Is Nema 10-30 less efficient?

Is Nema 10-30 less efficient?

Silly question...

According to the adapters page at, The 10-30 (that is for my dryer, that isn't being used because we have a gas dryer, but I'm assuming works fine) already in my garage charges at roughly 22 miles range / hr. The 14-50 would charge at 30.

So, a few questions because I don't know electricity all that well. I'm guessing to charge 50% (30-ish kw) would use 30kw, and would cost me 30kw on my electric bill, and the only difference would be how fast that happens, right?

My dryer on the main electric panel has 2 connected 30's, and sharpie says 220, I'm guessing that is a 220v instead of a 240v? Does that mean it won't work?

Just trying to figure out if I can use what's already available or if I need to install the 14-50.


Bighorn | 2019年3月16日

10-30 works great. 220 and 240 are the same thing. Efficiency is comparable

lunde | 2019年3月16日

We had a NEMA 14-30 outlet installed, and it is equivalent to L2 charging stations. We get 21 miles per hour of charge.

Frank99 | 2019年3月16日

You're fine - your car will charge slightly slower on a 10-30, but the charge efficiency should be about the same as a 14-50. Charging from 0 to 310 miles of range will take about 75 kwh either way - the 10-30 should take about 13 hours, the 14-50 about 10. If you drive less than 300 miles a day, either one will easily charge the car overnight.
It's possible that your house has 220V, but most likely it has 240V. The car's charger couldn't care less - it's compatible with 120V outlets, 208V outlets, 240V outlets, 277V outlets and everything in between. Plug it in and go.

chadbobb | 2019年3月16日

This is an old post but where I did some math for 120VAC charging. Posting here for reference

120VAC is only about 50% efficient.... you're using 2kWhr to put 1kWhr into the batteries. It's not just about range or charging miles per hour. You're literally wasting electricity. You're now above what an ICE engine uses in fuel.

For every dollar you spend charging the car, you are spending a dollar to not charge the car.

There is a fixed power load to run some of the charging and cooling pumps. There is a dynamic charging load based on the charging circuit.

Let's make the math easy. Let's say 1000 watts is available at 120vac and 10,000 watts at 240vac (8.33A and 41.6A)

Let's only consider the fixed load and assume it's 500w.

@1000w. 1000-500=500
500/1000 = 50%

@10000w. 10,000-500=9500

The real numbers aren't far off. .8*15A = 12A. 12A*120V = 1440 Watts. About 750watts to run the cooling circuits and pumps and major initial losses of the charging circuit. leaves about 690watts into the batteries.... works out to about 3MPH too. 48% efficient

240VAC @ 32A = 7680 watts.
leaves 6930 into the batteries. 90% efficient.

chadbobb | 2019年3月16日

Circuit 5-15 10-30 14-50 Wall Charger
Volt 120 240 240 240
Amp 15 30 50 60
Actual Amp 12 24 40 48
VA 1440 5760 9600 11520
Wasted VA 750 750 750 750
47.91666667 86.97916667 92.1875 93.48958333

From Excel.... Not spending the time cleaning it up. Final Answers are

5-15 = 47.91666667%
10-30 = 86.97916667%
14-50 = 92.1875%
Wall Charger = 93.48958333%

jeff d | 2019年3月16日

Wow, just typed a whole long response only to get a no permission error... frick.

Let me summarize, like chadbob said there are rules and he's got it all but with lots of extra info.
If you want to use the 10-30 (30 means 30A) you need to have a breaker that's >38A (40A). if it's a 30A breaker you need to be sure to tell the car to not exceed 24A. The car may not do automatically detect this, so you should confirm.

Looks at the HPWC ratings for the model 3 you can see that the LR needs a 60A breaker because it will charge at close to 48A, while charging the MR/SR at 32A because the breaker is 40A. NEC rule, current can only be breaker/.8. If your in Canada or somewhere else do whatever no one cares.

Is the dryer hookup in the garage within 25" of the car's charge port? You don't want to use any kind of extension cord unless you have some marshmallows you'd like to toast. There are extensions for 10-30 but they are expensive, and you still need to be sure of the power ratings.

chadbobb | 2019年3月16日

10-30 is only rated for 30A and therefore requires a 30A breaker or smaller. 38A breaker is not is not allowed.

10-30 should charge at 24A

SysConsultant | 2019年3月16日

Jeff d - When you mentioned that the M3 needs a 60A breaker and it will charge at 48A, that's likely to confuse some readers because it needs to be qualified further.

Yes, the M3 will accept a 48A charge but only from a Tesla WALL CHARGER on a 240VAC circuit. That circuit will require a 60A breaker and associated direct wiring due to the NEC rule about de-rating a constant load to 80% of the circuit breaker rating.

But in the case of the Tesla MOBILE CHARGER that comes with the car, the maximum charge current is 32A@240V and that requires a 50A breaker and associated wiring/receptacle. Typically this is either a NEMA 14-50 Receptacle or a NEMA 6-50 Receptacle. Either will work exactly the same for charging your Tesla. Your M3 won't try and won't be able to accept any more than 32A with the Tesla MOBILE CHARGER. This is true even if you set the charge limit to 48A and install a 60A breaker.

I hope that helps...

Frank99 | 2019年3月16日

The Tesla High Performance Wall Charger (HPWC) DOES NOT REQUIRE a 60A breaker. It can be installed with a wide range of circuit ampacities, from 15 amps to 100 amps. Upon installation, the electrician will configure the HPWC for the circuit ampacity, and the car will change it's charging current appropriately. A 60A circuit will maximize the charging rate of the Model 3, but certainly isn't required.