Range Confidence: Charge Fast, Drive Far, with your Electric Car

By David Herron

Getting and installing at home electric car charging equipment

Charging an electric vehicle at home is the most convenient place to charge. You'll easily spend 10 or more hours at home, every day, so the car might as well be charging. Gasoline car owners don't have this advantage. Instead, they have to go out of their way to find a gasoline station. Electric car or motorcycle owners have the luxury of a fully charged vehicle every day.

The good news is it is incredibly easy to set this up at very little cost, depending on your need. Many people have a dedicated parking space with an electricity outlet nearby that they control.


Let's get a question out of the way -- Gasoline car owners don't have to do this, why should electric car owners have to pay to set up a charging station? Isn't it unfair that we have to shoulder the extra cost of installing a charging station just to own an electric car or motorcycle?

If you think about it, the gasoline price includes the amortized cost of gasoline stations. The pump price for gasoline is the wholesale cost plus the markup imposed by the station owner, from which s/he pays all their expenses including the cost of the gasoline station. Hence, the fact that gasoline car owners pay for their refueling equipment is obscured and buried in the gasoline cost.

Electric vehicle owners with a home charging station pay all that up front. Plus, they have the luxury of home-based refueling, having a car that is always refueled, and the fuel cost for electricity is a fraction of the gasoline fuel cost.


The lowest cost charging setup is using the charging cord supplied with the car. Every electric car is sold with such a cord. Using it with a good quality (not old and raggedy) power outlet is safe, and an inexpensive way to charge an electric car at home.

The correct name for that charging cord is "Electric Vehicle Service Equipment" or EVSE, and it is not correct to call it an extension cord. The manufacturers warn against using normal extension cords to charge an electric car. There are specialty electric car extension cords meant to be used, see: Safely use Extension Cords when charging an electric car or electric motorcycle

The lowest-cost setup also has the slowest charging rate. In the USA the 1.2 kiloWatt charging rate using the charging cord means about 10 hours to charge 40-50 miles of range. This is enough for most daily driving, but some of us will want faster charging at home. This simply requires a higher-power charging station, and a matching power outlet supplying 240 volts 50 amps capacity. The typical "dryer outlet" will do.

Electric car charging means getting, and installing, the correct equipment. They cannot just be plugged directly into a regular power outlet. The primary reason is safety, ensuring there is ground fault detection, and ensuring the vehicle cannot drive while plugged in.

Going by some terminology discussed elsewhere, the automakers do not allow Mode 1 charging cords ("slow charging from a household-type socket-outlet"). Only Mode 2, "slow charging from a household-type socket-outlet with an in-cable protection device," and Mode 3, "slow or fast charging using a specific EV socket-outlet with control and protection function installed".

Charging station plugged into power outlet

The simplest method to set up home charging is to plug a charging station into a power outlet. Your home may already have a conveniently located power outlet. If not, it's easy to have one installed. The power outlet can be reused for other purposes if desired, and the charging station can be unplugged and carried with you during trips.

The two approaches to this are:

  • Level 1: This is a regular 120 volt outlet, using the line cord charging station provided with the car.
  • Level 2: This is typically a 240 volt 50 amp outlet, using a 6 kiloWatt charging station.

All the automakers recommend against using extension cords. See Safely use Extension Cords when charging an electric car or electric motorcycle The short story is that a skinny extension cord, or flaky power outlet, increases the risk of electrical fire. If you must use an extension cord, choose one with 10 gauge wires.

It's useful to consult with an electrician. They should explain to you the maximum continuous load allowed through wiring of a given thickness, and the voltage drop over a wiring run. Electricians have the training to ensure the correct wire thickness from service panel to the power outlet. See this for some details: Electric car charging within electrical code and power outlet limits

Many Level 2 charging stations are sold with a power plug already attached. If not, it's very easy to attach a plug to the end of the wire. Your electrician would then run wiring to a power outlet with a matching socket, and then it's just a matter of plugging in the EVSE and you're good.

The actual installation is very simple:

  • Make sure the power outlet matches the plug,
  • Mount the charging station to the wall using the supplied brackets,
  • Plug the station into the power outlet,
  • Turn on the circuit breaker

Power outlet of sufficient power

An easy mistake to make is assuming that a "20 amp" outlet is safe to use at a 20 amp charging rate. The rating of 20 amps or 50 amps or whatever is not the rating for a continuous load. For continuous loads the "80% rule" applies, meaning the continuous load must be less than 80% of the rating. Electric car charging is a continuous load.

That means a 20 amp outlet supports a 16 amp charging rate, a 50 amp outlet supports a 40 amp charging rate, and so on.

In most cases charging station manufacturers recommend installing the EVSE hardwired to the electrical service panel, to improve safety. While safer, it limits your flexibility. When installed that way, a charging station is essentially fixed in place and is difficult to take with you on a trip. It's more flexible to buy a compact charging station that can be unplugged at will. Such an EVSE can be taken on trips, if needed.

That requires having a plug on the charging station power cord, and a matching power outlet.

This table shows a typical power outlets to use in the USA depending on the charging rate. For other countries please interpolate this to the power outlets you use.

Charge rate Outlet type
120 volt 12 amp NEMA 5-20
240 volt 16 amp NEMA 6-20 or L6-20
240 volt 32 amp up to 40 amp NEMA 14-50 or 6-50

When in doubt hire an electrician. Make sure the electrician understands the charging station is a continuous load. You don't want your house to burn down because the electrician didn't install the right stuff.

Charging station attached to a Junction Box

It's often recommended for the higher powered charging stations to be hard-wired to a junction box, rather than connected to a power outlet. There may be electrical reliability reasons for doing so, since power outlets can become corroded and flaky over time.

The actual installation is also fairly simple.

  • Have an electrician install wiring, in conduit if required, ending in a junction box located where the charging station is to be installed
  • Connect the charging station wiring to the junction box wiring
  • Turn on the circuit breaker

Service panel capacity

The connection between your house and the electrical grid is what's called a "Service Panel". This is the grey box housing all the circuit breakers (or fuses if your house is old enough). There's a master circuit breaker, and its rating determines the maximum power your house is allowed to draw. Try to consume more and the circuit breaker pops.

Each circuit has its own circuit breaker that will pop if you go over its limit. Each circuit breaker is rated for a capacity, typically 20 amps for an individual circuit. The master circuit breaker rating must be greater than the total ratings of all circuits in the service panel.

In other words, the service panel (and the service line leading to the house) define the maximum current capacity your house can consume. Adding a charging station may put your house over the limit. Your electrician will be able to determine this easily.

If it does send your house over the limit, you'll be facing a potentially expensive "service panel upgrade". This might entail replacing the existing panel with a new one, or perhaps adding what's called a "sub-panel".

Maybe the panel has only enough spare capacity for a 20 amp circuit to run a 240 volt 16 amp station? That is, the existing circuits might add to 80 amps, and the main circuit breaker is rated for 100. If your real needs can be satisfied with a 3 kiloWatt charging rate then go for it. Otherwise, you're facing the expense of a service panel upgrade, and perhaps an upgrade to the electrical service, and the utility company may even need to upgrade the transformer serving your neighborhood.

Electrical construction permits

Some governments require you to obtain a permit before installing a charging station. The permitting process varies from locale to locale. While it may seem overly intrusive, there are a couple valid reasons for the requirement.

Many kinds of routine electrical work require permits anyway. Electrical inspectors need to verify the work was done safely, that equipment has safety ratings (such as Underwriters Laboratory), etc. If done poorly there is a real risk of electrical fire.

Another consideration is whether the neighborhood electrical transformer has enough capacity to supply power while the car is being charged. Generally speaking the electrical grid has enough capacity to simultaneously charge millions of electric cars. But, if a group of neighbors all buy electric cars, and they're all connected through the same transformer, there's a risk they'll overwhelm the transformer.

The power company needs to sign off to avoid overtaxing the transformer. A transformer upgrade is expensive.


Go to your favorite news search engine and type in "electrical fire". You'll be greeted with story after story of homes destroyed because substandard wiring or otherwise overloaded wiring caused an electrical fire. This problem existed before electric cars. Don't let naysayers portray electric cars as dangerous because of electrical fires.

Electrical fires can, and already have, happened with electric car charging equipment. Most of the time the problem is substandard wiring. We bought our electric cars for good reasons, and the last thing we want is to be on the evening news for causing an electrical fire. Therefore it's necessary to avoid that problem by charging safely.

It comes down to ensuring the wiring is up to the job. This isn't a mystery. The electrical code was designed based on experience with electrical fires. An electric car charging station is little different from any other electrical device. The primary difference is that an EVSE running at 6 kiloWatts is a bigger load than the typical house, and it runs for quite a lot longer than usual. Perhaps that means the risk is a little higher, but any electrician worth their salt should be able to calculate the wire thickness required to handle the current.

What you should NOT do is plug into that dodgy old outlet in the garage. That's asking for trouble, so hire an electrician to replace it with a good quality outlet.

Refer to Electric car charging within electrical code and power outlet limits for an overview of electrical safety requirements.

Charging two cars at once

Once one electric vehicle gets into a household, they can easily talk themselves into getting a second or third or fourth EV. They're that addicting.

The straight-forward way to charge both cars at once is by installing two charging stations, each on its own electrical circuit. That'll mean perhaps dedicating 80 amps of your service panel capacity to electric car charging. How many houses have enough spare capacity to allow dedicating 80 amps to this purpose? In some houses, 80 amps is the entire capacity of the service panel.

An alternative is to use lower power charging stations. Two circuits for 16 amp 240 volt stations requires just 40 amps of service panel capacity. Yes your charging will take more time, but you'll avoid an expensive service panel upgrade.

In theory charging stations can be designed to share power between two or more charging cords. Unfortunately such charging stations are rare, and I don't know of one meant for home use. Instead, supporting simultaneous charging of two or more vehicles means installing multiple charging stations, and dedicating an electric circuit to each.

Sharing an electrical circuit to charge multiple cars extends the service panel capacity. Instead of two (or three or four) circuits, you only require one.

Smart (networked) charging stations versus non-networked

The current version of "modern times" says that tiny computers can (and should) be embedded into every device you see. The other day I saw a review of a completely computerized oven that's connected to the Internet, that even has a webcam allowing you to make movies of your food cooking, and all kinds of other Jetsons-like features you'd expect by going over the top with computerized integration of an oven. The cost was outrageous ($1500) but for those who seek the ultimate in technology wouldn't this be "cool"?

The fact is the capabilities of tiny-sized computation devices are growing by leaps and bounds. The same issue is playing out in every industry. What advantage can be derived by embedding an internet connected computation device in the product? For example instead of putting buttons and a display on the device, you instead provide a smart phone app that connects to the device using Bluetooth.

For electric car charging stations some useful features in a networked smart charging station include

  • Scheduling the charging time
  • Recording data about charging sessions
  • Coordinating the charging time or rate with electricity price signals
  • Remote monitoring of charging sessions
  • Notification when charging ends

V2G - Powering your house from your car

When the power goes out might it be tempting to use the electricity in your car to keep the fridge running? Some have done that and there is much research going into implementing this safely.

For now this is a matter of research, and it is still "years" before we'll see Vehicle-to-Grid (V2G) become more than just a dream. When V2G does arrive for the masses it'll do more than just handle power outages.

A big issue is that current electric car warranties prohibit using the battery for any purpose other than driving the vehicle. The reason is, perhaps, that the battery will die earlier than would be expected by the miles driven. Manufacturer warranties are based on the miles driven.

Resource guides

San Diego Gas and Electric published (energycenter.org) Electric Vehicle Charging Station Installation Best Practices: A Guide for San Diego Region Local Governments and Contractors (PDF) giving excellent advice. Importantly it names the relevant building codes and electrical codes.

National Electrical Contractors Association (NECA) NECA 413-2012, Standard for Installing and Maintaining Electric Vehicle Supply Equipment is the official guidance document for electrical contractors.

Raleigh, North Carolina, has a web page describing the process, and conveniently including a link to download the permit application form: (www.raleighnc.gov) http://www.raleighnc.gov/content/PlanDev/Articles/DevServ/Homeowner/HowToElectricVehicleCharging.html

The US Dept of Energy has a sample permit application form: (www.afdc.energy.gov) http://www.afdc.energy.gov/pdfs/EV_charging_template.pdf

Pacific Gas and Electric has several web pages discussing not only the installation process, but the advantages of electric vehicles: (www.pge.com) https://www.pge.com/en_US/residential/solar-and-vehicles/options/clean-vehicles/electric/electric.page

Range Confidence is Copyright © 2016-17 by David Herron

Getting and installing at home electric car charging equipment

(disqus.com) comments powered by Disqus