Just like any other major purchase, most homeowners who go solar choose to finance their purchase with a loan from a bank or some other type of financial institution.
But with solar loan terms typically ranging anywhere between 8 and 20 years, an obvious question arises:
How long are the solar panels themselves going to last?
After all, nobody wants to be in a position where they have to keep paying off a loan long after the product it was used to finance has stopped working.
Well, the short answer here is homeowners who choose to finance their solar system with longer-term loans don't have to worry about their monthly payments outlasting their panels.
The expected lifetime of a solar panel is generally 25-30 years. In fact, most manufacturers even offer a 25-year performance warranty.
For a more precise understanding of how long you can expect your solar panels to last, let's dig a little deeper.
Solar vs. other tech
The first point here is that—barring extraordinary circumstances—solar panels don't "break down" in the same way that more conventional technology usually fails.
When your water heater or some other home appliance needs replacing, there's a good chance that some internal malfunction made it simply stop working altogether.
But solar energy is created entirely at the subatomic level. As such, there are no moving parts involved. That eliminates the ordinary wear and tear that's the culprit when most products malfunction.
As surprising as it may be, the upshot is that—strictly speaking—your solar panels will, for all practical purposes, NEVER stop working. No moving parts mean nothing to break—so, you can literally expect your solar panels to keep generating energy for a hundred years and more.
The problem is that, while solar panels are basically immune to total breakdowns, the amount of energy they produce does decrease over time in a process called "degradation."
Degradation
Thankfully, degradation occurs at a very slow rate. On average, the power output of a solar panel only decreases by a minuscule 1% each year.
Nonetheless, after enough time has passed, that minuscule 1% decrease in efficiency occurring each and every year will start to add up.
What causes degradation?
By far the biggest factor is seasonal fluctuations in temperature.
Like everything else in the physical world, solar panels imperceptibly expand when heated and contract when cooled.
When
it comes to solar panels, however, this seasonal back-and-forth creates micro-cracks that impede the subatomic processes required to generate
solar energy.
The upshot is that there's really no way to mitigate the gradual loss of efficiency—no matter what you do, your solar panels will be subject to a very slow process of degradation.
Thankfully, degradation rates are so gradual that manufacturers are able to guarantee production estimates over time.Performance warranties
Since solar panels are pretty much immune to complete breakdowns, a manufacturer's guarantee that only kicks in when they stop working altogether wouldn't be of much use.
That's why—in addition to product warranties—solar panel manufacturers typically also offer performance warranties that guarantee their panels will keep generating close to their intended output for some specified period of time.
Performance warranties typically run for 25 years, with the amount of production guaranteed decreasing by a fixed percentage each year—usually around 1%. Performance warranties of this type are called "linear."
Some manufacturers, however, offer what’s known as a "step" performance warranty, instead. That means that efficiency degradation is guaranteed to not exceed a certain level for an initial part of the warranty period and guaranteed to not exceed a slightly higher level for the rest.
A step warranty might, for example, guarantee that production goes no lower than 90% for the first 10 years and no lower than 80% for the remaining 15.