Footnotes / references
Financials from Enphase Energy

Enphase Energy is a NASDAQ-listed energy technology company headquartered in Petaluma, California. Enphase designs and manufactures software-driven home energy solutions that span solar generation, home energy storage and web-based monitoring and control. Enphase has shipped about ten million solar microinverters, primarily into the residential and commercial markets in North America, Europe and Australia. Microinverters convert the direct current power from the solar panel (DC) directly into grid-compatible alternating current (AC) for use or export. Enphase was the first company to successfully commercialise the microinverter on a wide scale, and remains the market leader.

A number of companies and institutes had promoted the solar micro-inverter concept through the 1990s. The basic idea is to reduce the power handling of a conventional inverter design so that it matches the output of a single panel. This so reduces the size of the inverter that it can be placed on the back of the panel, producing an "AC panel". Such a system can be connected directly to the grid, or to each other to produce larger arrays. This contrasts with the traditional solar inverter approach where many panels are connected together in series on the DC-side and then run en-masse to a single larger inverter. Several products based on the micro-inverter concept were introduced in the 1990s and especially the early 2000s, but none were widely successful due to a number of factors.

In the aftermath of the 2001 Telecoms crash, Martin Fornage of Cerent Corporation was looking for new projects. When he saw the low performance of the string inverter for the solar array on his ranch, he formed Enphase Energy with another Cerent engineer, Raghu Belur, in 2006. Backed by $100 million in private equity, in 2008 they released their first product, the M175, to moderate success. Their 2nd generation product, 2009's M190, was far more successful, with sales of about 400,000 units in 2009 and early 2010. Enphase quickly grew to 13% marketshare for residential systems by mid-2010, aiming for 20% by year-end.

They shipped their 500,000th inverter in early 2011, and their 1,000,000th in September of the same year. The 3rd generation M215 was released in the summer of 2011, and had sold over a million of all models in 2011, bringing their installed base to 1.55 million inverters and 34.4% market share. A 4th generation, the M250, was released in 2013.

As of 2012, their inverters captured 53.5% market share for residential installations in the US, which represents 72% of the entire world micro-inverter market. This makes them the sixth largest inverter manufacturer, of any kind, worldwide. Enphase has experimented with the European market starting in France and offering sales in France, Belgium, the Netherlands, Luxembourg and Italy. However, they had considerably more success in the UK, and later, Australia. As of 2013, approximately 20% of their sales is outside North America.

Enphase continues to see increasing pricing pressure due to rapidly falling prices in the inverter market. In spite of several effects that should cause stability, prices for inverters are predicted to fall 11% during 2013. Market leaders, especially, face continued market share erosion in the face of newer companies, most of them from the far east.

All Enphase microinverters are basically the same internally, with differences in the maximum amount of power they can handle and the cabling system being the major differences between models.

The M175 was their first product, released in 2008. It was designed to output 175 Watts of AC power, but is capable of up to 5% over that. The M175 was packaged in a relatively large cast aluminum box, similar to the boxes used on cable tv amplifiers seen on telephone poles. Wiring was passed through the case using compression fittings and the inverters connected to each other using a twist-lock connection. A limited number of M210 models, based on the same generation system, were also available for a limited time.

Due to a high level of failures the M175 was recalled and replaced by the M190 in 2009. The M190 offers a slightly higher power rating of 190 Watts (peaking to 199). The system was packaged in a much smaller case, this time filled with epoxy potting material to handle heat dissipation, and built-in cable connections replacing the earlier compression fittings. The system was otherwise similar, using the same connectors and cabling as the M175, and the two designs could be mixed in a string. Like its predecessor the M175 the M190 has also been plagued by a high failure rate.

Around the same time the company also released the D380, which was essentially two M190's in a single larger case. For small inverters like the M190, the case and its assembly represents a significant portion of the total cost of production, so by placing two in a single box that cost is spread out. The D380 also introduced a new inter-inverter cabling system based on a "drop cable" system. This placed a single connector on a short cable on the inverter, and used a separate cable with either one or three connectors on it. Arrays were constructed by linking together up to three D380s with a single drop cable, and then connecting them to other drop cables using larger twist-fit connectors.

In 2011 the entire lineup was replaced with the 3rd generation M215, combining the features of the M190 and D380. Like the M190, the M215 was a single inverter, now in a much smaller box. Like the D380, the M215 used a trunk cabling system with short connector cables on the inverters. However, instead of one or three-drop cable, the M215's Engage system, used a long roll of cables with connectors spliced into it. The installer cuts the Engage cable to the required length, and then caps the open ends that result.

In 2013 the M250 was released, offering a new grounding system that eliminates the otherwise NEC - required external grounding conductor, increased reliability, and increased efficiency (96.5%), along with a rating bump to 250W. Whereas previous models were all named after the maximum power rating, the M250 actually refers to its peak power. Using the same convention the M190 would be called the M199. The M250 is otherwise identical to the earlier M215 and compatible with the same Engage cabling system.

All Enphase models use power line communications to pass monitoring data between the inverters and the Envoy communications gateway. The Envoy stores daily performance data for up to a year, and, when available, allows Enphase's Enlighten web service to download data approximately every 15 minutes. Customers and installers can review the data on the Enlighten web site.

In 2015 the company launched its fifth generation of products. The S230 and S280 microinverters have the highest efficiency for module-level power electronics at 97%, offer advanced grid functionality like reactive power control, and comply with regulatory requirements like Electric Rule 21 in California and Rule 14H in Hawaii. The next-gen Envoy-S offers revenue-grade metering of solar production, consumption monitoring, and integrated Wi-Fi. The company also moved into home energy storage with its Storage System featuring an AC Battery, a modular, 1.2kWh lithium-iron phosphate offering aimed at residential users that is part of a Home Energy Solution. The Home Energy Solution will launch in Australia in mid-2016.