Electricity is a secondary energy source, meaning that it is produced by converting primary energy sources — renewables such as solar, wind or geothermal energy; or non-renewable such as coal, gas or oil. In cities electricity is mostly produced in large power plants (often outside city boundaries), although local electricity production (with renewables, most notably from solar panels) is increasing fast.

Emissions from electric power are dependent on the production mix in the grid — often ranging across nations (e.g. internal European electricity market), leaving a city with limited scope to influence the emissions coming from grid electricity.