Does the value proposition of microinverters and panel optimizers lose its luster at the megawatt scale?

Microinverters and panel optimizers can improve energy harvest, simplify installation, and decrease balance-of-system cost. This is the value proposition and the reason why paying more initially can provide long-term benefits. 

About a year ago, we reported on the largest microinverter and optimizer installations -- and the biggest that Enphase, SolarEdge, or Tigo were able to claim were commercial applications in the hundreds-of-kilowatts range.

At that time time, Jurgen Krehnke was President and General Manager of SMA America, and he told Greentech Media, “The SMA microinverter can easily scale above 2 kilowatts. However, we believe microinverters are not cost-effective above this limit. Microinverters are excellent for difficult roof orientations, starter systems, and small applications, but once you get above 2 kilowatts, microinverters are not cost-competitive with leading string inverters, and the performance gains, as shown by independent testing, don’t warrant the extra expenditure required for large systems."

Enphase (ENPH) just announced a 2-megawatt (AC) microinverter solar project at Ontario, Canada's Vine Fresh Produce. It's Enphase's largest project yet -- the three-phase system was installed under Ontario's Feed-In Tariff (FIT) program by Sentinel Solar of Vaughan, Ontario and used more than 9,000 microinverters with more than 9,000 JinkoSolar modules mounted on greenhouses.

SolarEdge VP Lior Handelsman spoke of his firm's optimizer installations. SolarEdge has scores of installations worldwide in the 200-kilowatt to megawatt-range. Handelsman said that SolarEdge has "several" 2-megawatt installations up and running and will have a 2.5-megawatt installation running within a month; an 8-megawatt project is slated to be energized by March 2014.

So if module-level power electronics (MLPE) are creating value at the wholesale distributed generation size, is utility scale next?

MJ Shiao, GTM Research's Senior Solar Analyst, had this to say: "In general, the business case for MLPE is not as strong in utility systems as it is in residential."

Preserved value in large systems:

  • Eliminates module mismatch losses (not just in year one, but throughout the lifetime of system), which can be as much as 1 percent to 2 percent in year one and more as the system degrades
  • Improves system uptime: if one microinverter fails, only one module fails

Potentially preserved value:

  • Installation cost benefits (e.g., you don't have to pour a cement pad, deliver and mount the central inverters, logistics)
  • Monitoring granularity: Will an owner of a 2-megawatt system really care about a single module when the system has 8,000 of them?
  • O&M ease in terms of targeting the failing or underperforming module accurately

Lost value:

  • A lot more difficult to make the economics to work comparing micros to large central inverters as opposed to micros to string
  • A lot less shading in a ground-mount system vs. the typical rooftop project

Lior Handelsman of SolarEdge notes, "The same benefits of MLPEs that made them so successful in the residential space also exist in the commercial PV space. SolarEdge's solutions provide a very dramatic reduction in BOS cost by making the PV strings 50 percent longer and by eliminating most of the combiner boxes needed for these systems. [...] Though the energy gain is usually smaller than what is experienced in residential, there is still a 5 percent to 15 percent energy gain that can be achieved."

Here are some images of Enphase's record-setting system.