Just adding my three cents. A 2018 M3 LR (that's a pre heat pump design) when plugged into an outlet in Maryland, outside temperatures at 20F or so, wouldn't charge. Period. 1.44 kW was being drawn, right. But that wasn't enough to get the battery warm enough to charge.
To the OP: Just so you understand what's going on here with Power, and what your options are:
Standard practice in the US is to have split phase power attached to the main breaker panel. This consists of three wires:
- Neutral. Connected to a ground stake at the building power entrance, and, at the main breaker panel, also connected to safety ground. Connected to the Neutral Bus Bar in the breaker panel.
- Hot #1. 120 VAC when measured between Hot #1 and Neutral. This is connected to the First Hot Bus Bar in the breaker panel.
- Hot #2. When measured between Hot #2 and Neutral, one also sees 120 VAC. Now, the tricky bit: Both Hot #1 and Hot #2 are sine waves. When one is going up, the other is going down and vice versa. A voltmeter connected across Hot #1 and Hot #2 shows 240 VAC. This Hot is connected to the Second Hot Bus Bar in the breaker panel.
If one looks at a breaker panel, one will notice that there's slots for breakers. The first breaker at the top is connected to Hot #1 Bus. The next breaker down is connected to the Hot #2 Bus; the next breaker down is connected to the Hot #1 bus again, and so it continues down the vertical column of slots.
If one wants a 120 VAC circuit, then the a breaker is clipped to Hot #1 or Hot #2, and has a wire coming out of the breaker, normally colored black. A white wire is connected to the Neutral bus bar, and this neutral, and the hot, goes off to power lights and standard 120 VAC wall sockets and such.
If one wants a 240 VAC circuit,
a duplex, ganged breaker that covers two, count 'em, two slots is used. Each of the two breakers (this is for HVAC, electric ovens, and the like) has a single wire coming out: Those two wires have 240 VAC between them, and are routed to the load, which can be hard-wired (for HVAC air conditioning compressors and the like), or a socket (NEMA15-50 or the like) for an electric stove. Usually, but not always, a Neutral and a Safety Ground will go along with these wires.
Here's the chart for NEMA sockets, courtesy of Wikipedia:
So, suppose that your garage has a NEMA5-15, 120 VAC, single 15A breaker. Looking at the chart, it's got a Hot, a Neutral, and the pin has the green safety ground, and is good for 15A peak, 12A steady state (as in a Tesla).
In principle, with management's agreement, one could go to the breaker panel, remove the 15A single phase breaker and disconnect the hot and neutral wires; let's say one is black and one is white.
Over at the other end in the garage, remove the NEMA5-15 outlet and put in a single NEMA6-15 socket, using the white and black wires on the two hots and the safety ground on the ground pin.
Back at the breaker panel, connect the white and black wires to the duplex breaker.
At this point, you now have a 240 VAC, 15A circuit, that can supply 12A steady. That will provide 2.88 kW to the car, double the power you've got at 120 VAC.
The only thing you need at this point is to spend $15 over at Tesla to get the NEMA6-15 adapter.
Now, it's just possible that the outlet in your garage is a NEMA5-20, capable of 20A peak, 16A steady state, and the breaker presently in the panel is a 20A, not a 15A breaker. You can tell this because of that funky slot in the socket in the garage that has that right-angle blade. If that's the case, you can do the above stuff, but use a 20A duplex breaker, rather than a 15A duplex breaker, a NEMA6-20 in the garage, and the Tesla adapter for a NEMA6-20. This would give you 16A at 240 VAC, 3.84 kW, which would be better for your purposes.
None of the above involves pulling wire to the detached garage.
Now, you can get much better charging rates if:
- Your breaker panel has additional capacity that can support, say, an additional 50A or 60A load. An electrician does a load analysis to figure this.
- You or someone is willing to lay wire that's good for 50A or 60A from some breaker panel or other to the garage.
- Ideally, you'd like to have a Tesla Wall Connector, good for 48A on a 60A circuit in the garage (it's cheaper to do it this way than play with high-quality sockets and GFCI protectors) (48A, which is the most any Tesla does these days, gets you 11.52 kW, which is more than enough to warm up your car and charge it in the dead of winter.)
If the breaker panel has the capacity, the cost for doing the above (outside of the Wall Connector) is probably between $500 and $2000, most of that having to do with the cost of the wire and the time to do the labor. Note, however, that the world is going electric anyway, and that NACS is going to be the future connector for electric vehicles. So property management might be willing to help foot the cost, or at least not be adverse to the idea for the benefit of future renters.
People will pick some of the above apart, especially as there are always Details. Best bet, if you're going this route, is to check Tesla.com for a list of electricians that do this kind of work in the area and get several quotes.
Finally: Remember what you're paying the local utility for is
energy, not "voltage" or "current" per se. Let's say you've got a 72 kW-hr battery in the car, it's half-empty at 36 kW-hr, and you want to charge it to 72 kW. So, you need 36 kW-hr. Whether you get that at 1.44 kW (12A at 120VAC) which takes 25 hours, or at 11.52 kW (48A at 240VAC) which takes 3.125 hours, you're paying
for the same amount of energy. Plus or minus bits about having to get the battery warm, first.