Charging at Home Question

Charging at Home Question


So my house needs a electrical upgrade before i decided to buy a tesla.

My questions is, with out the HPWC Tesla offers the best charging option you can get at home is 240 /40a correct ? i ask because i was playing on Recargo and i say a home user said he had 240 /70a, could have been a typo or he may have meant the HPWC.

gimp_dad | April 26, 2013

Yes. J1772 supports a range up to about 70 or 80A. So does HPWC. If you install a 50A circuit with HPWC you will get 40A charge rate (equal to NEMA 14-50 or 6-50 plug with UMC). Anything capacity you can have beyond that (up to 80A charging with 100A circuit) could be properly handled by an HPWC.

shop | April 26, 2013

No, he meant the Roadster charger. For a Model S, just install a 50A breaker, 50A wire, and a NEMA 14-50 plug. The car will charge at 40A by using the supplied Universal Mobile Charger you get with the car.

DTsea | April 26, 2013

if you put in 50A circuit dont bother with HPWC or dual chargers, the NEMA 14-50 is far cheaper and the single charger is fine. Charges 30 mi/hr. I use it and it works fine.

models60 | April 26, 2013

I use NEMA 14-50 charger at home with 50 AMP circuit and is more than adequate. Charges at about 31m/hr so between 12:00 AM and 6:00 AM (PG&E E9 off-peak), the car is fully charged.

darobin77 | April 26, 2013

Ok, sorry for the newb questions. im diving into the deep end here was all the info (wish this form had a search function)

So is the NEMA 14-50 a aftermarket charger i purchase or is that just a plug / outlet that i have my electrican install ?

And if this option works best by census why would one need twin chargers ?

Longhorn92 | April 26, 2013

NEMA 14-50 is just an outlet that an electrician can install - the charger(s) are located in the car with the Model S.

You only need two chargers in the car if you have more than a 40A outlet (50A breaker as with the 14-50 outlet). The HPWC provides 80A continuous (100A breaker), so you would need twin chargers in the car to use the benefit of the HPWC.

David Trushin | April 26, 2013

One person i saw on the thread said that the hpwc would be useful if you drive the battery down during the day and wanted to go out in the evening.

shs | April 26, 2013

A NEMA14-50 is an outlet that you would have an electrician install, very similar to one for a dryer in your laundry room. The Tesla comes with a cable that will plug into that outlet and the car. You won't need twin chargers to charge at home, or at Superchargers, but I had the twin chargers installed as there are several public chargers in my area of central California that will allow charging at 70 amps, if and only if you have the twin chargers. These chargers will still work with the standard single charger, but more slowly.

RacerX | April 26, 2013

Very good and concise answer

Brian H | April 26, 2013

There's a search helper site a user here built, .

RD7 | April 26, 2013

FYI, basic electrical code dictates that you cannot supply more than 40 amps to a detachable cord. Circuit breakers are always rated higher than the expected load (which is 80% of the breaker rating, so 0.80 * 50 = 40). No matter what you do, you cannot stay within code and have more than 40a delivered. That is one reason why the HPWC has a dedicated cord - this is a code requirement.

You can set the HPWC to deliver as much as 80 amps if you have a 100 amp breaker and wiring (I think it is 3 AWG copper or 1 AWG aluminum, but best to have your electrician check). Of course, the current HPWC breaker problem will probably limit you to 60a for now, but I have been able to charge at 80a with no problems since I have very clean power.

shop | April 26, 2013

For most people, a NEMA 14-50 installed by an electrician is more than enough. A few people use their cars so much during the day, that they occasionally want to fast charge before going out in the evening. Think a salesman in Los Angeles. In that case an HPWC would be useful.

bp | April 27, 2013

For overnight charging, 14-50 is enough to fully charge the car.

But if you do a lot of driving in a single day - and need to do a quick charge - the HPWC is useful.

Before the HPWC arrived, I was having second thoughts - but when I needed the quick charge, was glad I had it.

golftoday | April 27, 2013

I have a Nema 14-50 in my garage and it's more than adequate. I had a Nissan Leaf (80-100 miles range) for 21 months with a J1772 that charged at 15 miles/hour, and only twice in 21 months did I need it to charge faster. Maybe I need to get out more :)

jat | April 27, 2013

Back to the original question, you can buy >40A J1772 EVSEs for your home, but you will find they cost more than the HPWC and are less convenient so there isn't really any point unless you have another EV you want to charge on them that only takes J1772. Even then, it will be inconvenient to share them (we have a separate J1772 charger for my wife's LEAF).

If you never care about charging fast, such as when you get home after work and want to head out of town where you need the full range, then even a 30A dryer outlet is plenty.

@rd_redford - the 80% factor comes in because any load for more than 3 hours is considered a continuous load, and requires derating the breaker/wire if they aren't designed for continuous load. For non-continuous loads, you can use 100% of the wire/breaker rating.

djm12 | April 27, 2013

Two days ago, I could have used a faster charge rate. Doesn't happen very often, maybe two to three times a year.

darobin77 | April 27, 2013

Thanks all. This electrical stuff is confusing to me but i think i got it, the help here and a some more reading i think i am all set. Im getting a 60kWh, I have a 110 outlet behind my parking spot at my office so hopefully it will be rare ill need faster charging. 30miles per hr.

Electrician is already scheduled.

Taking my old car to CarMax today to hopefully sell it for a nice down payment and the reservation will be released from hold !!!

murraypetera | April 27, 2013

Things to think about when you order and before you have outlets installed.

The cost of running 50 amp vs 100 amp cable is very small ( $200-$300 depending on how far the run is )If you ever choose to upgrade to HPC you will need to re-wire.
The cost of the twin charger when you order is $1500 but $3600 later.
The cost of the HPC is $600 more than a second mobile connector. I think most people will want to keep one in the car and one in the home. I decided the extra $2500 was worth hedging my bets having ordered a 40kwh for the ability of a quick top off.

jat | April 27, 2013

@darobin77 - just to make sure, you will *not* get 30mi/hr charging on a 110V outlet at work - that is using a 14-50 or 6-50 outlet.

darobin77 | April 27, 2013


Yes i understand, Just meaning by the time i get to work and using the 110 i should be full and when i leave the office. When get back home the Nema 14-50 should suffice most days. @murraypetera thanks for the info on pricing after the initial order.


Sudre_ | April 28, 2013

I agree with murraypetera on the running 100 amp cabling rather than the 50 amp.... actually I installed a 100 amp panel because I plan on getting my wife a Tesla GenIII when they come out. With the 100 amp panel in the garage I can always add another 14-50 when we get her car.