Can you use four smaller 80 W panels with a single Enphase inverter?

George,

If the Enphase inverter sees a PV string that matches its input requirements, it will work. A PV module is a string as well, it's just a string of cells. Three discrete modules will be harder to estimate as far as the output is concerned because of module mis-match.

Tech support at Enphase is the approach I always use.  You want them to approve so that you don't void the warrantee on your inverter.

Here's Enphase's Module Compatibility Calculator. 

Start there and then send them a e-mail with your prosed layout.

Good luck!

George,

This is a great question; in fact I didn't know answer but I called Enphase Energy and they've sent me some links and told me that I can make my own compatibility calculation in order to connect more than one module per micro-inverter if the modules are identical.

When I make the calculations for 3 modules connected in series; it looks like it would work. Your multiple-module array would have Voc: 65.7 V, Isc: 5A. Since, it is a high voltage array (108 cells in total), you might need to use Enphase M210-84. But, please re-run the calculation on your own.

There is also a "Module Rightsizing" white paper (pdf document), which outlines the specific factors considered when determining optimum module power rating. It also provides a comparison of energy harvest between a 216W and a 235W module in three different geographic locations. It demonstrates that with the best location, optimum tilt, and regular cleaning, a 235W module paired with a 190W microinverter lost 0.61% of the maximum potential energy harvest. I wonder how much energy loss your system would face, given that you are losing some in your string connections.

Please ask further questions if you have any.

Also, please share with us how it goes; I believe more people would like to see how the performance is effected in such conditions.