A method operates a power converter that contains power converter arms. Each of the power converter arms has switching modules and each of the switching modules has a plurality of semiconductor switches and an energy store. A temperature value for the power converter is ascertained on the basis of a state model of the power converter, wherein the ascertainment is repeated so as to obtain time-related temperature values. A number and a magnitude of temperature swings that have occurred are ascertained from the temperature values, and a remaining service life for the power converter is estimated based on the ascertained number and magnitude. A power converter is configured to carry out the above-described method.