100 Questions about Electric Vehicles

By David Herron

Last Update: August 18, 2019

The most convenient place to charge an electric car, but that means buying and installing a charging station. Since we don't have to install home refueling for gasoline cars, this is something new electric car owners must do. Fortunately there are a range of choices from very inexpensive (almost free) to high powered (at a cost).

Since there are many options we can only approximate the cost to buy and install a charging station at home. Your needs will dictate the end cost. There are two types of cost to consider:

Type Discussion Cost
Cost of device the EVSE (Electric Vehicle Service Equipment) - a.k.a. charging station $200 and up
Installation cost Running wiring to the service panel $200 and up
Permits Approval and inspection by city or county $100

Therefore the cost of a level 2 (240 volt) charging station for the home is about $500. The cost will increase if installation requires a long cable run, or digging a trench or other construction work, or upgrading the service panel. Another way to increase the cost is buying a fancy charging station. The cost can be decreased by using an existing power outlet.

The phrase "Level 1" simply means a 120 volt 12 amp charging station. Level 2 means any 240 volt AC charging station at up to 80 amps.

Therefore for a homeowner to install a level 2 charging station requires having a 240 volt circuit. In the vast majority of cases these are easily available. In most countries the normal voltage is already 240 volts (or so). Even in the USA where we use 120 volt devices, the voltage arriving at the house is 240 volts.

In a way buying a charging station is like buying a clothes washer or other appliance. You need to set aside an electrical circuit to power the charging station, and it requires dedicated wiring to that circuit. For most of us, we should hire an electrician to handle everything, but the more we know the better prepared we are.

Installing a charging station doesn't require anything special beyond regular electrician skills. The process is relatively straightforward, though it can get complex. The best choice is to install a dedicated wall outlet near where your car will park, then mount the charging station on the wall near that outlet. In the simplest case you have spare electrical capacity in the house and can simply run wires from the service panel. Any electrician should be able to handle installing the power outlet, and the electrical permits required should be minimal.

As we said there is a wide range of choices. Of course that will impact the cost. Elsewhere we talked about cheapest home charging, and various considerations for home charging equipment. The considerations boil down to:

In the following sections we'll go over the choices.

What is the charging rate you require? How much power (kiloWatts) does it take to run a home electric car charging station?

While we want to recharge as quickly as possible, a high charge rate is more expensive. The wiring is thicker, the power outlet is beefier, as is the charging station, all of which adds to the cost. And if the high charge rate means the service panel has to be upgraded, that adds a lot to the cost.

Therefore one should think about their real charging rate needs, and your real needs for daily driving.

An estimate of real driving needs will tell you the charging rate you require. Most of us drive 40 miles or less per day, for example. And since home base charging usually happens overnight, we have 8 or more hours to gain the needed range.

Typical range gained in overnight charging is easily calculated from this rule of thumb. (from Electric car charging speed and effective trip speed on road trips)

Charge Rate kiloWatts Range gained per hour of charging Overnight range
120 volt 12 amps 1.2 kW 4 miles range gained 32 miles
240 volt 16 amps 3 kW 12 miles range gained 100 miles
240 volt 30 amps 6 kW 25 miles range gained 200 miles
240 volt 40 amps 8 kW 29 miles range gained 300+ miles

The difference in charging time between level 1 (120 volt) and level 2 (240 volt) charging is significant.

The range gained for overnight charging considers 8 hours of charging time. Clearly even a low powered charging station adds a lot of range from overnight charging. If your budget is small it's possible to skimp a little, then for those days requiring extraordinary charging you can rely on a neighborhood fast charger. In my case I have a 120 volt charger, the University next door has 6 kiloWatt stations, and the Whole Foods a couple miles away has DC fast charging.

On the other hand if your budget is big the 6 kiloWatt or more charging system will add a lot of flexibility to your life.

The amount of power (kiloWatts) you require to charge your electric car in your home depends on what you perceive to be your needs. The table above shows you the relationship between charging power and the range gained per hour. You can decide you need the 25 miles gained/hour of charging, and therefore go for the 6 kiloWatt station at home.

The amount of energy (kiloWatt-hours) consumed will be approximately the same whether your home station is 1 kiloWatt or 8 kiloWatts. The energy required to charge your car at home depends on how far you drive, and the pattern of when you charge at home or at a public charging station. If your daily commute is 32.5 miles your recharging will consume the energy corresponding to having driven 32.5 miles. The only difference is the 1.2 kiloWatt charging station will take 8 hours to recharge that amount of energy, where the 6 kiloWatt charging station will take about 1 1/2 hours.

See: How to plan for and install 240 volt circuit to charge an electric car/vehicle?

The risk of needing a service panel upgrade

Sometimes your house will need additional wiring to support a charging station. If the electrical capacity is not enough, then the capacity must be expanded. This will mean upgrading the service panel, and in some cases upgrading the transformer at the utility pole.

As we said, a service panel upgrade is expensive. To make it clear what that means here's a few factoids:

  • The service panel is the grey box containing fuses or circuit breakers (usually circuit breakers)
  • Each circuit breaker controls one "circuit" in the house
  • Each circuit breaker handles N amps
  • The service panel has a maximum capacity - determined by the capacity of the main circuit breaker
  • The capacity currently allocated is calculated by adding up the capacity of each circuit breaker.
  • Your electrician can calculate the currently used capacity for you
  • If your electrician cannot tell you this, it's time to find a new electrician

Suppose the main circuit breaker is 120 amps.

  • If the current circuits add up to 100 amps, you can install a 20 amp circuit, which will support a 16 amp charging station.
  • If the circuits add up to 80 amps, the spare capacity supports a 40 amp circuit, which supports a 32 amp charging station (or two 16 amp stations).
  • If the circuits add up to 120 amps, then you must upgrade the service panel.

The free electric car charging station

All electric cars are sold with a portable charging station. In most cases these are low power units that are meant to plug into any power outlet and help you charge in those times you can't find any other charging.

Thing is - these are still charging stations, and many people get on just fine with even a 120 volt 1 kiloWatt charging station. You may be lucky and there is already a suitable 120 volt outlet that can be used. Just be sure the outlet is in good condition - it would not be good to accidentally cause an electrical fire by overusing a dodgy outlet.

In some cases the charging station supplied with the car supports higher power levels. In this case you'll need a matching power outlet.

Our friends who live in countries where household voltages are 240 volts have an advantage. The free charging station already runs at 240 volts, and therefore will supply a 3 kiloWatt charging rate.

The 3 kiloWatt charging station

The next cost level are the 3 kW charging stations. These are fairly inexpensive, and the cost for a suitable circuit is low.

The 240 volt 16 amp charging rate requires a 20 amps circuit.  In the USA a typical power outlet is the NEMA 6-20, or L6-20.

While charging at 3 kiloWatts is 11 miles range gained per hour of charging, an overnight charge is about 100 miles of range.

The 6 kiloWatt charging station

The 6 kiloWatt charging stations of course cost more, because all the components have to be beefier. The installation cost is also more expensive, because it requires thicker wiring, a bigger circuit breaker, and a more expensive power outlet. But the costs are not that much higher, and the convenience of faster charging is significant.

The 240 volt 32 amp charge rate requires a 40 amps circuit. In the USA a typical power outlet is the NEMA 14-50, or 6-50.

Charging at 6 kiloWatts gains about 25 miles range per hour, and an overnight charge is about 200 miles of range.

Higher powered charging stations

Most electric cars support 6 kiloWatt charging, but a few support higher power charging. You may want to maximize the home charging rate, and therefore will need a higher powered charging station.

For the ultimate you can now buy DC Fast Charging stations for home. These are pricey - $2000 or more - but of course these offer a full recharge in an hour or so. Fast charging your electric car at home

About the Author(s)

David Herron : David Herron is a writer and software engineer focusing on the wise use of technology. He is especially interested in clean energy technologies like solar power, wind power, and electric cars. David worked for nearly 30 years in Silicon Valley on software ranging from electronic mail systems, to video streaming, to the Java programming language, and has published several books on Node.js programming and electric vehicles.
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