Should you worry about clipping?

Clipping is a poplar term in the solar industry used to describe when the solar panel is producing more power at a given point in time versus what the inverter can convert from DC to AC electricity, resulting in a loss or power because of the inverter bottlenecking the flow. Clipping can happen with a centralized system and with micro-inverters. 

This page is meant to describe what clipping is, but more so to explain why clipping, especially with Enphase micro-inverters, is nothing to worry about. As someone who's been consulting and selling solar systems to homeowners directly over the last several years, I have come to be very familiar with what other solar salesman tell prospective customers when trying to sell them on a certain product they are using. One of the most BOGUS tactics I see is when salespeople are speaking negatively about micro-inverters because they are not rated to convert what the panel is producing and that ultimately means that if they were to use a centralized inverter instead that it would result in significant power gains even if the system is the same size. This is at best an outdated argument. 

Firstly, it is important to understand STC (standard test condition ratings), and NMOT (Nominal Module Operating Temperature ratings). The watt rating you see as advertised is the STC rating. This is essentially when the panel is in an ideal scenario which is NEVER on the roof. Depending on which panel you have, your average 400w panel (STC rating)  will only have a real world output of around 275-325w which is closer to its NMOT rating. 

The most popular Enphase micro-inverter models are the IQ8PLUS, IQ8M, and IQ8A. These micro inverters can output 295, 320, and 350w. On the surface, if you don't understand that the panel is not actually producing 400w, you'd think the micro wasn't sized correctly, but when you realize a 400w panel is actually a lot closer to 300w, clipping clearly becomes a nonissue since very little power is actually being lost.  It is oftentimes not even necessary to pair the IQ8A with a 400w panel because the IQ8M's simulation figures are almost the same depending on azimuth. 

The picture above shows a production graph with an kW output limit causing the production line to flatten in the middle of the day. If the components are paired correctly, this will be insignificant. It is also important to not that clipping can happen just as easily with a centralized inverting system if the inverter to panels ratio is too different as well. Putting 10kW of panels on a 7.5kW inverter is the same concept as pairing a 400w panel with a 300w rated micro-inverter. 

Julian Todd-Borden

(760) 473-5878

Superior Solar Consulting LLC