For decades to come, we won't have 100% clean energy systems everywhere. Even if you power your AC 100% by solar energy, that solar energy won't be used to displace dirty energy elsewhere. Even if you make absolutely sure you have additional solar energy (I don't know how you'd do that), you still have production emissions for the solar panels.
For the forseeable future, if you can do X with less energy than before, that's an improvement.
During calm hot sunny days in the summer (so.. the ones when you need AC the most), we already have surplus of solar energy and serious problems (in some places) what to do with that energy (you have to dump it somewhere).
No reason. It's obviously better to use power than waste it, but it's not a "serious problem" if we don't. It doesn't damage panels. It doesn't stress the grid. It doesn't cause additional emissions.
For decades to come, we won't have 100% clean energy systems everywhere. Even if you power your AC 100% by solar energy, that solar energy won't be used to displace dirty energy elsewhere. Even if you make absolutely sure you have additional solar energy (I don't know how you'd do that), you still have production emissions for the solar panels.
For the forseeable future, if you can do X with less energy than before, that's an improvement.