The total system costs include also the complete list of non-monetised externalities that are not mediated by the electricity grid and that affect a country’s wider economy and well-being beyond the electric power system itself. To the extent that such externalities are monetised and emitters are held responsible for their emissions, they can also be integrated into plant-level cost accounting. The 2010 edition of the Projected Costs of Generating Electricity (IEA/NEA, 2010) thus imputed a tax of USD 30 per tonne of C02 on the emissions of fossil-fuel based generators.