I understood the 1.2-1.5 trillion number to be the cost of "fusion as a viable energy source" not the cost of ITER. ITER itself, to be clear, won't generate ele

I understood the 1.2-1.5 trillion number to be the cost of "fusion as a viable energy source" not the cost of ITER. ITER itself, to be clear, won't generate electricity. It's a demonstrator project that proves the viability of some of the technologies that would be prerequisites to an eventual successful electricity generation project. Its planned successor, DEMO, will be even bigger, and will be the first one that actually generates net electricity, but even that won't be geared towards commercial use on the grid -- nobody will ever build these things for commercial use, even if we get to the point more energy comes out than goes in, if they cost tens of billions apiece. Even if both ITER and DEMO go exactly to plan, multiple additional major technological advances will be necessary before the any of it is commercially viable.