String Inverters Single-Phase Solutions for the North American Market (2011)

While utility-scale PV plants utilizing high-power central inverters make up the fastest growing solar market sector globally, many SolarPro readers may be surprised by the fact that low-power string inverters accounted for the majority of inverter capacity sold worldwide in 2010. Ash Sharma, a member of IMS Research, a UK-based market research firm, presented some compelling numbers at PHOTON’s PV Inverter Conference in Berlin, Germany, in April 2011—compelling numbers for string inverters, that is. Globally, 21 GW of inverters were sold in 2010. Low-power string inverters represented 57% of this total sales capacity. High-power central inverters accounted for 42% of the sales, with microinverters rounding out the field at 1%. While most leading inverter manufacturers design and produce both string and central inverters, based on the current market share percentages, it is a safe bet to assume that manufacturers are devoting significant resources to the advancement of their string inverter products.

While data that represents string inverter market share in the US in its entirety is not publicly available, the regularly updated California Solar Initiative (CSI) database provides insight into inverter manufacturers’ share of the California market and serves as a general reference point for the US market for these products as a whole. SunCentric, a solar consulting firm based in California and Oregon, generated the data included in Figures 1 and 2 for publication in SolarPro. (SunCentric’s recently released 2011 CSI program analysis can be downloaded from the company’s website at The data included in the two charts was sourced directly from the raw CSI data in mid-May 2011, and was filtered to present a clear snapshot of inverter market share among string inverter manufacturers. Residential and nonresidential projects using single-phase string inverters comprised the dataset. Only systems utilizing grid-direct, single-phase string inverters were included. Private-label inverters from companies including SunPower and Yes! Solar were allocated to the original equipment manufacturer. It is interesting to note that the shift in market share between SMA and Fronius appears to be driven in part by SunPower purchasing and branding. SunCentric reported that SunPower has approximately 10.8 MW of Fronius string inverters in process compared to 8.4 MW of branded SMA products.


As the application space for string inverters grows, manufacturers of these products have been positioning themselves to capture North American market share through expanded product lines and manufacturing capacities, strategic acquisitions and an increased presence in North America in both sales and support services. As a point of reference, SolarPro’s 2010 string inverter specification table lists 48 inverter models from eight manufacturers. The updated accompanying table (Click HERE for .xls version) includes 72 string inverter models from 12 manufacturers. Several existing string inverter manufacturers have added models to their product lines and four additional major manufacturers have released equipment for the US market.

To create a clear differentiation between product classes, only single-phase string inverters are listed in this year’s string inverter specifications table. With the exceptions of a few models that are pending CSI eligibility, all of the inverter products included in the table are listed to UL 1741 and are currently eligible for the CSI program. The decision to make CSI eligibility the criteria for inclusion is based on our perspective that if inverter manufacturers are serious about delivering and supporting products in the US, they are surely eager to meet the incentive eligibility requirements for California, the country’s largest solar market.


While seasoned integrators working in North America are familiar with the system design, installation and performance subtleties of major string inverter brands, the companies behind the products and the evolution of the product lines are less well known. The following profiles present detailed information about the companies behind the products, in an effort to shed some light on exactly who is manufacturing the products you are installing. Information included in the company profiles was sourced from interviews conducted by SolarPro staff with company representatives and from information published directly by these manufacturers in investor profiles, earnings reports, company histories and corporate press releases. It should be noted that the depth and thoroughness of the information provided by the various manufacturers during our interview process varied considerably, as did the availability of company-specific information that was sourced during the online research phase of each profile’s development.


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