Here's a quick follow-up to the entry I wrote about micro-inverters two days ago. First, I should clarify that Enphase Energy's micro-inverters have a projected lifetime of 25 years, not 119 years. Of course 25 years is considerably longer than the 10- to 15-year projected lifetime for traditional inverters.

Second, Enphase Energy responded very quickly to an e-mail inquiry I sent to them. It helps to further clarify some of the potential benefits of a micro-inverter based system. So, I've pasted it below -->

"When comparing cost between a central inverter and a micro-inverter this comparison is always dependent on system size. In some cases a micro-inverter is less expensive on a $/W basis and in other cases it may cost more.

The important point is that there are more items to compare than the cost of inverter hardware when looking at a comparison between the two. There are significant savings to system design and installation when using a micro-inverter system. For example there is no string sizing necessary, there is almost no DC cabling, no combiner boxes, no DC disconnects, and if a roof penetration is done then there is almost no conduit.

When comparing $/W between the two systems the costs of these components and their installation should be considered as a part of the cost of a central inverter system.

Of equal importance is the comparison of energy harvest over the life of the system between the two types of inverter architecture. With an Enphase micro-inverter system there are significant advantages to the systems productivity because of MPPT on every module in the system.

Additionally there are advantages to system reliability/uptime as well as inverter reliability. And further advantages in regards to monitoring and safety. In short, while a cost comparison of the two will prove comparable on a $/W basis it is difficult to compare the two systems without considering many other factors toward installation and expected productivity."