Energy will not be free for quite a while, if ever. And while energy for a single flight of a single drone is minimal, having tens of thousand of delivery dron

Energy will not be free for quite a while, if ever. And while energy for a single flight of a single drone is minimal, having tens of thousand of delivery drones, operating 24/7 (or 16 hrs a day) is another matter. Even if cost of production of energy is 0 (and it's not. even for renewable, solar panels need cleaning and occasional replacement, wind turbines need regular maintenance, etc.), there is a large cost of maintaining electric grid. In some places on earth, local solar installations, might be enough, but for most of the planet, we will still need normal grid, and probably even expand them, if we plan to migrate everything to green electricity. I don't know how much electricity you pay where you live, but for me, only around 50% of the bill is actual usage. And since other forms of energy(like gasoline and natural gas) provide significant tax income, this will eventually mean governments will raise electric taxes to compensate, when and if electricity replaces them. So I would not be surprised if cost of electricity stayed the same.