Silver Spring Networks has been poised to hold an initial public offering since June, planning to raise up to $150 million -- but it looks like it’s going back to investors for $30 million in debt and options financing first. That’s according to a Monday federal filing by the smart grid networking startup, which has raised $24 million of the round so far.

With the new financing in hand, Silver Spring has raised just under $300 million to support its impressive surge into the smart grid scene. The Redwood City, Calif.-based company has seen more than 8 million smart meters with its networking and communications technology inside them installed around the world in dozens of deployments, and has a total of 17 million meters under contract.

Big clients including Pacific Gas & Electric, Pepco, Florida Power & Light, Oklahoma Gas & Electric and Sacramento Municipal Utility District have helped Silver Spring take a leading role in North American smart meter networking projects. But with the vast majority of its revenues coming from a few big smart meter deployments, it’s also under pressure to diversify its lines of business.

Indeed, Silver Spring’s latest amendment to its S-1 filing shows the company saw billings decrease from $193.9 million in the first nine months of 2010 to $183.3 million in the nine-month period ending Sept. 30, 2011. That’s a trend the company said would continue into the fourth quarter of 2011, as one key customer nears the end of its deployment, according to its filing. Silver Spring also saw third quarter revenue of $60.2 million, down from $68.8 million in the second quarter, though up from the first quarter’s $46.7 million.

Silver Spring isn’t profitable yet either, with a third-quarter 2011 loss of $21.7 million, a second-quarter 2011 loss of $21.1 million and a first-quarter loss of $33.4 million. So far, it has accumulated losses of about $378.5 million since 2008. Notably, however, the company is showing a gross profit of $11.9 million for the first nine months of 2011, a first for the company, compared to annual gross losses for 2008, 2009 and 2010.

So why has Silver Spring gone back to investors rather than brave the public markets? Given the financial turmoil gripping the greentech industry and the global economy in general, it might not be such a bad idea.

Indeed, we’ve seen a host of well-funded greentech startups with IPO plans taking their sweet time with them this year. Solar thermal power startup BrightSource Energy laid plans to raise up to $250 million in an IPO in June, but hasn’t yet. Microinverter maker Enphase Energy, biochemical science company Genomatica, wood-to-ethanol stalwart Mascoma and other would-be green IPO aspirants are also waiting in the wings.

Silver Spring’s IPO hopes do stand out amidst a sea of corporate acquisitions in the smart grid sector, the latest being Siemens’ purchase of eMeter and the biggest being Toshiba’s $2.3 billion acquisition of smart meter giant Landis+Gyr. On the short list of other smart grid IPOs, distribution grid technology vendor Ambient did file IPO plans to raise up to $57 million in August.

Beyond its big smart meter projects, Silver Spring has a host of distribution grid, plug-in vehicle and demand response pilots. Silver Spring is working with Maui Electric Co. on a smart meter-to-home energy management pilot, as well as a DOE-funded solar power integration pilot with Oklahoma Gas & Electric.

Interestingly, Chief Operating Officer Warren Jenson recently left his post at Silver Spring, VentureWire reported last week.