The performance of a microwave gets worse gradually: a microwave loses
power from day one.
So we can't say that there is a sudden moment after which a microwave
has a lot less power:
"Microwave ovens of any price easily should last 10 years or more,"
says Swamy Anantheswaran, associate professor of food science. "But
there will be changes in performance -- usually a decline in power so
gradual that consumers never notice it."
Anantheswaran explains that the magnetron, the electrical element that
converts electrical energy into microwave energy, will not maintain
the same power levels over time. "If a new microwave oven boils a cup
of water in one minute, after five or 10 years it may take 90
seconds," Anantheswaran says.
Although microwave ovens lose power as they age, Anantheswaran says
most consumers unconsciously adjust cooking times without realizing
the oven is not performing as efficiently.
Source: "Microwave overns can be zapped by age factors"
Google: +microwave +"lose power" +older
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