Upgrade outlet to 220v?

I did the opposite (converting a 220 to a 120) with no problem.

You may not need to replace the wiring. Instead of one 110v hot and one neutral, both can become hot.

At the panel end, you'd connect the former neutral to hot, and voila. There's more to it than that, of course, and you'd have to have an electrician do it. It's just very unlikely you'd have to pull new wires or replace the panel.

stuvwxy99, someone I know did this, in a pre-war building, top floor. I'm not 100% sure if it's related, but he got a fire inside of the socket a few days later, and the A/C burned out. It was all quite a shock.

This is conceivably doable, but get an electrician in. The breakers might be a problem but there are split breakers that might enable some reorganization of the panel to accommodate the double breaker for 220. It is possible to wire a dedicated 110v circuit to 220v, provided, among other things, that the wire is of a sufficient gauge and it is a three wire grounded back to the panel. The size of the circuit will be dictated by the wire size and will be "relatively" low, but more than enough, if it is doable, to power an ac.

Thanks. I took another look at the panel, and there are actually two free slots, so that should not be an issue there. So, it seems that if the current outlet has a hot, neutral and ground, then this could be converted to 2x hot plus one ground, fairly easily? I will of course have an electrician do this.