If we'd really want to lower the energy usage of our applications we probably have to simplify along the whole chain. Using Astro means the whole process relies probably on NPM, the build cycle is probably also more energy intensive. Static HTML hosted on some dirt cheap server is probably more environmentally friendly than hooking up to some API and giving us various experiences based upon the mix of the grid.

To me the savings as mentioned in the article feel rather superficial compared to the energy consumed just getting the basic infra for this up & running. Somehow this feels like greenwashing.

All addressed in TFA. The author writes multiple times that this is experimental, would be a drop in the bucket, and brings its own power cost to implement - and that GAW is in no way intended to directly "fix" web power consumption.