The national average for water heater repair is $585. The average cost of most repairs is between $218 and $953, although homeowners have paid as little as $100 and as much as $1,300. A blown pilot light, a tripped circuit breaker or a damaged thermostat are all examples of potential issues. The cost of replacing a thermostat is between $100 and $300 on average. The majority of other water heater repairs are also reasonably priced.