Installing a Level 2 Charger for an electric car

How-To | September 24th, 2014 by 42
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Correction: “L2 chargers actually charge 4x faster compared to L1 since power is proportional to voltage squared.” Ironically, it was easier to decide to purchase …

Correction: “L2 chargers actually charge 4x faster compared to L1 since power is proportional to voltage squared.”

Ironically, it was easier to decide to purchase an all electric Solar Orange BMW i3 than it was to decide on which Level 2 Charger to buy. BMW sells a very nice looking charger, the BMW i Charging Station, for $1,080 and as with all other chargers installation is extra.

However, it was the BMW Wallbox Pro which BMWBLOG reported on from the BMW i8 launch back in April that I really, really wanted.

I was super excited about this particular one because we have a newly installed 12kW solar system in our house and I relished the idea of being able to program where the electricity was to come from to charge our Solar Orange i3. Sadly, this fantastic device is still not available and now word on when it will be.

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So Many Options In The World Of EV Chargers

When looking at an electric car charger, it helps to know a bit of the lingo. EV nuts are very particular about their verbiage. Though commonly called a Level 2 Charger, the proper term is Electric Vehicle Service Equipment (EVSE) because the actual AC to DC conversion occurs on board the EV itself. It will be hard to break the public of the habit of calling them Car Chargers, as that’s what manufacturers call them.

Hitting on the basics of electricity supplies, in the United States a 120V is a common household plug, and 240V is what is used for household electric ovens, dryers and air conditioning units. A 240V outlet can charge an electric vehicle twice as fast as the 110V. A Level 1 Charger, which uses a household 110V current, is good when you are in a pinch – BMW even calls it an “occasional charger” so you get the hint that you need a Level 2 Charger.

When it gets to where electricity meets the EV, the SAE J1772 Charging plug is standard for all electric vehicles except the Tesla cars which have a proprietary charging plug. Thanks Elon!

Why Do I Need A Level 2 Charger?

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Level 2 charger by definition means that it runs on 240V, and can vary in power delivery.  Most Level 2 Units can charge up to 7.2 kW and pull 30 amps, and these need to be installed on a 40 Amp circuit with 8 gauge wire.

There are DC chargers too but they are 480 volts and cost around $8,000. Thankfully the Rapid DC chargers are becoming more common at commercial charging sites on the East and West coast. The DC Charger, CHAdeMO aka a Level 3 Charger, can pump a stunning 62.5 kW of direct current right into the battery.

On the BMW i3, it does require an optional $700 factory connector. I am told that this is factory installed only, if you don’t get it at manufacturing of your vehicle, you cannot retrofit it.

There are more Level 2 Chargers available than I would have thought. See our table for the most popular ones out there.

BMW i Charging Station Bosch EL-51253 Bosch EL-51254 ClipperCreek HCS-40 GE WattStation EV Charger Siemens VersiCharge VC30BLK
Amperage 30 Amps 30 Amps 30 Amps 32 Amp 30 Amp 30 Amps
Cable Length in Feet 25’ 18’ 25 25’ 18’ 20’
Output Power 7.2 kW 7.2kW 7.2 kW 7.7 kW 7.2 kW 7.2 kW
Self Contained Charging Doc Yes Yes Yes No Yes Yes
Cost $1080 $571 $737 $590 $599 $799


BMW i Charging station is 30-40% more expensive than all the other units, so it was immediately at a disadvantage. As Bosch is the manufacturer of BMW’s i Charging Station, I was immediately drawn to it. Bosch’s charger is a much smaller unit with a center holster that docs the J177A Charging Plug. The unit is available with a 18 ft or a 25 ft long cord.

The Siemens unit has a very German efficient layout while the GE one looks just like the one that Porsche uses for their plug-in hybrid cars. There’s also a very robust unit from Clipper Creek, the HCS-40 but I didn’t like the lack of contained plug doc and it’s rather unattractive compared to the other units.


The Bosch charger has a LED indicator flashing blinking green when you are charging. It also has an unit On/Off switch on the side to keep it from using any power when not in use. Bosch offers a 3 year warranty when installed by Bosch or 1 year if you do it with your own electrician.

One of the main reasons I went with the Bosch was itself contained connector dock which looks better and protects it from accidental drops. The cord also neatly stows wrapped around the unit. The size of the charger is on the small side: 16” by 14” x 5”. The BMW charging unit, on the other hand, is the size of a pay phone, if you remember what those look like.

Ultimately we elected to go with the Bosch 25’ as everything I’ve read said get the longest cord you can.

Installation of Bosch EL-51254

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Level 2 Chargers require a dedicated 40amp 240V circuit. Here is where costs for installation can be all over the map. If you don’t have enough capacity in your house, you need to upgrade the whole electric service to the house. Ka-ching!

In my opinion, you need at least 200amp service to your house to be able to add a 40amp circuit. Some older houses only have 100amp service. The second biggest cost determinate is how far you have to run the wires from the breaker box. In my case, it was about 30 feet through two finished walls and a crawl space above the garage. If you have an unfinished wall where your breaker box is, and you’re just gonna pop-out the side and place the charger right there, it’ll cost much less.


Take home lesson is: not all 240V circuits are the same. I had this grandiose plan of installing the whole thing myself, until I learned I needed 8 Gauge wire. I had planned on just using the wire from my 2-Post lift in the garage by redirecting it but this is only on a 20amp circuit. Seriously, unless you really know what you are doing, call a professional. I’ve done 110 circuits myself in the past but still called in a professional just to make sure I didn’t kill a brand new car.

NEMA 14-50

Good grief, the EV terms just don’t end.

NEMA 14-50 was not a term I was familiar before this electric journey I’ve undertaken. Anyway, it’s the way I decided to get power to my Level 2 Charging unit. The benefits of connecting a Level 2 charger this way are multiple. The biggest of which is you can simply unplug the device if you move versus call an electrician.

A bonus is when a buddy with a Tesla Model S shows up in your drive way, you can unplug your charger and have the Tesla plug directly into the NEMA 14-50. Same goes for the in-laws RV or even a welder. If you hardwire your Level 2 Charger, you loose all that flexibility. Once my electrician had the 14-50 receptacle all wired up, I sent him on his way with a check for $318.60 and I finished the rest of the install.

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In order to connect our Bosch Level 2 charger, I had to add a NEMA Plug which was not included. It cost $23 from Lowes, and can handle 50 amps. A “range” plug they call it.

How hard could it be to install? Well, it sucks!

There’s no color coded labels to tell you where to put your white/red/black and green wires in the back panel of the Bosch unit. In fact, there are only three spots for wires and I have four hanging off the plug. Hmmm. I pull out instruction manual and it says L1, L2 and N. Hmmm again. Maybe I shouldn’t have sent the electrician away.

No fear. I’ll call Bosch.

I get a someone on the phone from tech support and, I am not making this up, they say “call an electrician.” I ask, “I am on the phone with tech support for an electric car charger and you cannot tell me how to deliver electricity to it?” They answer: call an electrician. Nuts. I love the Untied States of Attorneys.


I hung up and saved my choice explicatives for the crickets in the garage. No fear, because I tapped the BMW i3 Facebook Group and rapidly got the answer I wanted. L1 and L2 are red/black, and N was green. I am just telling you what I did and electric codes could be different in your area. I had to drill out the bottom plastic section of the Bosch unit so the wires could come straight out of the bottom of the unit. It required a fancy $5 1” drill bit from my hardware store.

installing-electric-car-charger-16 installing-electric-car-charger-17

Hanging the unit was simple. A level two number 8 wood screws went into a stud to secure the metal bracket to the wall and then three torx T30 screws holding the unit to the metal bracket. Then plug the unit into the NEMA 14-50 plug. Since our BMW i3 wasn’t yet delivered to our dealer, they were kind enough to let me test drive one and make sure the install went fine. Read our experience of BMW’s 3 day extended test drive here.

There are lots of choices for Level 2 EV chargers and lots of ways to install them. This was a description of my journey which one worked for me and why. It also gives you an idea of what installation can be like. Installation charges can vary from a couple hundred dollars to over a thousand if you need to upgrade your electric service.


Bosch EL-5124 Level 2 Charger – Amazon for $792.95 including tax/shipping.

NEMA Pig tail for $23

Electrician bill of $318.60 for 40 amp circuit, 35’ of 8 Guage of wire, and labor

TOTAL: $1,134.55

See the full installation with images

42 responses to “Installing a Level 2 Charger for an electric car”

  1. CDspeed says:

    I put in a Clipper Creek HCS-60, 240V 48 amps, and required a 60 amp circuit.

    • Tommolog says:

      Nice CDspeed. I have the father of that unit, the Clipper Creek CS-60 at my restaurant which can also deliver 49amps. Chuck made a slight mistake above stating “Level 2 Units can charge up to 7.2 kW and pull 30 amps, and need to be installed on a 40 Amp circuit”. That is a common mistake because *most* Level 2 units are indeed 30 amps, but there are others like what we have that can deliver higher amperage. The i3 though is limited to 7.4kW, so it cannot benefit from the 48amp delivery like a Tesla or the new Mercedes B-Class electric drive can.

  2. Manny Antunes says:

    Nice Chuck! I’ll be installing an AeroVironment L2 charger in the coming days. Thanks to Tom!

  3. Good article, thanks. I got the same EVSE/Charger 3 months back from Amazon but with 18′ cord for under $600. IT is a good value and a good looker!

  4. Michael says:

    Isn’t that black plug next to where you drilled the hole removable so you could use it for the same purpose?

  5. DiHydro says:

    What is that black plug immediately next to the hole you drilled into your new charger? It has a screwdriver slot on it.

    • Chuck Vossler says:

      Not sure. Here’s a pic of it removed. I initially thought I could use it to route the NEMA plug into the connectors but it’s too small and at an off angle to the connectors. I tried using it but, it made the wires go acutely 45 degrees to the right then back another 45 after it got in. Then the edges are sharp brass edges when that black plug is removed. They are so sharp, they would cut insulation on wires if the plug rubs back and forth on them. Lastly it’s too small to put a NEMA plug through.

      Would love to ask Bosch but their tech support knee jerk reply to anything is “call an electrician” in the US.

      –hmm. Pic wont attach. Give me a min

      • Horatiu B. says:

        Attach a photo Chuck. It didn’t go thru.

      • DiHydro says:

        That is interesting. It definitely looks like it should a strain relief of some sort for your cable. Do you have a picture of it from the inside of that panel? I am wondering if a strain relief similar to the one next to it is supposed to thread through there. The edges, and bending the cable, would be to prevent pull out of that cord.

      • DiHydro says:

        Hey, I just looked up the documentation for the unit, and you definitely did do it correctly! One piece is missing though, you should have a PG connector strain relief on that cable. I think this is the correct one

        • Chuck Vossler says:

          The NEMA plug came w/ a strain relief which I tightened down but there’s no pic of it in article. Keeps pressure off of the wires. Agree I wouldnt install w/o it. The included one isn’t as fancy as that one though. That’s nice!

          • On The Level says:

            Great article. Others have mentioned below about the difference between the neutral (white) and the ground (green). I would respectfully recommend you have someone check the connections. If there is any 120v circuitry inside the unit, then you may have current on the neutral wire, which you may have incorrectly connected to ground.

            The ground is to make sure there is no power to the things you might touch, like metal parts (screws that hold your switch covers on for example), and it will divert a short to ground instead of through someone that comes into contact with it. You do not want to introduce current to your homes grounding and bonding components.

  6. Ivar says:

    Interesting story. It’s much the same story in Europe, the car manufacturers should really offer a service to sell and install a wallbox with the car. Selecting the charger is indeed moer complicated than the car. Also pricing varies a lot, some are twice the price for the same wallbox.

    I opted to get the second fastest options for my car, a 22KW wallbox that charges my car in about an hour. But the i3 doesn’t charge that fast anyway, so no need for that. To be honest, I could have done with a much slower charger myself, but there was a minimum amount I had to spend to get a tax deductable.

  7. goloch says:

    L2 chargers actually charge 4x faster compared to L1 since power is proportional to voltage squared. Not my intention to be critical, but to clarify than an upgrade to L2 is an even better proposition for the cost than “twice as fast.”

    • Horatiu B. says:

      That’s a good point, thank you. Glad we can learn something new.

      • Jason Burroughs says:

        can you please edit the original post to reflect that it had an error? You should not have to read the comments to discover that a critical number was off by half!

        • Horatiu B. says:

          We just added that. Thanks

          • William says:

            I don’t think this is correct, actually. L2 chargers are more than twice as fast as L1, not because of “voltage squared”, but because they also up the amperage. That’s not a requirement, but it’s almost universally true in practice.

            The standard 120 volt circuit in the U.S. is rated for 15 amps (as represented by the NEMA 5-15, the most common receptacle by far), and that’s shared among several outlets. So L1 chargers only draw in the range of 8-12 amps — 16 amps in the extreme case (don’t do this unless it’s a 20 amp circuit).

            But on the 240 volt side, you typically have dedicated runs (only one outlet on the circuit), with wiring and breakers rated for much higher amperage. For example, the receptacle you used here, the NEMA 14-50, implies a 50 amp breaker (and wiring to match). So common L2 charging rates start near 16 amps, and go up to 32, with a few cars able to do up to 40.

            With my own car, for example, the bundled L1 charger does 8 amps, while the car will draw 13.75 amps from L2 (AKA 3.3 kW, a common rate). So, combining the voltage and amperage multipliers, it would be 3.4 times as fast. And actually it’s even faster, because there’s a substantial fixed draw — it ends up being nearly 4x altogether. (The manual says 22 hours on L1, and 6 hours on L2, which is pretty accurate.) But note that at no point do I square the voltage to account for these numbers.

  8. Conrad Steinweg says:

    I believe you should have connected the white wire, not the green. White is tied to the neutral block in the main panel and green goes to ground. Ground and Neutral on bonded in a main panel, but it’s just something to avoid confusion later. Especially if the circuit is transferred to a subpanel later where ground and neutral are not bonded. I just bought this same unit. Have the parts, just haven’t done the install yet.

    • Felipe Garcia says:

      Chuck did the right thing by using the green cable. according to page 4 from the install manual that is a ground cable. I am in the process of installing the same charger. Great article Chuck. A closer pic of your circuit breaker box and the new breaker would be cool ;-)

      • Conrad Steinweg says:

        Hi Felipe, I would strongly suggest you consult an electrician first. The guy that put this charger in didn’t even know what L1 and L2 meant or what a NEMA 14-50 outlet is. Take a look at the picture on his wires hooked up to the back of the charger unit. Notice how the green lead is smaller than the black, red and white leads. Use a ruler right on your computer screen to see it. Some 50-amp pigtails have #6 for the L1 L2 hots and #8 for the ground and neutral, some have #6 for the hots and the white, with #8 for the ground (green). In a 4-wire 240 volt circuit, green is ALWAYS connected to the ground block. White is ALWAYS connected to the Neutral block. The neutral block is the primary ground for all circuits in the house and is connected to the utility grid neutral. Green is the backup that goes to the grounding rod outside your house, they just happen to be bonded in main panel only for additional safety. NOTE: The manual was written in China. Ground could be a misplaced term. When you wire a 240 circuit in THREE-wire, you use the black, red and WHITE. Not green. If you are powering yours from a subpanel, please consult a pro. Green wire in subpanels back to the main panel can be smaller than the white. So is your ground wire in your main panel. Take a look. Just trying to make sure everyone understands where these wires go to in the panels and what standard code is. These cars pull a steady 30 amps and need everything perfect. Every nut on stranded wire should be tightened several times while wiggling the wire to make sure there is not arcing over time due to loosening. Hope this helps.

        • Felipe Garcia says:

          Thanks Conrad , i will of course double check with a sparky friend of mine for code and configuration.

        • taylorlightfoot says:

          If only three wire connections are available on the charger, you should connect the two live wires (Red & Black) to the L1 & L2 (Doesn’t matter what order those two are connected when connecting them to the L1 & L2 terminals. The remaining terminal will be your neutral terminal and the neutral (White Wire) should be connected. If there were four terminals, then the ground would have a marked terminal. If the charging stations housing were metal, you should connect the Ground (Green Wire) directly to it if it doesn’t have it’s own terminal.

      • bbmertz says:

        Thanks for this informative article! I just installed the Bosch EVSE using these wiring instructions and it works great with my BMW i3.

  9. Denys Allard says:

    Chuck, provided the physical room exist, the only difference with the fastcharging port is the addition of 2 more contacts which are wired directly to the batterypack. As for the price, I assume your referring to the REMA product which was originally $700. but now is $800. I am an electromechanical engineer; my company makes the J1772 combo connector (for a lot less) and we also do EV conversions. I am looking into the possibility of a retrofit. OR

  10. TommyT says:

    FYI, The universal codes for wiring are this L1, L2 and L3 for 3 phase mean Line, which are the hot lines. N means neutral. G mean ground. Neutral and ground are really about the same, but should be separated because feedback on the neutral line can screw up some electronics elsewhere in the house or building. When you have 4 lines on a 240V it means there is both a Neutral and ground. This is usually not necessary. Your electrician probably installed the ground because you didn’t have the charger and he wanted to make sure you had it if you needed it.

    The reason Bosch told you to call an electrician is because they assumed that if you didn’t know what L1, L2 and N meant, you probably didn’t know much about electricity.

  11. Kristin says:

    Hi Chuck,

    Your article is super-helpful. Thank you!

    Question: I read above the recommendation to add a NEMA 14-50 plug-in option (so that one could, “unplug your charger and have the Tesla plug directly into the NEMA 14-50”). This is what I’d planned to do and then I found this new Chargepoint charger: – ChargePoint Home 25: 32A Plug station with 25′ cord.

    After reading your post I asked in a forum: “if I want my electrician to install it with NEMA 14-50 do I get the hardwired or plug in?” and someone replied: “These units are not 14-50, unfortunately. you’ll have to change the plug to 6-50. Otherwise, he will have to hardwire it.”

    I’m confused — do I buy the hardwired or plugin version and if I buy the plugin, do I need to have my electrician do anything special to be able to (as you mention in your post) “unplug your charger and have the Tesla plug directly into the NEMA 14-50”?

    I greatly appreciate your advice!

    • Chuck Vossler says:

      IMHO if it’s this hard for them to install the NEMA 14-50 and the Chargepoint charger you want, I would just have them install the Chargepoint and punt the 14-50. Tesla sells an adapter that you can use on the end of your Chargepoint Charger that will fix this and those J1772 Adaptors come w/ all Teslas. If you are missing it, Tesla sells one for $95.

      • M Oczakow says:

        Yeah, its funny people start bad mouthing at Tesla before they even bother to check their site if they have adaptors. The only thing that does that, is to display their ignorance and bias.

  12. StefanoR99 says:

    If you live in the bay area these guys are great at installing level 2 chargers, check out

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