Solar PV panels come with two warranties, a Performance Warranty and a Product Warranty.
The Performance Warranty will guarantee the maximum drop in efficiency of the panel over a 20 or 25 year period. Commonly this is stated as a percentage figure that the panel is guaranteed to produce at given points in the lifetime of the panel. Most quality panels will provide a guarantee that the performance will not drop below 80% of its original efficiency at the end of the given period.
Although the life expectancy of a solar PV panel is to be expected to be more than 20 years, product warranties for the physical construction of a PV module are generally for 10 to 12 years.
The efficiency of string inverters reduces over time and have a life span of 10 to 15 years. This is shorter than that of the panels, so will be necessary to replace a string inverter to maintain the overall output of an array.
Micro-inverters and optimisers have a longer life expectancy as the electrical load passing through them is less than for a string inverter.