megawatt

The megawatt is the unit of big machinery and of the grid. A modern freight locomotive delivers about 3 MW at the rail, the largest offshore wind turbines are rated near 15 MW, a single gas turbine unit runs to several hundred, and a large nuclear reactor's electrical output sits near 1000. Grid operators balance supply against demand in megawatts minute by minute, and the newest data centre campuses request connections of 100 MW and more, which is why electricity availability has begun to decide where computing gets built.

The most powerful reciprocating engine ever built is rated in this unit. The Wärtsilä RT-flex96C, a fourteen-cylinder marine two-stroke diesel that drives the largest container ships, produces about 80 MW from a single crankshaft, the output of roughly 25 locomotives. Ship propulsion is where piston engines reach their ceiling; above that scale, everything that turns a shaft is a turbine.

Beyond the MW-versus-MWh trap in the caution, keep capacity factor in view. A 15 MW turbine does not deliver 15 MW on average: over a year an offshore machine typically produces 40 to 50 percent of its nameplate energy, a solar farm 15 to 25 percent depending on latitude. Nameplate megawatts times 8760 hours gives the annual energy ceiling, and the fraction of that ceiling actually achieved is the single most informative number about any generator.