Energy storage (battery, flywheel, etc) would solve the transient energy problem, you are correct. Something like the Tesla PowerWall could potentially be scale

Energy storage (battery, flywheel, etc) would solve the transient energy problem, you are correct. Something like the Tesla PowerWall could potentially be scaled up to commercial energy production, but honestly we probably still have 30 years to go there. As for cheaper, it's still slightly more (30%) for PV solar than for nuclear (as far as I can tell). That will continue to come down, which is great. The cheapest clean energy is actually geothermal, but there are only so many places where the plate tectonics work with our current drilling technology. Ironically, drilling advancements for fracking and deep wells will open up the field for geothermal in many more places. As for safety, the 5x number was for plant solar, not rooftop. Production of silicon PV panels is not clean, nor is it safe shipping millions of them around the world. However, the safety is so much higher than coal that I shouldn't really be complaining.