Theres a reason why the panels are oversized - its all about production efficiency.
To ensure that your system operates to the maximum efficiency, it is installed to Enphase guidelines.
Oversizing the panels to the inverters is a concept that has been exercised for a long time by many inverter manufacturers - Enphase Micro inverters thrive on it.
The concept is to ensure that your inverters reach maximum efficiency for as much of the year as possible. The phenomenon called "Panel Clipping" is designed to allow the inverter to saturate production as often as possible during the day, increasing the systems work rate and daily yield.
The result is a system that has a greater yearly yield than the comparable Traditional DC system.
To Back up this theory, Enphase have tested various panel to inverter size combinations in their labs. results of which are published in a white paper “Bigger is Better” available on the Enphase website or from your Metro Solar sales consultant.
Results show that the optimum ratio for panel to inverter sizing is 1:1.24 =
215 Watt inverters / 270 Watt Panels
250 Watt inverters / 310 Watt Panels
275 Watt Inverters / 345 Watt Panels
The new 4th Generation 72 Cell inverter is designed to work with the higher voltage outputs from large 72 Cell 300+ watt panels
Results from - Bigger is Better White Paper - Enphase Energy