I was confused about what I’d need for a charger at home for my EV. It’s far simpler than I realized. Lots of notes here specific to North America. Simple summary: get an electrician to install a new 50 amp circuit with an NEMA 14-50 outlet on it. Then use your car’s provided charger or buy a high quality charger like a Chargepoint Flex or an Emporia for about $500. You’re done.
Here’s lots of detail I’ve learned in the last week or two. Shoutout to Reddit /r/evcharging and in particular this wiki page and this post. They have useful if opinionated info.
How AC charging a car works
I’m only talking about Level 1 & 2 charging you do with AC power from a wall outlet. I’m ignoring Level 3 charging: that’s high power DC stuff you’re not doing at home. With AC charging everything from the wall outlet to your car plug is just to supply AC power to your car. It’s mostly just a wire; all the fancy stuff is happening in the car itself. The thing we call “a charger” on the wall with the plug is doing so little that “charger” is not really the right word. The Reddit nerds prefer the term “Electric Vehicle Supply Equipment” (EVSE).
Most EVs today use a J1772 plug that is carrying +120V, -120V, and ground to your car. It’s mostly a fancy extension cord. There are also two signal wires: one is used to detect that the cable is plugged in, the other is a simple protocol that tells the car how many amps max it can draw from the charger. Providing those signals is the only extra necessary thing an EVSE is doing.
Tesla has a different plug, the NACS plug. And starting in 2025 all North American EVs will use this plug instead. I don’t know details but NACS is enough like a J1772 that adapters are simple and cheap. During the NACS transition we’re going to be using a lot of those adapters.
Note that EVs have a charging curve: batteries charge slower and less efficiently the more full they are. Details are complicated and vary by charging source and car type. But all EVs charge better up to 80% or 90%; that’s part of why they all recommend not charging to 100%.
Level 1 and 2 charging
Level 1 charging is powered via a plain old plug, 110V AC and an ordinary NEMA 5-15 outlet providing 15A maximum (12A in practice). That gets you about 1.3kW and will take about 3 days to fully charge a typical EV with an 80 kWh battery. Everyone scoffs at how slow this is but can actually be useful if you’re charging in your garage and don’t drive much. Don’t write it off entirely!
Level 2 charging is also powered by a plug or can be hardwired. It’s higher power: 240V AC and often a 50A circuit. These high power circuits use a special plug. A NEMA 14-50 is common and typically will get you about 9kW, that 80kWh battery can be charged overnight. If you already have a 240V circuit in your house you can still use it even if it’s lower power or a NEMA 6-50 outlet. Level 2 is what people install in their homes.
Installing a power circuit
Unless you are lucky you probably need to install a new circuit in your house and that will require an electrician and maybe a permit. Go ahead and install a 50 (or 60) amp circuit, it won’t cost much more. And install a NEMA 15-50 outlet for the extra neutral wire. All this takes a few hours. I had no problem adding a 50A circuit to my 100A house power supply but houses with funky wiring, who knows.
The folks on /r/evcharging prefer hardwiring instead of a socket. It eliminates one point of failure, the need for an outlet, and possibly a GFCI breaker. On the other hand it means you need an electrician if you ever replace your charger, or at least do some tricky wiring. I chose the plug. Also there’s a question whether the common Leviton 14-50 outlets are up to the task of continuous high power draw for EV charging. I decided it’d be OK.
One weird thing is that for continuous loads, you’re only supposed to go to 80% of maximum rated power. See here or here for details. A 50A circuit should only actually have a 40A charger plugged into it. That 14-50 plug is also max 50A, so plug-in chargers stop at 40A. Hardwired will go to 48A because the plug is not a point of failure, although you will need a 60A circuit and breaker for that.
Choosing a charger (EVSE)
The EVSE does so little it seems unnecessary to spend a lot of money on one. Your car probably came with an adequate one and it may be all you need. The main distinguishing factor of particular EVSEs is a bunch of fancy scheduling and tracking software which are really not necessary. Your car probably can schedule charging itself. The tracking is not terribly interesting.
However: that charger is in your house. With a lot of power passing through it. This is not the place to cheap out on dodgy goods. Amazon is full of generic $200-$250 level 2 chargers that are not UL certified. They probably work fine but what if they set fire to your house? In the end I decided to pay more like $400-$600 for a trusted brand with UL certification. Almost all of them come with fancy software which you might then just ignore.
The evcharging wiki has a good set of recommended charger brands. I narrowed it down to three that had a plug version and were available on Amazon: Autel, ChargePoint, and Emporia. All UL certified, $400-$500 (on sale), well reviewed on /r/evcharging. I also liked the look of the Flo dumb charger but it’s hardwired only.
In the end I chose Emporia, mostly because it was the cheapest. And while I think the smart options are superfluous Emporia has an interesting suite of smart home electricity products. Including an energy monitor and a way to schedule the car to charge when your solar system has surplus power. I’m not using any of that now but I liked what the company is doing.
Conclusion
In the end it’s pretty simple to set up an EV charger at home. Running the circuit is the only hard part. You know what’s great? Never waiting in line at a gas station again. Having your car fill itself up every night when parked at your house.