Every Plug Power Investor Should Keep an Eye on This Number

From a business standpoint, Plug Power (PLUG -0.41%) has clearly succeeded this year at selling customers on the value of its fuel cells and hydrogen business. Investors, on the other hand, haven't exactly been sold on the value of Plug Power stock. While the S&P 500 has ripped more than 24% higher since the start of the year, shares of Plug Power have plummeted about 43%.But management remains ever hopeful that the company is on the right path, and financial success is right around the corner. There are a ...