Solar panel micro-inverter manufacturer Enphase Energy is looking to raise $51.5 million in a funding round and has raised around $14 million of that so far, according to a recent filing with the Securities and Exchange Commission.

Solar panel micro-inverters transform a direct current generated by the photovoltaic cell on the panel into an alternating current. The alternating current is fed into a power grid, which can’t accept a direct current. Micro-inverters are built into a single solar panel rather than an array of solar panels. As a result, the total electrical output of a solar array does not suffer when a single solar panel is damaged or in the shade.

Enphase Energy’s micro-inverters are compatible with about 80 percent of solar modules currently on the market.

Enphase Energy filed to go public and raise up to $100 million earlier this month. Like a number of other companies filing to go public this year, Enphase has not been profitable for several years. The company lost $21.8 million in 2010 and $16.7 million in 2009. It also lost $9.3 million in the first quarter this year, up from a loss of $3.7 million in the first quarter of 2010.

The company brought in $18.1 million in revenue in the first quarter this year, up 56 percent from $11.6 million in the first quarter of 2010. It brought in $61.7 million in revenue in 2010, up 205 percent from $20.2 million in revenue in 2009.

Enphase raised $63 million in its last funding round in July last year led by Kleiner Perkins Caufield & Byers. The company raised $22.6 million in a funding round in May 2009 and $6.5 million in January 2008. The company has raised a total of around $113 million to date.

Competitor SolarBridge also recently closed a $19 million funding round led by Rho Ventures and Battery Ventures. SolarBridge’s micro-inverters last around 25 years, compared to typical centralized power inverters that usually last around a decade. SolarBridge also includes a 25-year warranty on its micro-inverters. SolarBridge has raised round $46 million total after launching in 2004.

Petaluma, Calif.-based Enphase Energy was founded in 2006. Its investors include Third Point Ventures, RockPort Capital Partners, Madrone Capital Partners, PCG Asset Management and Applied Ventures, and Bay Partners.

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