> With wireless charging being 60-75% efficient, the literal worst case scenario is that you go from 2kWh to 3kWh.
Maybe the difference isn’t so low as you estimate it? Maybe the wired chargers use much less power when the phone is not being charged, compared to the wireless chargers? Then the difference could be approximately 0 (as your phone is charged only a few hours per day) to approximately N kWh (due to a constant power draw — nobody will buy a wireless charger to keep it unplugged).
Otherwise, I agree that not upgrading the phone saves even more.
In principle, wireless chargers can have very low power use when idle; I've seen figures quoted as 0.1mW i.e. over the course of a year 0.876Wh (so ~0.0009 kWh). Of course, this will likely vary based on the specific charger in use. I don't think this is substantially different to the idle draw of a wired charger.
The practice is often very different from the principle. I’ve had a set top box that in the “off” state used 29 watts, 24 hours per day. In the “on” state it used 30 watts. In principle, it didn’t have to be so but it was.
Maybe the difference isn’t so low as you estimate it? Maybe the wired chargers use much less power when the phone is not being charged, compared to the wireless chargers? Then the difference could be approximately 0 (as your phone is charged only a few hours per day) to approximately N kWh (due to a constant power draw — nobody will buy a wireless charger to keep it unplugged).
Otherwise, I agree that not upgrading the phone saves even more.