Volts subscribers are likely well aware of the fact that a fully decarbonized energy system is going to require an enormous amount of hydrogen to fill in the gaps left by wind and solar. What's more, they are probably aware that hydrogen comes in a dazzling variety of colors, from blue to gray to brown, depending on the carbon intensity of the production.In the end, though, only one such color matters: green. That is to say, a fully decarbonized energy system is going to require lots and lots of hydrogen made with renewable energy, with no carbon emissions. The way to do that is to run water and electrical current through an electrolyzer, which splits the hydrogen off from the oxygen.Currently, about 95 percent of the world's hydrogen is made using fossil fuels. Green hydrogen — hydrogen made with renewable energy and electrolyzers — comprises only a sliver of the remaining 5 percent. Yet it’s going to have to scale up to 100 percent in the next several decades, even as demand for hydrogen rises.This is all a familiar story, at least to energy nerds. But if you're anything like me, the more you think about it, the more you realize that, despite the key role they play in that story, you don't actually know very much about electrolyzers themselves. What are they, exactly? What do they look like? How can they be improved? What policy is supporting them?To talk through these questions, I contacted Raffi Garabedian, the CEO of Electric Hydrogen, a startup that has set out to rapidly drive down the cost of green hydrogen. Garabedian, who was previously chief technology officer at First Solar, believes that the market for green hydrogen today is roughly where the solar market was in 2008, with all the attendant risks and opportunities.Garabedian (quite patiently) walked me through the basics of electrolyzers, the current state of the market and the technology, the kind of cost improvements he believes are possible within the next five years, the increasingly supportive policy environment, and the future of green hydrogen. Get full access to Volts at www.volts.wtf/subscribe