I am a big fan of micro-inverters

You are correct about correctly pairing a module with a micro inverter. You are also correct that on string inverters there is a bigger range of usable module sizes than with the said Gozuk for example. But you are talking about pairing a module type with an inverter type, I wasn't referring this kind of "Mismatch"...

I am referring to an effect that occurs with string inverters which can affect the inverter's performance.

I'm sure you are familiar with what is called the I V curve for modules for those who aren't I'll summarize:

• at each instant the modules operates at a certain current I and Voltage V
• The Maximum Power Point Tracking (MPPT) algorithms in inverters constantly track the best point on that IV curve to optimize the power output.

At Best, string inverters will have MPPT at the string level and sometimes multiple strings are connected to 1 MPPT.

You also are aware that modules that come out of the factory are not perfectly identical, therefore even if "you know what you're doing" you will have strings with slightly different electrical properties and, within the strings, modules with slightly different IV curves. The reasons for such variations may come from the following reasons:

• intrinsic manufacturing differences
• slight variation in orientation and inclination during installation (uneven rails or surfaces etc...)
• partial shading
• etc...

To summarize, even if you are the most experienced and precise designer / installer in the world, "identical" modules will have variations in their IV curves under specific irradiation conditions.

These variations in IV curves have a direct effect on the efficiency of the MPPT algorithm.

A micro inverter avoids all this strings issues and under the same irradiation, a micro-inverter based system will always produce more kWh per kWp installed.

Now, I am a big fan of micro-inverters but until certain improvements occur, there will still be many projects (mostly large ones) where string inverters remain the best option.

Indeed, there are other factors than kWh / kWp that are involved in evaluating a project, namely:

surface constraints, BOS costs, inverter and modules cost etc...

Each project must be analyzed with a total life cycle cost approach to determine the best option. At the moment we are observing that due to the extra energy production, micro-inverter based systems make the most sense for us in small to medium scale Commercial installations.