Thanks for all the replies, I appreciate it.
Right, it is 120V, not sure why I keep saying 110V.
I have attached a picture here. It is indeed a 20a circuit. A neighbor is currently using the bottom receptacle, and I am hoping to use the top receptacle. Assuming the two receptacles are connected to the same 20a breaker, would charging two EVs likely to trip the breaker (as opposed to 15a breaker).
I bought the condo a few months ago. The HOA has been trying to retrofit the garage for some time, there have been numerous committee meetings and board meetings, but seems like we are at an impasse. Great that your friend managed to do it. Do you think he would mind sharing his design?
95% likely that both receptacles share one circuit.
So the other person using that receptacle: Do they have the 5-15 adapter, or a 5-20 adapter?
If a 5-15 then it will be drawing a max of 12a. If 5-20 then a max of 16a. Per the NEC, you do not ever want to draw more than 80% the capacity of the circuit when using a "continuous load" (which an EVSE is per the NEC definition). Also, over 80% you are likely to blow the breaker as it heats up at some point.
Two EV's on a 20a 120v circuit is not likely a very tenable solution. In theory you could time share by using a transfer switch of some kind (or trying to coordinate schedules somehow, perhaps using an API based tool), but the using "schedules" thing likely would not meet code without a hard transfer switch. You could also each commit to setting your cars to draw only 8 amps each (assuming nothing else was on that circuit), but this would be even more painful since the fixed charging losses would eat nearly all that electricity, leaving very little to actually charge.
So that looks like conduit inside of concrete probably? If you were really lucky, you might have conduit with enough space available in it back to a panel that had sufficient capacity remaining (most likely limiting factor would be a step down transformer) that you could add say a second circuit just for yourself separate from your neighbor. Depending on how things are setup, maybe you could even leave the existing circuit in place (since I am betting it also serves other receptacles elsewhere) and you could add a dedicated circuit for you and for your neighbor (that would then meet code btw as long as they had a GFCI outlet on them). If there was conduit space available and spots in the panel and capacity on the transformer, then this might be really inexpensive to re-conductor and pop in a couple of breakers. For your driving pattern this might work just fine for you.
Heck, you might even be able to get a 240v circuit going. I just realized that if you did a 208/240v circuit you and your neighbor Tesla could install Wall Connectors and link them. So even if all you could support was a 20a 208v circuit, you could have them linked such that it smartly shared that capacity. When both are charging, you would each get 50%, but when only one needed juice it would get the full thing (or maybe not quite, since I think it reserves something and holds it back for the other car? - not 100% sure)
For my friends setup, I don't remember all the details, but his Condo was very modern and had modern electrical switchgear. They have a plenty large feed from the utility and they had a single breaker position available of I think 800 amps on the main switchgear. They ran that to another piece of switchgear which I think had two 400a breakers. Then from each breaker they fed a set of panels that were "stacked" on different floors of the garage. So one panel on the East side and one on the West side of each floor of the garage. All the vertically stacked panels shared a single 400a bus (feed in and fed out of every panel).
So that basic infrastructure was relatively inexpensive. You are talking just core drilling, conduit, panels, and the switchgear breakers (plus all the labor of course). Then as each tenant decides to get an EV they pay to add conduit from the closest panel to their parking spot where they bolt a transformer above each spot (on the wall or something) to just feed that one spot. Each person decides how big a transformer and wire to run depending on their needs. This allows for incremental deployment of EV charging without a one-size-fits-all approach. I think they had some scale solution where each person to deploy EV charging paid some of the common infrastructure costs based on the number of amps of service they wanted.
Since the wire to each parking spot was running at 480v the conduit and wire costs were much lower than say 208v. Then they also purchase a 480 to 240v stepdown transformer for each spot instead of stepping down to 208v. It is 15% faster than 208v for the same wire! I think they did put a meter on the 800a feed that was dedicated to EV charging just so they could keep tabs on how much the EV users were using. If the $10/mo they charged each one does not end up covering it in the future they can just up that rate, or eventually, they could go make every EV user get sub-metered, but that again was just not worth it today.
