The good news is, if you limit running the AC during daytime, it is easy to power them with solar energy, as the need for AC implies a lot of sun shine. These days the German grid is powered between 30-40% by solar only. And one would expect this percentage to raise quickly in the next years. Of course, if you are a home owner, you could run your AC directly by your solar, completely removing any network impact (and consequently any additional carbon output).