The biggest problem facing the global energy transition over the next decade isn’t technology or politics. It’s money.

Reconfiguring the world’s power systems to eliminate carbon emissions is going to be a multi-trillion dollar investment project. Over the past few years, clean energy has overtaken fossil fuels in terms of global spending, but one place is still falling short: developing economies. Rich nations tempted to rest on their laurels, now that a promise to mobilize $100 billion a year for climate in such countries appears to have finally been met, should watch out. The real fight is just beginning.