Home EV Charging 101

One of the greatest advantages of owning an electric vehicle (EV) is never having to stop at another gas station — apart from buying snacks or needing a bathroom break. But unless you're taking a road trip, you can fill up your electric vehicle every night from the comfort of your own home.

Now, if you don't live in a place where you can access or install an EV charger, that's another issue for another article. Here we're going to give you the rundown on home charging and what sort of setup will suit your needs. 

What exactly is an EV charger (EVSE)?

First up, there's some lingo to know. In almost all cases, the charger isn't actually the thing you are going to buy and hang on the wall of your garage or carport. The charger is built into the car.

That box with the colored lights, long cord and connector plug that you're installing is properly known as the electric vehicle supply equipment or EVSE. It's OK if you call it a car home charging station or an EV charger; almost everyone does. The EVSE is a communications and safety device that controls the charging current to keep the car's batteries from overheating. It can shut down the charger in the event of an electrical short, power surge or any other malfunction.

All EV carmakers and charging equipment manufacturers around the globe — with the exception of Tesla, which prefers to go its own way — have standardized the design of the EVSE plug universally called a J1772 connector. Tesla owners can nevertheless choose to install an EV charger with a J1772 connector because the necessary adapter is provided with each car.

Home charging speed (Level 1 vs. Level 2)

Home-based charging equipment offers two distinct levels of power that ultimately determine the speed you're able to charge at. Level 1 EV charging equipment delivers standard household outlet current at 110 or 120 volts. It provides a very slow way of charging vehicle batteries. Level 2 EV charging delivers power at 220 to 240 volts and at higher current, the same sort of power used for electric ovens and clothes dryers.

Almost all plug-in vehicles come with a Level 1 EV charging cord in the trunk as standard equipment. Never use any sort of extension cord with a Level 1 EV charging cord, even though you may be tempted by the short cord on the input end. The nice thing about Level 1 EV charging is that the cord sets are portable and can plug into any standard wall outlet, which means you can pretty much charge your plug-in vehicle anywhere you are. The catch is that Level 1 charging is basically a trickle charge that generally gets you just 2 or 3 miles of driving range for every hour of charge time.

Level 2 charging is much quicker because it's done at higher voltage and at higher amperage. But it requires beefier equipment and more robust garage wiring to handle the extra electrons and the heat they generate. Level 2 EVSE charging equipment usually costs more to buy, but there's more to be gained in both time savings and convenience. And you might actually pay less for your electricity if your utility provider offers time-of-day charging discounts for plug-in vehicle owners.

Hard-wired or plug-in?

It used to be the case that most Level 2 home EVSEs were wall-hung models permanently installed or "hard-wired" directly into the home's electrical service. Do a search on Amazon and you'll now find hundreds of listings for portable Level 2 chargers that can be plugged into a specified 240-volt wall socket. These plug-in models are more easily portable if you move, but they come with some caveats.

For one, it's recommended that you don't plug in and unplug frequently. These outlets aren't designed for that type of use and will wear out over time, potentially becoming a fire hazard. You must also be sure that the EV charger is mounted to the wall or supported in some way so it's not free-hanging because these outlets also aren't designed to support the weight of those units. Lastly, plug-in ESVEs are usually limited to indoor use since they aren't as well protected from the elements.

Hard-wired wall units are generally more expensive to install, and obviously more permanent, but they can typically carry more current (for faster charging) and are more suitable for outdoor charging if that's the type of situation you have at home.

Sizing your EVSE

Because the chargers for both Level 1 and Level 2 charging are built into the car, the maximum rate at which the battery can be refilled depends on the capacity of the charger the automaker put under the hood as well as the amount of power the EVSE can supply.

The key elements in charging speed are:

• The capacity of the car's onboard charger (kilowatts or kW)
• The voltage of the EVSE (volts)
• The amperage of the EVSE (amps)

The nominal design voltage for Level 2 charging equipment is 240 volts, but it works across a range since electrical service varies from place to place. (Sometimes it's 220 volts, sometimes 208 volts in commercial applications.) The other key element is amperage, or the capacity of the circuit supplying those 240 volts. It's probably easiest to think of volts and amps in the context of a water hose. Voltage is your water pressure, amperage is the diameter of your hose, and the water flowing through is power, in this case measured in kilowatts. All Level 2 EVSEs are built to work at 240 volts, but they are sold in a variety of amperage ratings to suit the power needs of different cars.

Common Level 2 output ratings are 16 amps and 30 amps, but there are others in between, usually spaced in increments of 8 amps and ranging all the way up to 80 amps. Which one should you buy? The short answer is you should buy an EVSE rated for the most amps your budget will allow. It may be more than your car's onboard charger is rated for, but that's no problem: The onboard charger will only draw as much as it thinks the battery can handle. Prices, though, go up in lockstep with amperage increases, both for the unit itself and the wiring necessary to support it. But when the time comes to buy a new electric vehicle, it may have a more powerful charger and you'll avoid having to buy a new EVSE to take advantage of it.

The next best thing is to size your EVSE to the maximum charging rate of the car you currently own. You can figure that out with some simple math. We'll use the Volkswagen ID.4 as an example — it has an 11-kilowatt onboard charger. Multiply that charger value by 1,000 to get watts and then divide by 240 volts to get your target amps: [11 x 1,000 = 11,000/240 = 41.6 amps]. So in order to take maximum advantage of the ID.4's onboard charger, you'd want to get a 48-amp electrical circuit.

Installation

Buying the charging station is only part of the process and cost. You'll need a qualified electrician to wire things up, and some locales require permits and inspections. An exception is if your garage already has a dedicated 240-volt plug receptacle of the proper type installed. That would allow you to buy a portable EVSE, hang it on the wall, and plug it in yourself.

For both hard-wired and plug-in Level 2 EVSEs, you'll need to install the proper-size circuit breaker in the fuse box and run wiring from the box to the EVSE's location. Then you either connect the EVSE directly or, for plug-in models, install the proper receptacle so the EVSE can be plugged in. The EVSE's specifications sheet will tell you which type of plug it has. Most are NEMA 6-50, the type used for most 240-volt garage outlets, or NEMA 10-30 or NEMA 14-30, both used for residential clothes dryers. All are pictured in this online NEMA reference chart. And in case you were wondering, NEMA is the acronym for National Electrical Manufacturers Association, which sets standards for all sorts of electrical equipment.

Costs will vary by prevailing fees for electrical work, by the amount of work that needs to be done, and the cost of any necessary permits. If the best place for your EVSE is on the interior garage wall directly behind the exterior-mounted fuse panel, there will be little wire to run and the cost could be just a few hundred dollars. If the electrician has to run wire through the wall and then 20 feet away to the EVSE location, wrapping the conduit around a corner or two along the way, it could cost hundreds more. And if your house is an older one and simply doesn't have a big enough fuse box and you have to upgrade your electrical service, you're typically talking well in excess of $2,000.

Where to buy

Most electric vehicle carmakers will have a recommended EVSE supplier, whether it's in-house or closely tied to the automaker. Some will even offer attractive charging ecosystems, like Tesla does, or offer deals, financing and installation of particular brands. But in most cases, you aren't limited to just one type or brand of EVSE, so if you shop around in advance, you'll be able to compare prices.

Some manufacturers such as ChargePoint sell direct to consumers via their websites, while many online retailers including Amazon and Home Depot sell a variety of EVSE brands. So do a little research before you commit to anything.

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