Charging Your Tesla At Home

Charging at home is central to your ownership experience–it will be your primary method of charging your car and starting each day with a full tank is one of the perks of EV ownership. Most of this section is for folks who can install their own charging equipment. At the end, I’ll discuss options for apartment dwellers.

How fast can I charge?

The first thing to determine is how fast your car can charge and the size of the electrical circuit you will need. This table covers the charging speed of the of the current Tesla models and the size of the required electrical circuit. For other EVs, you can get similar information from your manufacturer. In the US, an electrical circuit needs to be sized 20% larger than the size of the charger, so a 48A charger needs a 60A circuit.

Note: charging speeds assume you are seeing the ideal maximum voltage (i.e. 120V or 240V). This is almost never the case–there are many real-world factors, including distance from you panel, that will reduce the voltage that your charger sees, and, thus, the actual charing speed you will see. For example one of my chargers is literally on the the other side of the wall from my panel and my charger still only see 237-238V.

Find an Electrician

The first thing to do is find a good electrician–ideally you want someone who is licensed and has experience installing EV chargers.  Tesla offers a Find an Electrician webpage,  but some owners have reported exorbitant pricing through this service, so be aware.  Other places for references through online communities, Tesla or EV clubs and though sites like Yelp. If you don’t have a strong lead on an electrician have two or three come out and offer quotes. The electrician will give you three important pieces of info:

1. Whether you have physical space in your breaker box service panel.  If you do, cool, if you do not, the electrician might be able to consolidate other circuits or may recommend a sub panel.
2. How much spare electrical capacity you have.  Ideally you want to be able to support a 50 amp circuit for your car charger.  Determining if you have the capacity is more than just adding up the breaker values currently in your box  and subtracting from what your panel supports.  Instead, ask your electrician for a dynamic load analysis (if they look at you quizzically, call another electrician). The analysis will give you a better idea of how much spare capacity you have, which will determine how fast you can charge. For example, I have 200A service, but can still charge both our cars at one time, because we charge at night when there is little else going on.
3. How much it will cost to install your charger.  This is where it is useful to get multiple bids.  You will need to have an idea of where you are planning to park your new car.  Distance from the breaker panel and intervening obstructions/complications will drive up the price of the install.  It is worth asking the electrician if there are any changes you could make to the proposed location the would help lower the cost.  The bottom line is closer is better, both in term of cost and charging speed.

If you already have a favorite electrician that might not be up to speed on EVSE installation, refer him/her to NEC Article 625, or the equivalent for your country.

Charger 101

Every EV supports AC charging (i.e. from an outlet) and includes an AC charger onboard that takes the AC current from the plug and converts it to DC to charge the battery. What most people call the “charger” is technically called an EVSE (electric vehicle supply equipment) and is more like a really smart extension cord–its role is to allow you to connect your EV to your electric supply and enforce safety protocols to make sure charging is completed in a safe manner.

With DC fast charging or “Level 3” charging like Supercharging or CCS, the chargers are external to the car (look for the big equipment cabinets at the location) and they connect directly the the battery in your car and bypass any internal chargers–there is more info on L3 charging in Charging Your Tesla on Trips.

Electrical Outlet + Mobile Connector

Tesla sells a modular EVSE called the Mobile Connector which comes with a NEMA 5-15 (the 120V outlet you know and love) adaptor. The “modular” part is that you can buy additional adaptors for other kinds of outlets if you decide to upgrade your home charging or want more flexibility while on the road. The Mobile Connector used to be included with all new cars so it was the simplest and least expensive solution. Now the Tesla EVSE must be purchased separately, so it might be worth considering 3rd-party EVSEs (see below).

While 120v is ubiquitous, the downside is charging speed. With 120v, the you can expect to add 2-3 miles of range in an hour. If your daily mileage is 30 or 40 miles, this can work, the only gotcha is if you go on a long trip, it can take several days to re-fill your battery.

Ideally, you want 240V charging as it can add 20-30 miles of range per hour to your car. You may already have a 240V outlet in your garage, for example for a clothes dryer. This table can help you identify an existing outlet (if in doubt, call an electrician):

If you are starting from scratch or want faster charging speed, this table will help you identify available adaptors for the UMC and the charging speed you can expect. Ideally, you want to get a NEMA 14-50 outlet if your panel can support it (no one has ever complained about charging too quickly):

Finally, some owners will buy a second mobile EVSE specifically for home charging and leave the original UMC in the car. The primary reasons to do this are so you don’t accidentally leave the charger at home to to minimize wear and tear on the outlet and plug from daily plugging/unplugging.  Info for your electrician.

Tesla High Powered Wall Connector (HPWC)

This is Tesla’s hard-wired EVSE.  Owners will opt for the HPWC for some combination of following reasons:

1. They are looking for faster charging option than the UMC offers–the HPWC will add up to 44 miles per hour
2. They like the aesthetics of the HPWC
3. They don’t want to deal with constantly plugging/unplugging the UMC
4. The have multiple Teslas–you can put multiple HPWCs on the same circuit and they will automatically share it

Actual charging speed will vary by the capacity of the circuit and the model of car:

 Info for your electrician.

Note: Older Model S could charge at up to 80A with the dual charger option and older Model X could charge up to 72A with the high speed charging option.  If you have just purchased an older model and are are unsure how your car is equipped, Tesla Service can enlighten you.

3rd Party EVSE

You are not limited to Tesla-branded charging options. There are a number of reputable companies on the market, like Clipper Creek, for example, that make EVSEs that will work with your Tesla and the included J1772 adapter (details on this in Charging Your Tesla on Trips).  If you have EVs from different manufacturers, this is often a good approach, especially if you do not need the speed of the Tesla HPWC. Much like the Tesla equipment, you’ll find two flavors of EVSEs: portable EVSEs that plug into an outlet and hardwired ones that are permanently connected to an electrical supply.

Call Your Electric Company

Call your utility for a couple of reasons:

1. Let them know you are purchasing an EV–this may prompt them to upgrade the transformer and related equipment serving your home (on their dime)
2. Most utilities have special rates for EV owners.  Its worth your while to find out what those rates are, how to get enrolled and when those rates are in effect.  It can have a significant impact on the cost of charging your car.  Generally, your utility will incent you to charge during off-peak hours and your Tesla (like most EVs) has a built-in charging timers to allow you to automatically take advantage of off-peak charging
3. They may offer rebates on your charging equipment or offer 3rd-party EVSEs at a discount

Now is also a good time to consider rooftop solar if you don’t already have it.  As with anything else, shop around.

Notes On Charging

• There is lots of debate in the owner community on what to set the daily charging level to–Tesla gives you a wide range between 50% and 90%.  If you want to be conservative,  pick a level that meets your daily driving requirements plus a safety buffer.  Personally, I have both cars set to 90% with the logic that if Tesla thought charging the car to 90% every day was an issue, they would not give you the option (if you try to charge your car to 100% too many days in a row the car pops up a warning).
• If the car detects an anomoly with the charging voltage, it will will back off the charging voltage by 25% but keep charging unless it encounters a more significant fault (in which case it will stop charging altogether, send you a notification via the app and turn the ring around the charging port a suitably serious shade of red).  Do not ignore this “backoff”–have an electrician come and check things out.
• You can schedule charging two ways in your Tesla–you can either choose a start time (i.e. start charging when your off-peak rates kick-in) or choose a departure time (i.e. be ready to go by 8am)

What if You Cannot Charge at Home

Not everyone is in a position where they can install a charger at home–typically they live in an apartment complex or condo. While this certainly makes things more difficult, this does not preclude you from owning an EV, especially if you have a short to moderate commute. There are a few options you can consider (other than moving):

• Ask the management company if they are willing to install chargers or at least outlets for charging. This used to have a low probability of success, but law and willingness are both changing, but you should expect to be asked to cover both installation and electricity costs
• Charge at work. If you have charing at work then perhaps you can charge at work during the day instead of at home at night
• Use public charging infrastructure. It’s important to be pragmatic when considering this option. It works best when you only have to do this once or twice a week–having to use use a public charger every day, just to cover your basic driving needs, will get old very quickly.

Other Questions That Come Up

• The EVSE and related installation costs might be tax deductible–depends on your particular circumstances, so check with your tax preparer.
• Make sure you get the required permits  and inspections–either set this up yourself or have your electrician include it in the cost of their quote.
• It is normal for the charging cable and handle to become warm when charging, especially at higher amperages.  The cable or handle should never to too hot to touch.  If in doubt, call your electrician or Tesla service.
• Don’t plan to use Superchargers for your daily charging–you will earn the ire of fellow owners and a nasty note from Tesla.
• Plug in your car every day – Elon says so!