First, accounting for environmental externalities (“air pollution”, mainly of S02, NOx and PM2.5, “climate externalities" in the form of GHG emissions and “other costs”, including radioactivity) significantly alters the cost comparison across different technologies, especially for coal-based generation. Second, solar- and wind-based generation (and to a lesser extent nuclear) are characterized by relatively high capital expenditure, with negligible marginal operating costs. Third, unlike fully controllable technologies, variable renewable technologies have positive system costs, reflecting the need to balance their variable temporal profile and enhance grid flexibility. These costs increase with the unpredictability of the energy source, so are higher for wind than for solar.