Home Charging Wiring Guide

Home charging wiring electric vehicles has revolutionized the market and made it much easier for people to make the switch from gas vehicles to electric models.

You can now charge your car from the comfort of your own home without having to drive to a public charging station.

Home Charging Wiring Guide

Perhaps you’re interested in knowing more about the inner workings of your electric vehicle, or maybe you’re wanting to troubleshoot the wiring that allows you to charge your car from home.

We don’t recommend working on the wiring yourself unless you are trained in the field of cars, as you could end up with lasting damage that costs a lot of money to repair.

However, if you want to know more about the inner workings of your electric car, keep on reading.

Knowing Your Charge Speed

The smallest outlet you require to charge your car will depend on a number of factors. You will need to know a few things about the vehicle and your usage of it first.

For starters, the model of your car is very important. You will also need an estimate of your daily driving mileage, along with how many hours you are able to charge your car for.

If you live in a cooler climate, you might need to take freezing temperatures into consideration.

Let’s take a 3 Medium Range Tesla as an example. It’s driven 130 miles in a day, and the charging wiring time spans from 12am to 6am. Charging time will need to be adjusted due to freezing temperatures overnight.

With this information, you can use an electric car calculator to determine the minimum output you’d need to charge your vehicle.

For the example above, the necessary charging speed would be 25.7 miles of range per hour. You’d need a 240 VAC and a maximum EV current of 32 amps.

The breaker size would need to be dual and at least 50 amps.

Using a NEMA 6-50 or 14-50 outlet as your connection to your vehicle, you could charge your car with this minimum output for 6 hours and have it in perfect condition the following morning to start your day.

Is The Minimum Outlet Required Enough?

Well, technically yes, the minimum outlet to charge your electric vehicle is enough to do the task at hand.

You will be able to charge your car by using the minimum outlet requirement. However, should you use it?

If all that’s needed is a low amount of power for one day, then charging with the minimum outlet should be okay. But the problem lies in the long term.

For example, you might find that using the minimum outlet for the maximum amount of hours overnight is working for you right now, but what about when it stops working?

If you’re charging your car for six hours a night, you might find that it still doesn’t have enough charge for you to drive it in the event of an emergency.

Say you had to drive your partner to the hospital at 2am, but your car had only been charging wiring at the minimum output for two hours. You might be in a sticky situation!

You should also take into consideration that if you were to increase your commute time and therefore shorten your charging time, you would need to use a higher outlet to make up for this loss of time and keep your vehicle at enough charge to start the new day.

For these reasons, plus a few more, we might not recommend purchasing the minimum outlet equipment and using it for an extended period of time.

So, What About A Maximum Outlet?

Reading what we’ve just explained above, you might jump straight to the idea of using a maximum outlet for the quickest charging possible.

This could be a good idea if you want peace of mind that your car is always ready in case of an emergency at 2am.

However, a lot of electric car drivers tend to take their mobile connectors with them on their commutes.

A maximum outlet mobile connector is not always suitable for storing in the car.

In fact, many high power outlets come with a warning of not to insert and remove them too many times.

If you want to keep a mobile connector in the car with you for emergencies, it would be more advisable to get a mid-range outlet instead.

This way you can keep your high power outlets plugged in at home and still have a decently powerful one for emergencies.

Using Power From Your Home

Home Charging Wiring Guide

Most homes, provided that you’re not living off the grid, have power lines running directly underneath them.

There are also powerlines running above the houses from high poles. This power comes from a substantial transformer.

From the transformer comes three wires, all working together to provide power to you and your neighborhood.

To make this easier to picture, imagine that the wires are three different colors – green, white and orange.

Between the green and the red wire, there are 240 volts. The white wire acts as a neutral wire and sits between the orange and green wires.

Between the orange and white wire, there are 120 volts. Between the white and the green wire, there are also 120 volts.

Bear in mind that the colors used for this image are just to make the description easier – in reality the wires will typically be black or white, or bare.

All of these wires pass through a meter that allows you to monitor how much power is taken into your home by your appliances.

The wires continue their journey through the meter to a service panel.

This said service panel works as the main distributor of electricity to all of the breakers in your home. The current is then sent to where it is needed – your lights, outlets, and appliances.

Let’s take a look at the different mechanisms in charge of drawing power through your home. These will enable you to get a better understanding of how your electric vehicles are charged from the grid.

Electrical Service Panel

Firstly, let’s talk a little more about the service panel in your home. As we have just mentioned, the service panel sends power to where it is needed in the home.

How much power your home draws depends on the size of it and how many outlets it holds.

Most houses draw power from between a 100 to 200 amps service. However, a smaller house might only draw from a 60 amp service. This is the same for some older houses.

Much larger houses with extremely high power drawing appliances might have service of up to 400 amps.

The utility service panel often only has one breaker that is separated from the others. The separate breaker will show a rating for the house’s service capacity – usually 200 amps for most average sized homes.

You will need sufficient open breaker spots for charging your electric vehicle. If you’re unsure of how to check for these, get the advice of an electrician. It would be safest to leave the electrics for a professional’s eyes.

If you don’t have enough space on your breaker for your electric car’s charging port, you might consider opting for an upgrade.

Otherwise, you might have to sacrifice another appliance to charge your vehicle. This might be air conditioning or solar panels.

It is worth planning for the future and considering whether you’re going to purchase another electric vehicle in a few years.

If the answer is yes, you might consider upgrading your breaker anyway so that you can fit another charging port without going through this process again.

Upgrading your service panel is relatively easy for a professional electrician, although it’s not going to be cheap. However, the benefit is that you will be getting a newer and safer breaker fitted by a professional.

To make your upgrade worth the added time and money, opt for a larger breaker with more than four additional free openings after the installation has been finalized.

This will allow you to fit more appliances in your home, or purchase additional electric cars, without having to upgrade your service panel again.

Circuit Breakers

Breakers protect the home from power surges that can be dangerous to you and your family.

If an electrical current becomes higher than the capacity that the wiring in your home can handle, the overload could cause them to heat too quickly and potentially explode. This can lead to an electrical fire.

So, as you can imagine, it is of the utmost importance that you have sufficient circuit breakers around your home.

Let’s Talk About Science

Before we can fully understand how a breaker works, we must first relearn what we were taught in school science class.

When an electrical current runs across a wire, it creates a magnetic field around it. The higher the current through said wire, the more powerful the magnetic field is around it. Are we jogging any memories?

Another important thing to remember is that as materials are heated up or cooled, their dimensions change.

For example, a wooden door will often shrink in winter and be harder to close. In summer, the wood will return to its original size and fit the frame again.

Different materials change dimensions due to temperature at different times. For example, water freezes and expands much faster than wood freezes and contracts.

Imagine that two strips of materials are bonded to one another, and we heat them both up.

However, these materials both change length due to the heat at completely different rates. One grows much faster than the other, causing the bonded strip to curve.

Remember that electrical currents flow through the metal wire, which is a conductor, and the metal gets hotter. Different metals heat up at different rates.

For example, copper heats up much slower than nickel-chrome.

Applying This Knowledge To Circuit Breakers

You might be wondering what all of this science stuff has to do with circuit breakers. Don’t worry – we’re finally about to tell you how breakers work.

Bear all of that science knowledge in mind, though, as it’s about to make sense as we work our way through this process.

The traditional circuit breaker you’d find in a house will contain two mechanisms designed to trip the circuit should a dangerous situation occur.

Firstly, there is a rod made of iron wrapped in a wire multiple times. As the current passes through this wire, the iron rod creates a magnetic field around it.

Once the current passing through the wire becomes too quick or strong, the magnet will become powerful enough to trigger the trip mechanism by pulling it towards the breaker and tripping it.

This stops the current flowing through the wire to prevent a dangerous occurrence.

The magnetism of the rod comes and goes so quickly with the current that any power surge is dealt with immediately to avoid it combusting.

The second tripping mechanism within a breaker is one that takes the current across a heating element that is made up of two paper thin materials bonded together.

The current moves through these materials and heats them up.

If the bonded materials become too hot, one material will grow in length much quicker than the other, causing the heating element to curve and hit the tripping mechanism.

This cuts all power and prevents the current from doing any damage.

The heating element trip mechanism is more suited for finding slow faults with the circuit rather than power surges.

This element takes a while to get hotter, so it allows the device to create a surge of power at startup.

Heating elements can also draw higher currents when they’re not heated, and remain this way until they get hotter.

This is why two trip mechanisms are in place so that there are two lines of defense for problems with the circuits.

When a circuit breaker experiences a short circuit, a high number of amps will be passing through the wires for a short period of time. The breaker opens and creates an arc in the middle of the contacts.

A number of copper plates are positioned to direct the arc in the opposite direction from said contacts. These plates are not connected electrically to each other.

Types Of Circuit Breakers

There are multiple types of circuit breakers out there, but your service panel requires a breaker that matches it.

So, you cannot simply use any breaker for any service panel. Again, a qualified electrician will be able to let you know what breakers your service panel needs.

Each slot on a service panel can fit a breaker that accounts for 120 volts. So, if you had a 240 volt breaker, it would fit across two slots next to one another.

There are some quad breakers on the market that take up two slots and can control one 240 volt circuit as well as two 120 volt circuits.

A quad breaker acts as an extension on your service panel. So, if you’re in need of a free slot but don’t have any on your current service panel, it might be possible to replace two of your slots with the quad breaker.

You could then replace the two slots you removed into the quad breaker, and you would be left with two free slots. One of which could be used for charging your electric car! We’re coming full circle here.

Ground Fault Circuit Interrupters

There are two wires, funnily enough, in a two-wire circuit. This is true whether the circuit is 120 volts or 240 volts. In North America, 120 volt two-wire circuits are referred to as either Hot or Neutral.

120 Volt Two-Wire Circuits

Hot is typically colored black, although it can sometimes be found as red. Neutral will always be colored white.

In a circuit, current travels across both the Hot and the Neutral wires. Along this journey, the current can get to work as and when it is needed.

However, how much electrical current there is flowing through Hot and Neutral should always equate to one another.

It is very uncommon, however, for the current to continuously be the exact same as it flows through the Hot and Neutral circuits. Current is subject to leak out as it flows through the wire.

Electricians actually often allow no more than 20 mA to be able to leak away from a circuit. If you were to touch a circuit, that 20 mA would leak out through the user’s body. That sounds dangerous, right?

Well, luckily (is that the right word?) a current larger than 50 mA can be considered potentially fatal.

This means that 20 mA is considered wide enough away from this fatal current to prevent most deaths.

240 Volt Two-Wire Circuits

In a 240 volt two-wire circuit, there are two wires – imagine that. These are called L1 and L2, or Leg 1 and Leg 2. The current flows between both legs so that the current is the same in Leg 1 as in Leg 2 at all times.

These are not color coded as commonly and can sometimes be found both black, one red, one painted red or black, or taped with colored tape. Again, these circuits are allowed to leak no more than 20 mA out.

Three-Wire Circuits

Now, in three-wire circuits, three wires can be found. These are referred to as Leg 1, Leg 2 (or L1 and L2), and Neutral.

The Neutral wire is always colored white, but the legs might be colored red and black, or they might both be black.

This is where the voltages get a little tricky. A two-wire circuit has a maximum of 240 volts achievable. However, this is not true for three-wire circuits.

A three-wire circuit can achieve 240 volts between both Leg 1 and Leg 2, or 120 volts between Leg 1 and Neutral, or 120 volts between Neutral and Leg 2.

The current between these three wires is even trickier. Here is the equation:

Current in L1 – current in L2 + current in Neutral = 0

Remember that Code allows leakage up to 20 mA, but aside from this the above equation must be adhered to.

The benefit of three-wire circuits is that you can achieve both 120 volts and 240 volts, so almost any appliance will work with it. Two-wire circuits are a little less versatile for all appliances.

For example, a clothing dryer might use 240 volts for the heating element, but only 120 volts for the light within the drum. A three-wire circuit can ensure that all parts of the appliance work together.

Ground Wires

Ground wires tend to be exposed copper or insulated with green-colored plastic with a distinct yellow stripe. This insulation is a simple safety measure to ensure that no one touches the bare wire by accident.

Ground wires will be attached to the bare metal of the appliance.

This is to protect users should something within the appliance break and leave Leg 1, Leg 2 or the Hot wire touching the metal, the current immediately is redirected from this metal into the ground.

This then trips the breaker to make the appliance safe and free of power.

If you hadn’t guessed already, if L1, L2, or the Hot wire were to touch the metal of an appliance and the user touched said appliance, the current would travel through the conductor and shock the user.

Depending on how much current was passing through, this could be fatal.

There is no current that flows through the ground wire, as it is meant to remove overflow current rather than carry it to an appliance.

Think of it more as a safety precaution over anything else to remove voltage from where it doesn’t belong.

Circling back to Ground Fault Circuit Interrupters (GFCIs), they are another safety precaution that keeps tabs on the current in all of the wires in two- or three-wire circuits.

If the GFCI detects any reduced current, it will shut everything down instantly.

It will shut the circuit down when over 20 mA of current is missing to ensure that any potential danger doesn’t have the chance to escalate.

This missing current could have leaked anywhere. If we’re feeling hopeful, we might assume that the ground wire took it and everyone is safe.

Even though the ground wire removed the danger, the GFCI still sees it as a leakage and shuts the circuit down.

However, if we were feeling a little more sinister, we might worry that the missing current could pass into your body.

As we mentioned earlier, anything over 50 mA can be considered fatal. So, the GFCI has the right idea of shutting everything down.

Currents tend to flow through anything moist or humid and then into the ground.

For this reason, GFCIs are necessary on all outlets found in bathrooms, kitchens, laundry rooms, garages, around pools, outside, and anywhere else where water is expected to be.

Having said this, you don’t always need moist conditions to experience a ground fault. In fact, a fault inside of the appliance can cause this type of fault as well.

GFCIs are always advised to add a layer of protection between you and electrical currents.

Many electrical car charging connectors contain GFCIs. This is because they are almost exclusively used outside, where weather conditions can make them wet.

Moreover, Code states that there must be a GFCI on all 120 volt outlets in a garage.


Home Charging Wiring Guide

Wire is what keeps circuits running. It will be found running from the outlet and the breaker. Depending on what conductor has been used, there will be a different safe size for the wiring.

This also differs due to the maximum current flowing and more.

Material Of Wire

Copper and aluminum are the most common metals to be used for wires. Aluminum is less expensive than copper is, but aluminum wires will need to be wider to withhold the same current as copper.

Moreover, every single attachment in the circuit needs to be certified to be used with aluminum wiring. This includes the breakers and outlets.

Unfortunately, many of these attachments are not rated for use with aluminum wiring.

Finally, you’ll need to take care in applying the right anti-oxidizing substance.

Without using this correctly, or failing to install the aluminum wiring in another way, it can become increasingly dangerous over time, possibly even causing fires or combustion through overheating.

Due to this, we would always recommend using copper wiring for electric vehicle charging. Copper wiring is easier to install and therefore reduces the likelihood of faults.

Type Of Wire

Not only is there the material to think about when it comes to wiring, but there is also the type of wire. There are many types of wire to choose from, primarily different in temperature controlling and insulating properties.

For charging an electrical vehicle, you’d ideally be looking for a wire that can handle at least 165 degrees Fahrenheit more.

The types of wire are categorized in ‘Gauges’. Here is a list of the types of wires and their ampacity.

– #3 Gauge: 100 amps

– #6 Gauge: 65 amps

– #8 Gauge: 50 amps

– #10 Gauge: 30 amps

– #12 Gauge: 20 amps

– #14 Gauge: 15 amps

Even if the Code specifies a current handling for the desired use, you can definitely use a wire with a larger handling. The smaller the number of Gauge means the thicker the wire, meaning it can handle a higher amount of ampacity.

So, a #2 is thicker than a #6. Thicker wire is often preferred, as it loses less power through resistance.

All wires lose some power when the wire heats up. However, as thicker wire does not heat up as quickly, it loses less power than a thinner wire, such as a #14 Gauge.


Conduit is the tube that surrounds electrical wiring to protect it. For smaller circuits with less power running through it, a plastic sheathing will often be used as sufficient protection. For 120 volts, 14/2 and 12/2 plastic sheathing is often used.

Plastic sheathing is better suited for thinner wires because installation can be a bit tricker on thicker wires.

A conduit needs to be certified for electrical use. Some cases have used PVC plumbing parts as a conduit, although this is not safe nor recommended in any circumstance.

Should you need more help choosing a sufficient conduit, consult a qualified electrician.

Termination Box

Any outlet must be mounted to a sufficient electrical box. The electrical box can be made out of either metal or plastic, although some outlets require a specific material.

For example, if you have used a metal conduit, you will need a metal termination box.

Metal is the preferred material for an electrical vehicle outlet due to it being much stronger than plastic.

However, some codes call for plastic if the outlet is being situated behind the wall of a room of your house.

You should also consider the size of your termination box. Code states that the box needs to be substantial enough to house all of the wiring and any outlets.

If you cannot find a metal box sufficient in size, you will need to invest in an extension box. This is a box that has an open side, so it can be attached to an original box, making it bigger.

When mounting the box outside, it will also need to be covered by a waterproof cover. This is required to meet the NECC size of box requirements.

Running a plastic sheathed wire from outside to inside is possible, but it must be installed with the correct hardware so that the box does not compromise the plastic.

The box is metal, and there are currents running within it… so make sure you attach a ground wire to the exposed metal of the tool!


There are three grades of outlet – industrial, residential, and commercial. An industrial outlet is always recommended when using a home charging port, as they are designed to withstand more usage, and the service life is much longer too.

While it might cost you more in the short term, industrial outlets will withstand a lot more than residential or commercial outlets would.

Below is a table of the sizes of outlet, as well as the voltage and circuit breakers used, as well as the industrial versions so that you can opt for this rather than a residential equivalent.

OutletVoltage (V)Circuit Breaker (A)Industrial Outlet
NEMA 5-1512015 Leviton 5262 Leviton G5262 (GFCI)
NEMA 5-2012020 Leviton 5352 Leviton G5362 (GFCI)
NEMA 6-15240 15 Leviton 5651
NEMA 6-2024020 Leviton 5461
NEMA 10-30 (not recommended)24030 Leviton 5207-S10 Leviton 5054
NEMA 14-3024030 Hubbel HBL9430A* Leviton 55054
NEMA 6-5024050 Leviton 5374-IG Leviton 5378
NEMA 14-5024050 Hubbell HBL9450A or  Leviton 55050 CE CESMPS54HR


Now that we have looked at all of the components of home charging wiring, it’s important to note a few more things before getting stuck in.

For starters, we always recommend that you don’t complete the wiring of your home charging port yourself, unless you are qualified to do so.

Instead, get a professional electrician out to take a look at your current situation and configure it for electric vehicle charging.

An electrician will have much more knowledge than you on the subject matter and will be able to wire your setup properly to avoid dangerous situations.

Another suggestion that we would give you is to get a permit from your city. This allows you to take advantage of a city inspection to ensure that the work has been completed properly and without fault.

While the permit does cost a little more money, it is worth the added peace of mind.

Be wary that an electrician might price the job up more if they know that a permit is involved, because they know that they have to complete the job correctly.

It’s best to mention the permit to the electrician, and if they start saying that you don’t need one, consider a different electrician who is going to do the work correctly without the threat of a city permit.

Spending more money on a job than you need to doesn’t sound appealing, but this is a classic case of it’s better to be safe than sorry.

Here are a number of questions to ask your electrician before having them start the job:

  • Can we use a circuit already installed instead of mounting a new one?
  • Should we upgrade our current outlet?
  • Can we use copper wiring instead of aluminum?
  • Can an additional length of wire be wrapped around the outlet box in case we want to install a wall connector at a later date?
  • Is a lightning protector worth installing?
  • Who is responsible for obtaining the city permit?
  • How much additional cost would we be looking at for using thicker wire than necessary?
  • Where should we install the outlet so that it can reach the left-rear charging port?
  • Does our home have enough power?


We hope that you have learned something valuable from our article on home charging wiring. Remember to always get a professional electrician’s opinion if you’re planning on installing an electric vehicle charging station.

This article is for informational purposes only, and shouldn’t be taken as a manual!

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