Hi folks, I configured in the batch of invites that went out on Feb 22 and I'm finally getting around to figuring out the charging solution at home. Got the first quote from a Tesla recommended electrician here in the Bay Area and looks like our electrical load is 69.5 Amps out of the available 100. That leaves us with about 30 Amps. Breaker would be installed in the panel in the garage. Wiring should be pretty straight forward and doesn't have to travel very far to the install spot. Quote below:
1. Install a NEMA 14-30 receptacle on a 30 Amp circuit. Provides 24 amps for charging. Electrician says the car would charge at ~ 22 miles an hour.
Estimated cost - $ 1240
2. Install Tesla wall connector on a 30 Amp circuit. Same charging rate as above.
Estimated cost - $ 1940
Permits and fees - Additional $550
Firstly, the cost seems excessive for what would seem to be a simple install if we go with Option 1. I'm chalking this up to 'Tesla recommended' premium and will get more quotes.
I commute 70 miles a day and although the 30 Amps would be enough to wake up to a full battery based on the charge rate above, I would like to take advantage of the car's higher charging capacity. But what surprises me is that he didn't recommend we upgrade our panel to 200 Amps at all. Does it make any sense to max out current panel in terms of load close to a 100%? Should we even consider not upgrading the panel? (Would make the husband happy
) Would appreciate any input. TIA!
So a number of thoughts here:
I personally would carefully scrutinize how the load calculation was done of what your remaining capacity is. There are lots of inputs to that formula that may be easy to mess up. I call that out since if that incoming assumption is wrong it could impact what path you take. I actually don't know the formula in depth so I am unsure if you have 30 amps remaining if that is 30 amps continuous load, or just 30 amps of non-continuous load (continuous loads generally need to be sized as if they are 1.25 times larger). To do this properly you need to go inspect all the nameplates on your oven/range, garbage disposal, bathroom fans, etc... I am guessing your electrician just used some default placeholder #'s.
I actually three three possible solutions:
1a. Install a 14-30 receptacle on a 30 amp circuit. I would likely wire this with six gauge wire (assuming the lugs on the 14-30 plug and breaker would accept 6 AWG) such that you could later upgrade it to 50 amps if you later upgraded your panel (maybe leave a little more wire length in the panel if there is space to facilitate a panel swap out later).
1b. Same as 1a, but buy a second UMC to leave in the garage at all times so you have one with you at all times. Get the wall holster probably to hang it from.
2. Install a wall connector, but again, I would do this probably with 6AWG and a #10 ground using wire rated for 75c (or you could use one wire size up at 60c). This would allow you to put it on a 30a breaker for now, but then later if you upgraded your service you could upgrade it by simply swapping the breaker and changing the internal rotary dial on the wall connector. OR actually, one better would be to just put it on a 60a breaker on day one (they are typically the same price as the 30a) along with the 6 gauge 75c rated wire and then just internally set the wall connector to 24 amps still (equivalent of a 30a breaker). I believe this would meet code since the wall connector is UL approved to never pull more than what it is set at. So this way it would be trivial to upgrade later! The wall connector also has pretty granular steppings of amps it can pull, so depending on the outcome of the load calcs you might be able to set it to 28, 32, or 36 amps instead of being stuck at 24 (the limit on a 30a UMC plug) and 40 (the limit on a 50a UMC plug). So you might eek out a bit more capacity.
Also, I might get a "sense monitor" unit (look them up) to monitor your power usage and see what your house *actually* uses. This might violate code, but I might be tempted to tweak the setting up on the wall connector if I was 100% confident that my other loads were not taking me anywhere near the rated limits of my service. In a pinch you could temporarily up the supplied power with just a setting if you had depleted your battery and needed a quick recharge. Just make sure to not cook anything in the oven or stove at the same time. ;-) (I only suggest this in "jest" - you should not mess with this stuff unless you really know what you are doing)
I guess at the end of the day it all depends on how long you plan to own the house, if you have desires to add any other electrical stuff (Air conditioning, hot tub, etc...), if you think the existing panel/wiring is a hazard, etc... I personally would probably want a 200a panel and to be able to max charge my model 3 at 48 amps, but hey, that is just because I like to not be limited! I don't really need that fast of a charge for my 30 mile round trip commute...
