Ever wonder why we pair M215 microinverters with 285W solar modules? At first glance it may seem like there is the potential for lost sun rays, but actually the combination results in substantial gains in annual production with minimal losses to inverter saturation — and it’s the most cost-effective pairing when comparing cost versus value of larger microinverters.
Need a full explanation?
Recent studies by Enphase Energy found that using larger module sizes significantly improves annual energy production, even while inverter size remains unchanged. By applying high power solar modules to microinverters you will gain greater lifetime performance, lower installed cost per watt, and ultimately, the highest return on your investment. However, increasing the microinverter size increases the system cost with little effect on increased system production.
Losses incurred from inverter saturation (this happens when the solar module produces more than the inverter's maximum of 225W) are negligible because microinverters spend very little time in saturation. The reason for this is that a solar module very rarely produces its rated power due to losses from heat. The rating comes from tests done at "STC" or Standard Test Conditions of 1000W/m2 solar irradiance and 25 degrees C (77 degrees F). Those conditions are certainly reasonable for a warm sunny day in Portland, but when you consider that a solar cell is roughly 19% efficient, the other 81% of 1000W/m2 gets turned into heat! When temperatures go up, voltage (and thus power) go down. Before you get discouraged, rest assured that this is all taken into account when predicting your system's annual production. When tested by Enphase, annual losses to inverter saturation were insignificant. In 90% of the scenarios using the M215 Microinverter, annual losses were less than 0.5%!
In the figure above, you can see that the 285W solar module is almost approaching the point where it would be an even trade-off. However, even if it were to reach that point, we would likely recommend chosing the M215's because they have proven to be a high-quality product with low failure rate. While the M250's may also live up to that same quality standard, it would take 30 additional years to reap the full benefits of its capacity from an investment when compared to the shorter ROI of the M215s.
It is evident from both the Enphase study and our own monitoring of Elemental Energy installed solar systems throughout Oregon, that pairing high power solar modules (such as the 285W) with the M215 microinverter results in substantial gains in annual production, minimal losses to inverter saturation, and your largest return on investment!