Figure 5. Schematic diagram for carbon emission flow in a power grid.

Using the angle of carbon emission flow, carbon emission is no longer emitted from the source node. The emissions travel along transmission paths with energy flow to consumers, as if CO₂ is emitted by consumers through the network. When consumers use energy, they accumulate carbon emission flow as well. The accumulation of carbon emission flow can be calculated using a proper method and is regarded as carbon cost.