Microwaves last 7–10 years. Over-range microwaves have shorter lifespans than countertop units due to heat exposure from the stovetop below.
Microwaves have a shorter lifespan than most major appliances — NAHB data shows an average of 9 years, with a 7–10 year range. Over-the-range microwaves tend toward the lower end because they endure heat and grease vapor from the cooktop below, while countertop models are more protected. The magnetron tube is the heart of the microwave and the most expensive component to replace; when it fails on an older unit, replacement is almost always the better economic choice. Control board failures and door switch problems are more common and easier to repair.
Replace your microwave when the magnetron fails (magnetron replacement typically costs $150–$250 in parts alone, making it uneconomical on any unit over 5 years old), or when multiple door switches fail simultaneously. Turntable motor replacement ($20–$40) and control panel replacements on units under 7 years old are worth considering. If sparking occurs, stop using the microwave immediately until inspected.
The waveguide cover is a small mica or cardboard sheet on the interior wall of the microwave that most people don't know exists — and which causes the majority of "sparking microwave" calls. When it gets food splattered on it and is never cleaned, it burns and causes arcing. Replacement costs about $10–$15 and takes 2 minutes. Clean or replace it before concluding the microwave is broken.
The most common cause is a dirty or burned waveguide cover — the mica or cardboard panel inside the microwave cavity. Food residue on it causes electrical arcing. Replace it ($10–$15) before assuming the microwave needs major repair. Metal accidentally inside the microwave is the other common cause.
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