The only power generating component of the system is the PV array (the modules, also known as the DC power). For example a 9 kW DC PV array is rated to have the capacity to produce 9 kW of po.
Higher DC:AC ratios always improve inverter utilization and the capacity factor. The measurement of inverter utilization is capacity factor—the ratio between actual and maximum energy production. A significant portion of system cost is tied to the AC rating of the inverter (string or microinverter).
What happens if DC/AC ratio is too high?
When the DC/AC ratio of a solar system is too high, the likelihood of the PV array producing more power than the inverter can handle is increases. In the event that the PV array outputs more energy than the inverter can handle, the inverter will reduce the voltage of the electricity and drop the power output.
Do Enphase microinverters have a DC/AC Ratio limit?
Enphase Microinverters have no DC:AC ratio input limit aside from DC input voltage and current compatibility. Higher DC:AC ratios always improve inverter utilization and the capacity factor. The measurement of inverter utilization is capacity factor—the ratio between actual and maximum energy production.
Thus a 9 kW PV array paired with a 7.6 kW AC inverter would have an ideal DC/AC ratio with minimal power loss. When the DC/AC ratio of a solar system is too high, the likelihood of the PV array producing more power than the inverter can handle is increases.
What is a good DC/AC ratio for a solar inverter?
Because the PV array rarely produces power to its STC capacity, it is common practice and often economically advantageous to size the inverter to be less than the PV array. This ratio of PV to inverter power is measured as the DC/AC ratio. A healthy design will typically have a DC/AC ratio of 1.25.
The ratio between these capacities, known as the inverter loading ratio (ILR), profoundly influences the calculation of the capacity factor. Thus, a PV capacity factor calculated using a DC-rated capacity has a higher denominator and, thus, a lower ratio than a PV capacity factor calculated using an AC-rated capacity.