MWt

MWt stands for megawatt thermal, a unit of thermal power equal to one million watts of heat energy per second. It is commonly used in engineering and energy systems to express the heat output of boilers, cogeneration plants, district heating facilities, and nuclear or fossil-fuel reactors. MWt is not an SI base unit; it is a practical unit combining the watt with a metric prefix to indicate thermal power, and is often written as MWt or MWth.

MWt measures thermal power, in contrast to MWe, which measures electrical power. The two relate through efficiency: P_e = η × P_t, where P_e is electrical output, P_t is thermal input, and η is the overall conversion efficiency. Typical thermal-to-electrical efficiency for power plants is around 30–40%, so 1 MWe generally corresponds to roughly 2.5–3.3 MWt depending on design. Conversely, a plant rated at, for example, 3000–4000 MWt may produce about 900–1600 MWe.

Common applications include rating of nuclear reactors (which often list thermal power in the thousands of MWt), large boilers, district heating networks, and industrial process heat. Over one hour, 1 MWt delivers about 3.6 GJ of heat energy.

In summary, MWt is a standard unit for expressing heat production capacity and is widely used alongside MWe to describe the performance of energy systems. Variants such as MWth are used interchangeably in many contexts.