It's likely worthwhile to repair your microwave rather than replace it if you have a high-end built-in appliance or if the repairs cost less than a new replacement. It's best to research the cost of an appliance installation before making a decision. However, if your appliance is over 10 years old, it's better to invest in a brand-new machine since it's already nearing the end of its life span. If you decide to buy a new microwave, consider getting appliance refinishing projects done at the same time to give your kitchen look a refresh.