Energy imported and exported to the NZEB is measured in terms of carbon emissions resulting from their generation and transmission. Quantity of emissions determine the quantity of energy to be produced for achieving net zero status. Carbon emissions are one of the more holistic metrics of measuring NZEBs where difference in raw energy fuel types and non-energy variables like pollution are reflected.

Carbon, sulfur oxides, and nitrogen oxides are counted as carbon emissions. Renewable sources like nuclear, hydro and wind are considered zero emission at generation.

Energy used, produced or purchased by the building is multiplied by emissions factors to derive emissions on demand and supply side. Quantity and type of emissions from different fuels vary and so does the emission factors.

Demand side energy emissions factors are based on emissions from generation at the source, storage, delivery and transmission. Factor for supply side energy, if produced off-site, is also based on both generation and transmission emissions. Emissions for energy generated on site should be based only on generation related emissions.

National average generation emission factor for utility supplied electricity in India is 0.89 kgCO2e/kWh. Average transmission emission factor is 0.30 kgCO2e/kWh. Sum of these two and the number of interest to calculating carbon emissions for NZEBs is the average end user electricity consumption emission factor – 1.19 kgCO2e/kWh.

Captive or non-utility power generation is frequently used for supplying energy in commercial buildings in urban areas. These run on diesel oil or natural gas, and there are no transmission related emissions to be added.