they are the clear leader in the microinverter space. They already have demonstrated a successful product, and they are growing share rapidly. It’s a technology-intensive business, but it’s not a capital- or manufacturing-intensive business.”
And the easier it gets to install and maintain solar panels, the faster solar energy will spread as a way to power homes, Kortlang and others argue. “Inverter companies are focusing innovation on residential solar because they recognize the high growth potential in this area,” says Lynn Jurich, co-founder and president of San Francisco-based SunRun, which installs solar arrays on homes and then charges homeowners for the power. “In fact, 2011 may be the year in which total installed megawatts of residential photovoltaics surpasses the total of the utility and non-residential sectors combined.” In its own installations SunRun uses both Enphase’s microinverters and equipment from other companies like Tigo, depending on each customer’s needs, Jurich says.
It’s a sign of Enphase’s high-tech orientation that the company was started by two telecommunications experts: Martin Fornage, formerly a fiber optic engineer for Advanced Fiber Communications, and Raghu Belur, a former designer of high-speed optical communications equipment for Petaluma-based Cerent, which was acquired by Cisco in 1999 for $7 billion. Nahi says Fornage became interested in inverter technology after installing solar panels on one of his own homes. “He saw the challenges associated with traditional inverters, and being an engineer, he figured he could solve that problem by developing a microinverter,” Nahi says.
Fornage and Belur started Enphase in March 2006 and invited Nahi, formerly the head of telecom semiconductor designer Crimson Microsystems, to join as CEO at the end of that year. There wasn’t much market data on inverters at the time, Nahi says. Because inverters account for only about 10 percent of the cost of a solar installation, they were seen as part of the plumbing. The whole focus in the solar industry was on the panels themselves and how to make them cheaper and more efficient. “Certainly nobody had applied a Silicon Valley mentality to inverters before,” Nahi says. “So I convinced myself that this was a very exciting opportunity.”
But to build a microinverter, “You can’t just take a regular inverter and shrink it,” Nahi says. To convert as little as 200 watts of DC to AC efficiently, Enphase developed a custom mixed-signal chip that manages the other electronics inside each microinverter. It constantly analyzes the current and voltage of the electricity coming in from the panels and turns the other elements inside the Enphase box on and off to ensure that there’s as much AC power coming out as possible, and that it matches the 60-hertz frequency of grid power. (That’s a necessity, since residential solar arrays essentially mesh with the larger utility grid and sometimes feed power back into it.)
Enphase spent more than a year testing the first version of its product. The company had to be sure its microinverters—which live on rooftops, bolted to the same rails that hold solar panels in place—would be safe and reliable even under conditions like extreme heat and cold, rain, lightning, and most importantly, power grid fluctuations.
“The grid is a very harsh, unpredictable environment; it’s far more variable than we thought,” says Nahi. “There are changes in voltage, frequency, and amperage due to a million reasons, from high winds slapping power lines to poor wiring. It’s not like networking and communications. It’s very non-deterministic.” The company placed thousands of test units around the country and recorded the waveforms coming in from the grid. It then devised quality-assurance procedures to make sure no unit leaves the factory until it’s been tested against all of these waveforms, in amplified form. “That’s why the beta testing took a year,” says Nahi.
Enphase shipped its first microinverter in 2008, and the product “very, very quickly became incredibly popular with installers,” says Nahi. There are a couple of reasons for that, and they’re worth sizing up separately, since they point to lessons the larger cleantech industry is probably going to have to learn to achieve widespread uptake of unfamiliar new technologies.
The first reason is that microinverters make life easier for solar installers, whose recommendations strongly influence which type of inverter system a homeowner chooses. With central inverters, designing a solar array can turn into a huge
