Also, while not necessary trivial, it is not hard to throttle consumption of devices, and if it's with two circuits, one for devices that care about voltage, an

Also, while not necessary trivial, it is not hard to throttle consumption of devices, and if it's with two circuits, one for devices that care about voltage, and one for devices that actually brown out. The latter is easy to scale by just reducing the voltage far enough that it doesn't sink too much power, and devices like e.g. desktop or server computers are theoretically easy to rapidly throttle, e.g. by reducing cpu clock to a few hundred megahertz, halting HDD operations or even cutting their power (most are made to handle hot-swap well). A large, modern CPU with 140 W TDP can cut usage within 10 ms to 10W, but dram can't scale that way due to how it works, or rather, this scaling is not supported in mainstream hardware. If you use a small supercapacitor, which commonly has a minimum discharge time of about 2~20 seconds (similar to Lithium-ion pouch cells "LiPo", which are available with different "C" ratings, and negatively correlated gravimetric/volumetric energy density and maximum average discharge power (i.e., optimizing discharge current vs time to maximize the ratio of total power extracted divided by time until empty). You need more metal in the electrodes and the plate/foil that aggregates the current of the individual electrodes, leaving less space/weight for the parts that actually store energy.), you can use much more advanced power reduction techniques for electronic devices, as you have time for something approaching a proper shutdown. Compare e.g. the time your Laptop takes until it is off from the moment you close the lid. Oh, and yes, these capacitors are cheap. One about 1kg / 1 liter size for about 100$ can provide 20kW average power, for 2 seconds. The main difference is that they don't care (much) if you cycle them at 100% depth of charge, apart from internal losses heating it up and thereby causing damage.