Many solar companies guarantee production. What does a solar production warranty mean and how does it protect you?
There are two kinds of guarantees that involve system production on a solar array.
The manufacturer of the solar panels guarantees production over time with a Power Output Warranty. That warranty ensures your solar system will perform within the set degradation rate on the cells in the panels for the life of the system.
This is listed on the specification sheet as a percentage per year (.5%, .3% or .25% are common) and an “at least” percentage at year 25 (88%, 89%, 90% etc.) The lower the first number is, the higher the 2nd number is. Look for the highest percentage at year 25 number. As long as you select a system with a year 25 “at least” number of 89% or better, you’re fine on this parameter.
The 2nd kind of production guarantee is from the system installer, leasing company (SunRun, Tesla, Sunnova, etc.) or sales organization (Powur, Vir, Freedom Forever, etc.). This type of warranty guarantees a specific number of kilowatt hours will be produced per year by the system.
Remember, your goal is to match supply (kWh from solar) to demand (the number of kWh you use/will use annually. Make sure you understand what your demand is. Get your NV Energy bill and add up how many kilowatt hours you used over the last 12 months to get an annual total. Production on the proposed system should be within 500 kWh of your annual load.)
Sometimes these warranties last for the first year. Sometimes they are longer. This type of warranty is ensuring your installer is putting panels in the most optimal place…not to close to roof vents or other sources of shade and correctly accounting for shade they cannot avoid (your neighbor’s 25 foot tall tree that you can’t trim for example) It is also protecting you from having the system be undersized because a sales representative was dishonest about expected production.
PRO TIP: Use a little logic here. Most of the popular panels these days are 300 to 360 watts…. so the “engines” that make the power are all roughly similar in generating capacity. But it’s not at all mathematically probable that (20) 330 watt panels would produce the same amount of power as (30) 360 watt panels. The lower the wattage of the panel is and the lower it’s efficiency is, the lower the total number of kWh that panel is going to create annually.