PETALUMA -- Enphase Energy Inc. (NASDAQ: ENPH) on Tuesday reported second-quarter sales increased 15 percent and quarterly net loss nearly was cut in half.

The Petaluma maker of microinverter systems for solar panels reported $58.2 million in second-quarter revenue, up 15 percent from $55.7 million a year before. Half-year sales increased 5.5 percent to $103.7 million from $98.3 million a year prior.

“We had a great second quarter,” said Paul Nahi, chief executive officer. “Once again, we improved our gross margins...while continuing to maintain tight control over operating expenses, which we kept flat for the third consecutive quarter. We also made great strides in improving cash flow from operations."

For the first time, he said, more than 20 percent of revenues came from sales abroad. That's up from roughly 15 percent in the first quarter and 10 percent in the fourth quarter of 2012.

Net loss improved to $6.27 million in the second quarter from $11.2 million a year before. For the first half of the year, net loss improved to $16.5 million from $21.4 million.

 Non-GAAP gross margin was a record 28.1 percent in the second quarter, an increase of 360 basis points from 24.5 percent a year prior.  

Also on a non-GAAP basis, the net loss was $4.8 million, or a loss of $0.12 per share, compared to net loss in the second quarter of 2012 of  $7.3 million, or a loss of $0.19 per share

Enphase reported selling 399,000 inverter systems in the second quarter of 2013. IHS Research named the company No. 1 residential inverter supplier in the Americas by revenue share, and Enphase's web-enabled monitoring software was named No. 1 power electronics monitoring provider by GTM Research worldwide by number of new sites for 2012.

Mr. Nahi said the company's deal with Lenner homes, inked a couple of months ago, is working out well. Enphase entered into a strategic relationship with nation-wide home builder Lennar through its newly created subsidiary, SunStreet Energy Group, to provide microinverters to the new home construction market.

Enpahse employs 400 in its Petaluma headquarters.

The price of Enphase stock fell 54 cents, or 8.2 percent, to $6.06 a share at the close of trading Tuesday. The price continued to slip to $5.39 at 4:30 p.m. in after-hours trading.