is included in the score to the amount necessary after reduce and replace actions are taken. This ensures that an individual with a high footprint cannot plant trees to get a high score whilst still having high absolute emissions.

December 2021 – models updated with new Defra conversion factors including for UK grid mix. EV car emissions from grid added to direct emissions and LCA emissions.

April 2022 – carbon footprints show with emissions and removals separately rather than netting off. As emissions continue to rise the focus need to be on cutting first.

Global Models

Global models are calculated as averages across high income countries typically the US, EU and UK. When the Global region has been selected users should enter actual data where possible to improve the estimation process. This is particularly relevant for Electricity and Gas footprints.

Demographic information

Demographic information comes from a variety of country and global sources including:

Achievements

Carbon, water, land and single use plastic achievements from trying and completed steps

The achievements section, which is included within Giki Zero Pro includes estimates of the carbon, land, water and single use plastic that may be avoided through either through committed, or completed action. Calculations for all savings are based on global averages, for high income countries, rather than the specific inputs of an individual user model or region over a period which is most typically a year.

As an example the savings for renewable electricity are calculated based on average electricity consumption with typical global grid conversion factors and the savings for reducing flying are based on average numbers of flights taken. For some people this will lead to an underestimation of potential savings (for example for a frequent flier) and for others an overestimation (for example someone who lives in a household with higher than global average electricity usage). In a similar way carbon, water, land and single use plastic avoided is not typically assumed beyond one year. This may potentially underestimate the lifetime value of a change but also reflects the evolving nature of habits.

As such achievements are useful as indicative carbon, water, land and single use plastic avoided by committed or completed steps but the primary goal of Giki Zero is to commit to, and complete, steps and to reduce carbon footprints which can be updated in the footprints section for an individual. Single use plastic is not calculated elsewhere in Giki Zero and is based on global averages, for high income countries. Each item is considered separately e.g food packaging may have multiple single use components.

Comparisons

Where comparisons, or “fun comps” are provided to clients these are calculated by comparing the achievements from trying and completed steps to a number of items including miles driven, homes powered and showers saved. These are provided for illustrative purposes to encourage behaviour change and to provide context for users about the impact of their actions.

Refinements

An individual can use average, estimated or actual data in Giki Zero’s Footprint models. In some cases estimates are taken from initial proxies (e.g. house electricity usage can be calculated looking at house size and house type) and then further refined by looking at other adjustments which may affect usage. For example in the case of electricity this includes whether an individual is using a green electricity tariff, whether they turn lights off and whether they limit the use of a tumble drier. Each refinement is individually researched to give an estimate of the impact it will have.

However, for individuals who want a more personalised estimate they should enter actual information which will provide a better estimation process since it will reflect the actual quantities consumed.

Taking electricity as an example again the total kWh consumed in a year will naturally provide a more precise carbon footprint that the estimation process almost irrespective of the number of additional estimation factors that are included.