Yeah, to the OP:
Standard wiring for homes in the US and Canada have something called "Split Phase". Up on the power pole, a transformer has three output wires:
- One wire is Neutral. When it gets to the house, it gets bonded to the ground bar inside your breaker panel and, incidentally, gets connected to a 6 foot copper ground stake that is, natch, pounded into the physical ground.
- One wire is a Hot. A voltmeter connected between the Hot and Neutral shows up as 120VAC, plus or minus a bit. This particular wire gets bolted onto the back side of the meter on your house; another wire takes this voltage and connects it to one of the two bus "hot" bus bars in your breaker box.
- The final wire is also a Hot. A voltmeter connected to this hot and Neutral also shows up as 120 VAC. The tricky bit: Each hot is a sine wave. While one sine wave is going up, the other sine wave is going down. A voltmeter connected between the two hots shows up as 240 VAC.
Note that the meter on the house has four big lugs on the back: One for each hot coming in, and one for each hot coming out.
So, in the above situation, if one looks at the breaker box in your house, for a (typical) vertical row of slots, the first slot at the top is on one hot; the next one is on the
other hot, then back to the first hot, and so on, all the way down the column of slots. When one wants 240 VAC for, say, the HVAC in the house or an electric drier, a duplex, ganged breaker will be plugged into two adjacent slots, and the voltage between the wires coming off this pair of ganged breakers will be 240 VAC.
Any hot to ground/neutral is 120 VAC, and that's for lighting, standard power sockets, and appliances that work off of 120 VAC.
Now, in commercial properties, people get three-phase AC. There's three hots and a neutral. Each hot to neutral is 120 VAC. The meter will have a total of
six lugs on the back, one for each of the three phases coming in, and one for each of the three phases coming out.
Let's call the three phases A, B, and C. Let's arbitrarily say that Phase A is at zero degrees; Phase B is at 120 degrees; and Phase C is at 240 degrees. Do the math with sine waves and all, and one will discover that the voltage between
any two phases is 208 VAC. And, if one looks at the breaker box, instead of having this alternating, "first this phase, then that phase, then the first phase again", one will get, in a vertical column, Phase A, Phase B, Phase C, Phase A again, Phase B again, and so on. A duplex breaker on two adjacent slots will give you 208 VAC.
So, go to a public charging station in a Supermarket parking lot? More likely than not, that Supermarket has 3-phase AC, and the Chargepoint (or whatever) charging stations will supply current at 208 VAC, because that's what's available: Two phases of the three-phase system feeding the Supermarket.
Now, that split-phase power that one sees on one's house typically comes from some transformer with 440 VAC in (or something) and that split-phase stuff coming out, and the split phase goes not to just one house, but usually several. But it's not written in stone that this might happen. It's Just Possible that, for some weird historical reason, that a bunch of houses on some street somewhere all got supplied with two phases of a 3-phase system, and they've all got 208 VAC between the two phases actually supplied to the house.
If that last thing is what happened to you.. Well, weird, somewhat non-standard, but not harmful in any way. HVAC systems and Tesla Wall Connectors can handle 208 VAC just fine. You'll get less power delivered to the car that way (say, 208 @ 48A = 9.9 kW, 240 @ 48A = 11.5 kW), but not enough to keep one up at night.
But, there's another possibility. Say you had some piece of machinery that was, for some vaguely insane reason, truly specific that it
had to have 208 VAC. And you told your electrician that. And your electrician, in this scenario, noted that you had 240 VAC split phase. Well, one can't just connect wires, wave a magic wand, and arbitrarily make 208 VAC happen.
Except that, in a way, one
can do that. There is such a thing as a step-down transformer. Heavy, made of iron, with lots of wires running around in small circles, and 240 VAC in, 208 VAC out. Power out is about the same as the power in, minus some losses that make the transformer slightly warm.
However.. these things, assuming you've got such a thing, very positively have power limits. Some of that is how much heating one can have on the wires in this thing (assuming you've got this thing) which, if the heating is enough, leads to breakdown of the insulation inside the transformer, which is arcs, sparks, and breakers popping open time. And there's some heating of all the heavy iron in there. And that transformers have power limits where the iron gets magnetically saturated, which is Bad News.
So, if your electrician knew what the power requirements for your machinery was, and decided that a transformer was the way out, he'd've picked a transformer with the right power rating for your machinery, picked the right breaker on the panel to supply that power, and the right wire to handle that current. You don't want to violate
any of that when charging your Tesla.
Another possibility.. It's Really Common for equipment that's rated for 200-odd VAC to be able to handle both 208 VAC and 240 VAC. If your electrician looked at the specs on your gear and it
said that it could take 240 VAC, he may have ditched the whole transformer business right off, saved you some money, and saved himself some time. And your understanding about what you've actually got there may be faulty.
You could figure all this out in about ten minutes with a voltmeter. Or a friend with a voltmeter.
208 VAC in residential is, like, odd.