Knowing if your solar hot water heater is broken essentially comes down to leaks and whether you are getting enough hot water at the right temperature. While there are many different types of solar water heaters used in different climates the above statement will hold true for all of them.
Leaks in a solar hot water heater can show up in a couple of ways. The most obvious is water visibly running from a leak. In some systems a leak in a collector may not show as water running down the roof but instead as a fogging of steam on the collector plate.
Solar water heating systems today involve getting heat for the water from the sun, storing it for use later, and backup heating in the event there is not enough sun heated water to meet your needs. Also systems in colder climates there are additional things such as drain back and possibly an anti-freeze loop that involves extra controls and parts. These systems are pretty reliable and don’t often require service but owners of these systems should have a basic understanding of how their installed unit operates and be able to recognize when something isn’t operating correctly. Typically the first symptoms will involve not enough hot water being delivered. System owners should be able to realize when this is caused by a usage spike during a time of low solar heating and a malfunctioning system so they know when to call for service.