When I tell people that I have been in the solar industry for over 9 years. They start asking me questions. The most common question I get asked is:
How long is the payback period if I put solar on my home or commercial business?
And I say, it depends. On many factors. In a place like Hawaii where electricity is 3x more expensive than the average state and sun is plenty, your payback period might be 1-2 years. In California, where electricity is 1-2x more expensive than the average, it might be 3-5 years.
In other places it could be 5-6-7 years or even 8-12 depending on the local electricity price, local state and city incentives, and the amount of sun (in that order of importance).
The second most common question I get is:
How many years will the solar panels work for?
And the answer for that question is: 30+ years. At this point almost all solar panels come with 25 or 30 years warranties. And most panels will last up to 40 years. Panel do suffer from degradation at the rate of about 0.5% or less per year. So after 20 years, a panel will likely produce 80-85% of the energy it produced in its 1st year.
I have had conversations with veteran solar pros who have installed panels 35+ years ago and they say their panels are still producing at 75% plus of their first year production.