Inverter capacity plays role in panel capacity as well, according to EIA
A report from the U.S. Energy Information Administration (EIA) has found that solar plants are following what is known as the inverter loading ratio (ILR) and are installing more panel capacity based on their inverter capacity.
This whole concept revolves around the fact that the nation’s solar system is typically split into two different figure trackings for its panel capacity and operating capacity. Panel capacity tends to be reported in direct current (DC) while operating capacity–what is being delivered to the grid–revolves around alternating current (AC). Capacity values reported in DC, though, are usually 10 to 30 percent higher than those in AC, which accounts for the ILR.
As of 2016, the United States was producing 20.3 gigawatt AC for its large-scale photovoltaic (PV) capacity in operation, against a DC module rating of 25.4 GW. The ILR clocked in at 1.25 as a result. Solar panels may only reach peak DC capacity a few times a year, though, and the outputs fluctuate regularly. So the EIA determined that solar PV facilities intentionally over-build the DC capacity, as it may not be cost-effective to size an AC inverter to capture at full output. Likewise, solar output declines naturally over time, because PV cell and module performance degrades.
Thus, the larger the solar power plant, the larger the inverter loading ratio becomes. As of 2016, the EIA reports that smaller plants had only an average ILR of 1.17, while larger plants reached 1.30, and as solar plants increase in size, their ILRs are going up with them.
