Plug Power Inc (NASDAQ:PLUG) shares fell on Tuesday as the company posted underwhelming quarterly results.

For its second quarter, the hydrogen fuel cell systems manufacturer reported an adjusted earnings loss of 10 cents per share, which was wider than analysts’ expectations of a six-cent loss. The GAAP loss came at 19 cents per share, while the year-ago loss was seven cents per share.

Revenue came in at $22.6 million, topping the year-ago figure of $20.5 million in sales. However, Wall Street were calling for revenue of $28.57 million.

Some second-quarter highlights for Plug Power include the deployment of four more GenKey sites, two of which were power purchase agreement sites. The company also deployes 891 GenDrive units, in line with its projections.

The figure was below the year-ago figures of 955 GenDrive units and six GenKey sites. Fuel cell systems and infrastructure gross margins were 25, while the GenDrive gross margin was 31% and service gross margins were near breakeven.

For its third quarter, Plug Power expects its GAAP gross revenue to be about $130 million, while adjusted gross margins are slated to be between 8% and 12%. The company also predicts to use between $25 million and $35 million in free cash flow.

Over these three months, Plug Power also projects the deployment of 10 GenKey sites and nearly 3,000 GenDrive units. The company said that the period will be the largest in its history.

Management sees a more than 20% increase in the number of GenFuel sites installed, plus an 18% growth in the number of GenDrive units deployed.

PLUG shares fell 5.3% Tuesday.