Like any investment in home improvement, homeowners looking to purchase solar panels care about longevity, as they should. After all, solar panels are electric, so like any appliance that runs off electricity, it is optimally functional for a certain period of time before it starts to suffer, performance-wise. Much like a dishwasher, you want the solar panels you purchase to work at maximum efficiency for as long as possible to maximize your investment. That's why when comparing panels, the useful life of a panel is a major factor you should consider.
Useful Life, as defined by SunPower, is how long 99 out of 100 panels will operate at more than 70% of rated power. In other words, once your system degrades such that most of or all of your panels are producing 70% of their original capacity, your system has gone beyond its useful life. Conventional solar panels' typically have a minimum peak power (guaranteed power) rating of around 85% in 25 years, while SunPower's warranty boasts 92%.
A recent study of SunPower panels indicates that they have a useful life of over 40 years. With degradation rates of under no more than .25% per year, SunPower panels have been found to produce not only more power in the first 25 years but continued to produce at over 80% efficiency even into year 40. That's another 15 years of production, even after your warranty expires.
Why is Useful Life important?
You get more value from your system: With a longer useful life, you'll be saving on your electric bill for much longer. That can equal out to huge savings, and therefore, provides more value as an investment. With this reliability and longevity, you can also estimate your ROI better over time.
Your home resale value will be higher: If you plan on selling your home in the future, panels that are high functioning and produce more electricity will add more value to your sale than panels that aren't functioning properly. A recent U.S.government study found that solar homes sold for approximately $5,500/kW more than non-solar homes. This obviously hinges on the performance of the panels, so having that reliable useful life will ensure you'll get the maximum amount for your home sale, taking the solar into account.
So when you choose a panel company you should know what the useful life is, as many companies have more than 70% degradation after 25 years.
Fortunately, homeowners who go with SunPower can rest easy knowing their panels are going to produce 80% or more of their rated power for over 40 years.