Charging an EV

Home Charging Costs

Written by Larry Thompson For home charging a simple formula is to multiply the battery capacity in kilowatt (kW) times the cost per kW hour.   For example:  A Tesla Model 3 Long Range model has a driving range of 310 miles and a battery capacity of approximately 75kW.  In Connecticut, using a sample residential rate of $.185, to charge a Tesla Model 3, assuming a 10% buffer is left, 75kW x $0.185 = $12.48. Learn more Connecticut has some of the highest electricity rates in the country.  A more representative average US cost is $0.10/kW to $0.12/kW. Some local municipalities have installed free public charging stations, usually of Level 2 capacity.  However most public charging stations are fee based where the fees can vary significantly. You can find the cost of each station by using the app for the charging station (e.g. www.electrifyAmerica.com) or an app that supports multiple charging stations (e.g. www.PlugShare.com) We can compare the cost of driving a BEV to an internal combustion car as follows: A 2020 Tesla Model 3 Long Range model has a range of 310 miles per charge.  Dividing the electricity cost of $10.40 by the range of 310 miles equals an electricity cost of $0.033 cents per mile. A 2020 BMW 3 Series gets approximately 26 city, 36 highway and 30 combined miles per gallon of gas.  A gallon of premium gasoline costs approximately $3.19. Therefore $3.19 / 30 mpg equals a gasoline cost of $0.11 per mile.   
Category: Charging an EV

How do I charge my EV when traveling?

Written by Larry Thompson

The short answer

There are approximately 68,000* public Level 2 and Level 3 EV charging stations in the continental US as of May 2019 with more being added each month.  These stations can be found on and just off main highways and in local and neighborhood locations and many businesses. There are a number of national providers of public charging stations and most have maps which indicate the capacity and availability of the stations.

Plugshare (www.plugshare.com) provides a comprehensive map of most charging locations in the US regardless of provider.  Other charging station manufacturers and providers can be found at:






All EV’s come with charging cables that can be plugged into standard 120 volt outlets (also known as household outlets) but charge at the rate of 3-5 miles per hour.  Although 120 volt charge rates are slow the outlets are commonly available outside homes and businesses.

Most charging stations are fee-based but some, provided by local governments are free for public use.

* www.energy.gov

Learn more

Using the EV navigation systems most EV’s are able to calculate the range required to arrive at the intended destination.  If the battery requires charging in route the EV can generally locate nearby charging stations. Using an app such as PlugShare will identify charging stations regardless of manufacture or charging provider.

Some Connecticut municipalities offer free Level 2 charging.  For example, in the Town Fairfield, there are 3 free Level 2 charging stations with a total of 5 outlets.  There are 21 free Level 2 charging stations in the Town of Westport, though parking regulations apply to those at Metro-North stations.  

The State of Connecticut provides several free charging stations at Hammonasset State Park

Category: Charging an EV

How do I charge an electric car?

Written by Larry Thompson

The short answer

Approximately 80% of electric vehicle owners charge their cars at home or at their workplace.  

For home charging, an electrician is usually required to install an electrical outlet or the manufacturer’s home charging system, including the charging cable, in the garage or on the exterior of the house. When the owner wants to charge the car they simply connect the cable to the car and the car will charge automatically.

In most cases, the electrician will install a 30 or 40 amp, 240-volt circuit. Charging times vary from car to car but a good rule of thumb is 20-25 miles of charge per hour for a 30 amp circuit.  It’s also possible to plug the car into a standard 120-volt outlet but this will generally be limited to 4-5 miles of charge per hour, less when the ambient temperature drops into the 30-degree range.  Many owners use this option when visiting friends. Fortunately, most EV’s have a phone app that allows scheduled charging during off-peak hours if you have a peak/off-peak plan.

Public charging stations also have a cable that is simply plugged into the car and the car will charge automatically.  Charging times vary widely depending on the capacity of the charging station.

Tesla’s have access to Tesla Supercharger stations generally located on or just off main highways. Charging speeds vary depending on the capacity of the particular station, how many Tesla’s are simultaneously charging and ambient and battery temperature. A good rule of thumb is to expect speeds between 150 and 360 miles of charge per hour but charging speeds decrease as the battery becomes more fully charged.

Learn more

There are several categories of EV charging stations in use today.

Level 1 Charging is provided from a standard 120 volt AC circuit sometimes referred to as a “household circuit”.  Charging times are generally between 3 and 5 miles of charge per hour.

Level 2 Charging is provided from a dedicated 30 – 40 amp, 240 volt AC circuit similar to the circuit powering a household clothes dryer.  Level 2 systems generally require an electrician to install the circuit and charging equipment in a garage or on the exterior of the house.  Charging times are generally between 20 and 25 miles of charge per hour for a 30 amp circuit

Level 3 charging is provided from public charging stations and will vary considerably in terms of charging speeds depending on the kilowatt (kW) capacity of the station. Level 3 charging equipment is commercial quality and generally not installed in residential applications and may not be compatible with all EV’s.   Level 3 charging is sometimes known as DC Fast Charging (DFC) or CHAdeMO charging but may require an adapter from the vehicle manufacturer. Additionally, there is the Combined Charging System (CCS) which provides for both AC and DC charging capability from a single plug.

Tesla recently announced and are installing Version 3 Tesla Superchargers with a capacity of 250kW per car and can, under optimal conditions, charge at the maximum rate of 1,000 miles per hour.  Tesla reports* a total of 18 Supercharger stations with 124 outlets and 7 additional stations planned.  

EV’s other than Tesla’s cannot currently use the Tesla Supercharger stations as the Supercharger will recognize only Tesla’s.

It should also be noted that charging speeds become slower as the battery becomes more fully charged.  This is especially true as the battery reached full charge. Fortunately, the rate of charge can be monitored using a phone app.

There is a plug at the end of the charging cable which connects to the car but not all plugs are compatible with all cars.  EV’s other than Tesla use a standard connector referred to as a J-Plug or SAE J1772 connector.  

Telsa charging cables have plugs that are compatible only with Tesla’s. However, Tesla supplies an adapter allowing their cars to charge at public charging stations with J-Plug connectors.  



Category: Charging an EV
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