Even the Governator was at the event, the unveiling of fuel cells made by Bloom Energy, funded by a well-known venture capital group.

As the San Jose Mercury News report about the event discusses, fuel cells are promising, but

…they’re not cheap: The commercial-scale boxes, which look like a big refrigerator, cost $700,000 to $800,000.

EBay started using five Bloom Energy Servers in July. They produce electricity to power space for 2,000 to 3,000 employees and shaved $100,000 off eBay’s power bill …

Assuming the $100,000 was on an annual basis, it took about $4 million worth of equipment to save $100,000, for a payback period, without interest, of 40 years. Not too promising, it seems.

Experts interviewed in the article stated that fuel cells should be able to last at least 10 years, and that it remains to be seen if these devices would last that long (they are difficult to keep from breaking due to brittleness, apparently). But here we see that this is a low time period compared to payback.