Electricity generation converts primary energy into electrical output. Thermal plants use heat and a turbine-generator cycle. Hydro plants use moving water, wind turbines use aerodynamic torque and photovoltaic systems convert light directly. A useful comparison includes capacity, annual energy, capacity factor, ramping ability, fuel or resource availability, emissions, water use, land, cost and grid location.
The sections below cover generation methods, plant systems, economics and safety. Installed capacity is not the same as generated energy: actual output changes with maintenance, dispatch, fuel or resource conditions and operating limits. Grid operators must balance generation and demand continuously while maintaining frequency, voltage, reserves and transmission limits. Forecasting, flexible resources, storage, transmission and controls help integrate variable wind and solar output.
