Does an inverter have 25 year life times?

The effect of shading on solar panels, and what this would do to a string inverter vs. micro-inverter, is much misunderstood. Even by experienced installers. All grid-tie modules I've seen in the past few years have bypass diodes, dividing the panel up in 3 segments.

Do not confuse warranty with longevity: A 25-year warranty does not mean that the manufacturer expects the inverters to live (at least) 25 years life. It means that most will live that long, some will fail early, the micro-inverter is dirt cheap to make, and you paid enough for it so the manufacturer can afford those warranty replacement while still making a buck. As for Gozuk, they have had massive numbers of their inverters fail early (they claim that has been remedied in the design of their latest products). While they pay $175 to replace an inverter, it costs a heck of a lot more when they are roof mounted, and I have to pull panels to get to that broken inverter.

We'll put micro-inverters up if the customer wants it, though I'll try to talk them out of it. I can guarantee, not that there's a slight chance, but guarantee, that if you put 40+ micro-inverters up on a roof at least one will fail over a 20-year life time-period (the duration of our FIT contracts here in Ontario). Love their monitoring though!

There's rarely a situation where micro-inverters are really needed, including cases with shading, and they will bring additional revenue for the customer. 95% of cases (possibly more) we can set things up so shading will have the same effect in production with a string inverter (in particular with the power one inverters since we can divide things over two MPPT inputs per inverter, so for a 10kW system we have 4 MPPT inputs to work with and rarely need to parallel strings). About the only situation where micro-inverters or optimizers are a must is if we have 3 or more roof surfaces with different orientation/pitch, so those panels would run at different MPPT points.

In terms of cost, we charge an extra $0.50/Watt for Gozuk, and that pretty much just covers our additional cost, there's no additional profit on that. For a 10kW install it makes quite a difference in price for the customer.