Yes, 50% seems to be a fair assesment of current PEM fuel cell efficiency. Apparently, the PEM fuel cell itself can get up to 60% efficiency, but there are auxi

Yes, 50% seems to be a fair assesment of current PEM fuel cell efficiency. Apparently, the PEM fuel cell itself can get up to 60% efficiency, but there are auxiliary services (cooling, supply and exhaust pumps, etc) that most people don't think about that drive the system down to about 47% reliable output efficiency. That's not bad considering zero GHG emissions, and other benefits such as scalability and power density of the cells, but I'm still hopeful for significant improvements in the next decade (I suspect this may be significant offset in the form of greater H2 storage mass/volume energy density).