On leases or PPAs (power production agreement).

The panels get less efficient as the system ages, but every year the monthly contract price goes up even though every month you produce slightly less power. This is called panel degradation. I think the inverter also loses efficiency but not as marked.

As soon as you sign the lease, the contract is likely to be sold to a third party. In my experience from a practical and legal standpoint, these companies have very little incentive to maintain systems or work with home owners if something major happens like a tree falls on the panels/roof or if the roof otherwise needs replacement.

The companies advertise no cost of maintenance as you pointed out but you still owe money for the power the panels would have produced even if they stop producing for reasons outside of your control.

So if you get a tree branch through your system, they have no reason to rush to remove the panels so a roofer can come in (you're not allowed to remove the panels) because you still owe them the same amount of money each month regardless of whether the system is functioning. Instead of paying for what you actually produced, you owe for what you should have produced.

They also advertise no cost removal of the panels if you want to end the lease and that is true but you still owe monthly payments for the entire lease duration, which could be twenty plus years. They just don't charge a separate line item to remove a system (why would they, since they can lease it to someone else).

Just thought I'd add some detail because I hate leases so much.