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10 minutes daily


1 700

kg CO2e


Click the expendable headlines to look at each step of the calculation. 

To calculate the greenhouse gas emissions of heating an apartment using district heating from a plant burning fossil gas, we have used the following data:

  • Heating system: district heating plant burning fossil gas
  • Heating demand of the apartment: 468 MJ per square meter and year
  • Living area: 50 square meters
  • Emissions from combustion of fossil gas: 63.5 g CO2e per MJ
  • Conversion efficiency of the boiler: 85% (representative value of large-scale gas boilers)

The thermal energy required to heat the apartment for one year is calculated by multiplying the living space by the heating demand per square meter and year.

50 m2 × 468 MJ per m2 and year = 23 400 MJ per year

The calculation shows that the energy demand amounts to 23 400 MJ per year. This corresponds to the amount of heat that needs to be supplied via the district heating system.

The conversion efficiency is a measure that indicates how effectively a boiler converts the energy contained in the fuel into usable heat. A gas boiler with an efficiency of 85% means that 85% of the energy contained in the gas is converted into useful energy (the remaining 15% is lost, or “not useful”). The actual energy demand is calculated by dividing the thermal energy demand by the conversion efficiency. 

23 400 MJ per year / 0.85 = 27 529 MJ per year

The calculation shows that the actual energy demand amounts to 27 529 MJ per year.

The greenhouse gas emissions are calculated by multiplying the total heat demand by the emission factor for combustion of fossil gas.

27 529 MJ per year × 63.5 g CO2e per MJ ≈ 1 748 kg CO2e per year

The calculation shows that the emissions amount to 1 748 kg CO2e, which has been rounded to 1 700 kg CO2e on the card.

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