 This question's from Randy. How long do tankless water heaters typically last? If you take care of your tankless water heater and do the regular maintenance recommended by your manufacturer, it should last you about 20 years. This is two or three times longer than a tank type heater. The one we installed is called the Bosch Green Therm 9000 and we love that it comes with a 15 year warranty on the heat exchanger. Here's some advice though. You really should get your water tested if you have water using appliances. Scale can do a lot of damage to those systems. We also ask Connecticut to do water tests on all of our projects.