No decision has more impact on the system cost and performance than the choice of inverters as this dictates design constraints for much of the balance of system. Today, system designers have more options than ever when architecting solar systems. While this may seem like a great advantage, these options necessitate an ever-growing number of decision points in the design process.
Before selecting brand or model the designer must first choose the macro level class of inverters, central or three phase string inverters. Until recently, the normalized price of string inverters (as measured in $/W) was much higher than central inverters, making the decision to use central inverters for utility-scale quite straightforward. That unit price gap has greatly diminished, resulting in a heightened debate on the relative merits of central and string inverters, often without empirical data to support the arguments.
The jury is still out on which is the so-called “best solution” and likely for good reason as the overall system size has such a significant impact on the relevant answer. In my article for Renewable Energy World, I analyzed the relative merits of central and string inverters in a typical system in North America.
The analysis is limited to the relative costs of central and string inverters for utility-scale projects in North America in three areas: CAPEX, inverter service life and true cost of service.