T&D must be sized for the peak of usage, meaning that most of the capacity sits idle, except for the extreme situations. If that peak is reduced, T&D upgrades and expansions are delayed as our energy demand grows, and all the equipment is used more efficiently. (And just as transmission has been neglected in the US for a long time, so has distribution, and we are going to need a ton of upgrades as energy demand grows while we electrify our energy usage.)

In nearly every market, energy use peaks at mid-day, just as solar is peaking. So distributed solar is a peak-shaving system, whereas centralized utility solar still requires the same big peak.

Distributed storage reduces both troughs and peaks, and makes T&D even more efficient.