Calculation of footprint for energy

Calculate a personal energy footprint from household information and habits. This can be used to put energy footprints in context and nudge users towards more sustainable energy use.

Inputs

This endpoint receives as optional input:

• a data source to base calculations on
• a list of energy habits and a household description
  • Number of household members
  • Size of dwelling
  • Type of dwelling (e.g. detached house, row house or apartment)
  • The renovation level. This influences the degree of insulation and thereby the heating requirement
  • How large a portion of the dwelling is heated. This modifies the total heating energy by the percentage of area
  • Typical indoor temperature. Higher temperature means the heater would need to do more work which equates to more emissions!
  • Primary energy source (one of three types of heat pumps, electric heaters, district heating, oil or gas)
  • How much wood you use for heating (if any) in cubic metres
  • Type of shower, shower frequency and shower length (together determine hot water usage)
  • Percentage of lights that have LED bulbs, how often you turn off the lights and whether you unplug devices on standby.
  • How often you save water, do dishes, and tumble dry
  • Electricity generated through installed solar panels (in kWh)
  • Size of cabin (if any)
• the date for which the footprint should be computed

The more questions a user answers the better we understand the user’s behaviour, giving a more accurate footprint estimation. All inputs are optional and missing values are defaulted. If no input date is given, the current date is used as default. If no habits are provided the calculation will assume default answers, i.e. that the user’s energy habits and household are similar to an average person from the data source you have specified. This can be used to compare a person's energy footprint to the average person in a country.

Outputs

This endpoint returns a breakdown of an annual energy footprint in kilos of CO2e, with absolute and percentage values. 

The energy footprint can be aggregated as per energy source (electricity, gas, district heating, wood) or purpose (heating, lighting, hot water and appliances), depending on the user’s preference.

If you have not submitted optional information, the footprint of an average person for the chosen data source will be returned.

Calculations

Size and type of housing

The basis for calculating the energy used in a household is the size and type of house. Using Statistics Norway’s energy consumption per m2, BEIS Department’s Energy Consumption in the UK and other sources, we calculate an estimate of a household’s energy use for different dwelling types.

The energy use in a house varies based on the type of house, the number of people living there, and the year the house was built and last renovated. A row house built in 2012 with two people living inside it is likely to use much less energy than a family of six living in a large standalone house built in 1917.

We have energy use per area for different house types and number of persons in the household. This is used to adjust the total energy use for the household with the number of people living in the household. Additionally, Sandberg et al. (2016) give energy use per dwelling type, renovation standard and construction year. So the more input given about your house, the more accurate the calculations become.

Energy use breakdown

The footprint calculation breaks the total energy use into several subcategories. The fraction of the total energy used for the purposes of heating, lighting, and other/appliances are calculated from the total energy using a breakdown of energy use, provided by the Norwegian Energy Regulatory Authority for Norway and Department for Business, Energy and Industry Strategy for the UK. 

Water heating

The energy used for heating water is calculated bottom-up from the household inputs on hot water use, by multiplying the water used for showering with the showering length, frequency and number of household members. Hot water for other purposes than showering is also added. Total hot water use is converted to energy using the average energy needed to heat water from 10 to 38°C. 

Heating

To calculate energy used for heating, the heating energy use estimated from the total energy use is adjusted using correction factors. Input data for the renovation level, area of the house that is heated, and indoor temperature preferences are added to the calculations in order to get a more accurate estimation of the heating needs of a house. The energy  needed for heating is divided by the number of household members, and the energy obtained from burning wood is subtracted. The remaining kWh are multiplied with the multiplier for the primary heat source (multipliers as described in the convert energy article).

Lighting

For lighting energy use, we take the average amount of energy used for lighting and couple it with correction factors associated with household size. If users turn off unnecessary lights or use LED lights in their home, we take this into consideration in our calculations and lower the energy use accordingly.

Electronics and appliances

For appliances and other electronics, the average energy use is also adjusted based on user input. Dishwashers and tumble dryers use large amounts of energy, so if you use a clothes horse or wash less dishes than average, energy use is reduced accordingly.

Solar panels

If you have solar panels installed in your home, we subtract the electricity generated using solar panels from the total electricity consumption. To calculate the emissions from the remaining electricity use, we use the average emissions intensity of European electricity production. The savings in emissions due to solar panels is capped  i.e we do not account for the excess electricity that your panels might feed back into the grid. For example if you have solar panels which produce more electricity than you consume, the CO2e savings are calculated using the amount of electricity you consume, and not the amount you produce. 

Cabin

We also consider the emissions from the energy use in your cabin. If you have a cabin, you are asked to input its area. We have calculated a factor for energy use per square meter (kWh/m2)  for an average cabin. This factor is multiplied with the cabin area to get the energy use, which is then combined  with the energy factor to get the corresponding emissions.

Input date

The date also influences the calculations. We account for technology changes over time (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. The average emissions intensity of the European energy grid has decreased in the last decade and will continue to do so in the future. So, if we wanted to look at our energy footprint five years ago, it would be higher than the current energy footprint (keeping the energy use constant).