Microwave oven

A microwave oven is a kitchen appliance employing microwave radiation primarily to cook or heat food.

Efficiency

A microwave oven does not convert all electrical energy into microwaves. A typical consumer microwave oven could consume 1100 W, and deliver 700 W of microwave power. The remaining 400 W are dissipated as heat by components of the oven. The main source of energy loss is the magnetron tube which is much less than 100% efficient at generating microwave output from the power source. Lesser amounts of power are consumed by the oven lamp, AC power transformer losses, magnetron cooling fan, food turntable motor and control circuits. This waste heat does not end up in the food but is mostly expelled from the cooling vents on the oven and heats the air in the kitchen. See Electrical efficiency.

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Most of the actual microwave power will end up heating the food inside the oven, unless the microwave oven is loaded with a very small amount of absorbing food. In that case, the magnetron element will reabsorb the microwaves, which can lead to overheating and a fire risk.

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