Bloom Energy, the Silicon Valley fuel cell maker with an estimated $800 million in VC and backers like John Doerr, T.J. Rogers and Colin Powell, is on a short list of green technology startups voted most likely to IPO someday soon, though the company has remained consistently mum on the topic. But what's the value of the San Jose, Calif.-based startup to its investors? The answer depends on who's selling.

Take last week's report from VentureWire on Felix Investments, a firm that has been charged by the Securities & Exchange Commission for allegedly misleading investors. Those charges center around hot tech IPOs like Facebook and Zynga, but in a recent email pitch to customers, company representative Frank Mazzola was offering Bloom Energy shares at a price of $20.50, as compared to the $25.76-per-share price reported from its most recent $150 million round in June

Consider the source of the information, of course. KR Sridhar, principal co-founder and chief executive of Bloom Energy, told VentureWire that Bloom has no relationship with Felix Investments. Even so, it's an interesting target price for the company's shares, falling as it does in between two other reported valuations in the past few months.

The first comes from Advanced Equities, believed to be one of the largest investors in Bloom, which led the company's most recent round. The Chicago-based investment firm, which ousted CEO Dwight Badger in June amidst an SEC investigation, set a value for its Bloom offering at the aforementioned $25.76 per share, for a pre-money valuation of $2.7 billion for the company. That's up significantly from a $1.8 billion valuation pegged to a June 2011 investment, and is the figure most often quoted as of late as a stand-in for the company's potential value on the public market.

The second comes from mutual fund GSV Capital, which invested in Bloom back in 2011. According to GSV's August earnings report, it bought 201,589 common shares of Bloom Energy in the second quarter of 2012, at an average price of $19.12 per share. Granted, it's one of the few Bloom investors that reports such details -- others include Apex Venture Partners, DAG Ventures, Kleiner Perkins Caufield & Byers, Mobius Venture Capital, Madrone Capital, New Enterprise Associates, SunBridge Partners, and Goldman Sachs, to give a sense of the support behind the startup.

If anything, the divergence in reported valuations of Bloom shares matches the uncertainty over whether it can break out with its version of a technology that has so far failed to capture anything close to what its backers have promised over the decades. There is still not a single, pure-play, public fuel cell company that has experienced profitability. Bloom is no different, though CFO Bill Kurtz offered unclear promises of being "halfway" to break-even point in an interview with GigaOm last month. Bloom also sells its fuel cells as a service to take some of the pain out of the initial investment, which could open new markets, though it also requires financing partners.

As for green credentials, Bloom's natural gas-fueled boxes emit far less pollutants than diesel gen-sets, but still produce carbon dioxide, making them less green than solar or wind power. Feeding them biogas, or methane captured from rotting organic material at landfills, breweries, dairies and the like, makes them carbon-neutral, and also offers them heightened incentives under California's Self Generation Incentive Program (SGIP), although a recent state ruling has taken away those benefits for new projects, with an unclear impact on the company's business in its home state.

Bloom's Fortune 500 clients include Google, Adobe, Coca-Cola, FedEx, Wal-Mart and Apple, which revealed it was buying 4.8 megawatts of fuel cells from Bloom to back up its Maiden, N.C. data center. In June, it landed a 6-megawatt project with eBay, which wants 30 Bloom “energy servers” to back up its data center, the biggest project yet for its dedicated IT power backup business. 

In the meantime, Bloom’s biggest single project, a 30-megawatt installation with Delaware utility Delmarva Light & Power, remains under attack in the courts. Nonprofit legal advocacy group Cause of Action filed a lawsuit accusing Delaware Governor Jack Markell and the Delaware Public Service Commission of unconstitutionally setting up a deal in which Bloom agreed to build its fuel cells in the state, and got exclusive financial and regulatory benefits in return. The lawsuit (PDF) also included competing fuel cell maker FuelCell Energy as a plaintiff.