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240 Extension Cords

Sorry if this is a duplicate, but I searched this forum and didn't find a thread like this.

I know that Tesla says not to use extension cords, but I just returned from my first road trip (90 mi each way) and I almost got stranded. the place I stayed had a great 240 plug near a parking spot, but it was just about 15' beyond the standard charger that comes with the car. So, I moved to another spot where I could use their 110. that worked fine, but at only 3 mi per hour, I needed over 24 hours to recharge the "90 miles" that I had driven which drained my engine 140 mi equivalent (4 guys in the car and it was cold).

I don't want to have that "range anxiety" again, so I would like to find a 15' - 30' extension cable that will get me closer to the 20-25 mi/hr charge rates that I get at home.

I saw that one guy bought this RV extension cord on Amazon, but he didn't say if it actually worked and charged in that low 20 mi range.

Anyone have experience with this or another RV extension cord and if they will work for occasional (5x per year) travel?

That should be fine.

The Model S is supposed to be capable of sensing the use of an extension cord and refuse to charge. If the extension cord is appropriate for the job it might not sense the extension cord and let your charge. The shorter the run the better. I think that you can find a cord in 15' lengths.

FlasherZ at TMC is the expert on such matters. You might try a search there.

I have the 15' Camco extension cord from Amazon, because I'm too lazy to back my car in. It works fine - I'm getting 20-25 m/hr. I don't know about the 30' one though.

I bought the 30' one and used it as a test to test a dryer plug (240v, 30a). It worked fine. Tesla can only tell if you are using an extension cord if it senses a large enough voltage drop when it ramps up the current. And that will only happen if you use an undersized extension cord. Those rv extension cords are sized correctly for 50 amps, so no problem.

I purchased a 15ft 50amp extension cord from Camping World. I brought it to the Tesla service center in Chicago. They tested it and it worked fine.

@Captain_Zap - wires in the wall vs wires in an extension cord are no different as long as they are of sufficient size for the current. Theoretically, you could use TDR (time domain reflectometry) to see the slight impedance mismatch at the plug and tell there were two plugs, but it would be extremely hard to distinguish that from a splice in the house's wiring.

Instead, I am sure all the car and/or Mobile Connector cares about is that the voltage is in range and perhaps measures the voltage drop as the current changes, so it could detect that your wiring was insufficient for the current, but even that is a stretch.

Many people use extension cords insufficiently sized for the current, and the car carries a continuous load so heat has a chance to build up. Even running my leaf blower for half an hour, an extension cord rated for 15A gets pretty warm.

I own, and tested the very exact extension cord cited in your post. It works fine. Charges fine. No problems.

This exact extension cord has been posted many times on this forum, no problems reported.

Yeah, it might work, but there's no way that you need 240 of them.

@Jat - TDR - wow. That takes me back. Running 10-base-2 cable back in the good ol' days.

I made my own 30A NEMA 14-30 extension cord using parts picked up at my local ACE hardware store. Since the wire is rated at 30A I have had no problems charging. I would have to back into my garage as well in order to reach my outlet but the 20' extension cord is working like a champ.

The only issue I had was I went to a friend's house and all of their 220 outlets were NEMA 14-30L and Tesla doesn't offer any L adapters. I may need to make one, though I found some on Amazon that go from a 14-L30 to 14-50.

shop | MARCH 20, 2013
I bought the 30' one and used it as a test to test a dryer plug (240v, 30a). It worked fine. Tesla can only tell if you are using an extension cord if it senses a large enough voltage drop when it ramps up the current. And that will only happen if you use an undersized extension cord. Those rv extension cords are sized correctly for 50 amps, so no problem.

shop, how did you get the 30a dryer plug to fit into this Nema 14-50 cord? I'll appreciate it if you could elaborate. Thanks.

@nvjx, I made myself an adapter. It was a fun little project and I actually used a couple of the adapters I made on a recent trip. I made the following document that you can use to make your own adapters until Tesla makes more of them available.


I use the 30' camco RV cord every night with my Tesla, my plug is 25' from my driveway. No problems, works fine.

Thanks shop.

I have a custom 50' 14-30 extention cord using 4-wire 8-guage outdoor cord (you can sometimes find it at Home Depot for a few dollars a foot); never any problem charging at 24A from electric dryer outlets. Also have a 100' 120V 12-guage extension cord that I've dropped out of hotel windows to hold a charge overnight in cold weather. It usually works okay at 12A, but in some situations I've had to reduce the current to 10A or 8A to keep the car from shutting off due to low voltage.


The last time I was at the local tesla store (dania beach, fl), they were using extension cords to charge their cars. If it's good enough for them.....

All depends on the gauge and quality. Jack, the low voltage shows the cord is over-stressed. Such stresses can produce cumulative damage, then overheating, then fires. Caution.

Great guide Shop!

Personally I would not use a 12-guage 100' cord for 12A, 120V. You need 10-guage for that.

@Shop: Thanks for the detailed guide, great job!

Shop, your adapters look to be excellent quality. I don't think mine look as good but for those who are building up a set for the first time they might want to consider 6-50 as their main target for their UMC plug. It avoids messing with the 14-50 neutral and allows for a bit lighter extension cord (a NEMA 6-50 welders' cord only has three conductors instead of the four found in a 14-50 cord).

Because I was lucky enough to talk Tesla out of both 6-50 and 14-50 adapters back in Aug when I took delivery, I had the choice of which type of extension cord to choose and hence what type of adapters to make. I settled on 6-50 for the above reasons.

And, as many have already mentioned, be paranoid if you make any of these adapters. Some of them can be dangerous even if you wired them up exactly as described.

Tesla will not offer the adapters Shop made, as Tesla does not want the liabilities. For those who want the extra length, the only choice is to make your own.

Should be no problem as long as the gauge of the cable is close to the same as what you have in the wall (e.g. #8 for 14-50). Of course the cables have ratings so that should be sufficient to consider. The thinner the copper, the more voltage drop you get and the more heat will radiate from the extension cord and won't be charging your MS. The longer you run a cable the thicker the copper should be also.

@Hills not sure who you are responding to but I was pointing out the option I chose which was to make the adapters Shop made but with the "other" end being 6-50 rather than 14-50. I have pigtail adapters for
10-50 to 6-50
10-30 to 6-50
L14-30 to 6-50
14-30 to 6-50
14-50 to 6-50
6-20 to 6-50

Thus, given any outlet that I list on the left side of the above list, I can connect through my 50' welders' extension cord to my UMC. The welders' cord is made with 8-guage wire and one less conductor helps its size and weight.

Also, Tesla has already started offering the 10-30 adapter for the UMC which is one of the "controversial" ones since it is effectively tying neutral on the outlet to ground on the car end.

The issue is that you don't want to carry a whole stack of extension cords with you for that rare case where you are stuck and need to charge from some outlet that you can't get close to. The pigtails plus extension cord solve that problem.


Is there a reason why you didn't build a 5-15 to 6-50 pigtail adapter? I'm thinking of picking up an extension cord to use with the supplied NEMA 5-15 adapter (I'm heading in the next few days to a resort cabin that has an outdoor 110v outlet). I was hoping I might be able to get a heavier cord that could then also be plugged into a 240v outlet, using an adapter? For example, could I get an RV or welder extension cord, and then buy or build an adapter to use that cord with a 110 outlet.

On the other hand, since I haven't seen such an adapter for sale and I don't think I could build one before I leave, I'll probably just get a 110v cord.

@gimp_dad, yeah, that makes a lot of sense to use the 6-50 instead of the 14-50 as your base adapter. Just didn't think of it.

The trick is to find a nice receptacle for the 6-50. Because they need to look nice :-)

Oh, but thinking about it, I don't know if the 6-50 adapter into the tesla would accept a 120v adapter. I notice that gimp_dad's adapter set does not have a 120v one. You would have to test it out. Also, of course, the 14-50 comes with the car, and you'd have to purchase a 6-50 adapter from tesla...

@shop - yes, that was my concern. I had assumed, looking at gimp_dad's list, that the 6-20 adapter was 120 V (because it's 20 amps), but I just looked it up, and it is rated for 250 V maximum. So if the car sees a 240 V connection, it probably won't work to plug into a 120 V outlet, even if you dial back the amps. I was hoping to carry only a single extension cord, but that's probably not possible.