In addition to standard solar product warranty, there are several types of warranties that can be purchased or come with a PV system, including: (1) Solar system warranties which will cover proper operation of solar equipment for a specific time of period, (2) Solar product warranty which covers defects in manufacture, for example: Enphase micro inverter manufacturer provides 25yrs product warranty. (3) Energy performance / output warranty covering the output of solar system on annual basis. Most solar EPC contractors which provides solar system installation workmanship warranty, will often overs system and annual power performance warranties.

First of all: Understanding solar system warranties:

To review entire system-level warranties of 10yrs or more is equally importance comparing with 10yrs product warranty.

This indicates that the solar product manufacturer has taken many other operational issues into account. Since solar PV systems generate electrical power (DC or AC), it is critical to have system performance included as part of the warranty.

For example, a typical system level warranty might state that the system is guaranteed to produce two kilowatts (2 kW) of  AC power at Test Conditions (PTC) (PTC is 1kW/m2 irradiance, 1 m/s wind speed, 20oC ambient temperature) in the fifth year of operation. The equipment to perform this test is expensive, but the fact that a company would know enough to specify this type of warranty is an indication that they are confident in their system design. The California Energy Commission Buy down program requires installing contractor to provide these warranties. The intent of this requirement is to improve customer acceptance of PV systems.

Second: Get familiar with standard product warranties:

Most solar panel manufacturers provide 25yrs standard warranties. However, there are many other solar related components in the whole system that may or may not have same 25yrs life expectancy, although this is impressive and indicates the level of confidence manufacturers place.

Micro inverter may have 25yrs warranty, string inverter will have standard 10yrs warranties and some optimizer manufacturers will provide 12yrs warranty on certain parts. This must be considered when reviewing the cost of inverters and other system components.

Third: Pay attention to annual performance & power production/output warranties:

Energy performance warranty will guaranty that the whole solar system will perform consistently over certain period of time, for example: 25yrs. However, there are very few companies selling system with Energy performance warranty, unless seller owns system, such as solar product leasing company. This is particularly helpful in ensuring that the customer receives the bill savings that they expect.

Energy performance warranty is more common with energy efficiency retrofit projects for commercial and industrial clients. Adequate metering to verify the system power output and energy generation is necessary to help the system owner understand whether the system is operating properly, or has warranty-related performance issues. With an adequate meter, the customer can readily identify when the system is malfunctioning.