EV Charging Basics

Electric vehicle charging is broken down into the following “levels”:

Level 1: 120V connection – plugs into wall in a standard 120V AC outlet

Level 2: 240V connection – utilizes 240V AC outlet or electrician installs in existing breaker in panel.

Level 3 (DC Fast Charge – DFCF): 480V DC direct connection to onboard charging port

This posts focuses on Level 2 charging, or the most popular for residential, workplace, and hotels. Basically, anywhere that long charging periods (ie at work or overnight) are the main charging methods for an EV. Level 2 charging is the primary type that we install at Mr. Car Charger.

Level 2 chargers can be wired directly to a circuit breaker by an electrician or they can utilize a plug to plug into an existing 240V receptacle that an electrician has installed. If utilizing a 240V receptacle there are two types of plugs:

  • NEMA 6-50P (welder plug)
  • NEMA 14-50P (stove plug)

If a 240V receptacle is not available you may need to hire an electrician to install the EV charger in an existing breaker.

The charging speed of EV’s plugged into Level 2 charging stations operating at 240V depends on:

  • The amperage of the charger (usually 16, 30, 32 or 40 amps)
  • The car’s acceptance rate in kW

The maximum power you can get from 16 amps, 30 amps, 32 amps and 40 amps chargers are the following EV power ratings at 240 V from PGE EV Fleet Guide. Keep in mind that the maximum continuous draw of the breaker is 80% of its full load amperage.

Energy (kWh) that is added to the EV battery is a function of the power rating (kW) and time plugged in (hours, h):

Energy (kWh) = Power (kW) * Time (h)

EV’s have a max power acceptance for Level 2 and DCFC. For instance, if an EV has a max charging power acceptance of 7.7 kW for Level 2 and it is plugged in for 1 hour, it will add 7.7 kWh of energy to the battery. If plugged in for 2 hours it will add 15.4 kWh of energy to the battery.

Connector Type:

SAE J1772 – Most electric cars use this connection type

Tesla SAE J1772 Charging Adapter – needed if you have a Tesla and want to use an EV Charger that has a J1772 connector

ChargeHub maintains an excellent page for EV charging station information, both for home and public charging.


Level 2 chargers will typically mount on a wall if inside of a residence (garage) or utilize a pedestal/bollard mount if at a commercial property (as shown in the image with the ChargePoint EV charger). If mounting at a commercial property, other considerations include:

  • Concrete work
  • Bollards to ensure EV’s do not hit the charging infrastructure
  • Americans with Disability Act (ADA) accessibility
  • Cord management.

An example of a Level 2 charger on a pedestal with cord management from Chargepoint is shown on the right.

Communication Capability:

Many chargers now have Wi-Fi connectivity.  Your EV may already have Wi-Fi capability and if so, you’ll need to decide if you want to use the EV’s or the charger’s Wi-Fi.  The advantage of having this is:

  • Remote Control – enabling which EV can connect to the charger
  • Data Monitoring – feedback on charging performance
  • Utility integration (if utility offers Time of Use (TOU) charging rates and other charging programs)

Other Considerations:

  • Access/Interface for commercial customers: How will they engage with the EV Charger
  • Utility incentives – ChargePoint maintains a useful database of EV charger incentives
  • Charging Cable Length
  • Outside or Inside – If outside, you’ll want to know the EV charger’s enclosure NEMA rating
  • Locking system – If installed outside using a plug (ie not hardwired)
  • Warranty – often overlooked but very important for such an important piece of equipment. Make sure the company you are purchasing from is reputable and has been in business long enough that you feel comfortable they could honor the warranty!
  • Holster to hold the cable/connector?

Below is a great graphic from Alternative Fuels Data Center on Electric Vehicles Charging Infrastructure:

How much does it cost to charge an EV

To calculate how much it costs to charge an electric vehicle (EV) you really only need to know 2 things:

  1. How big is the battery, aka how much energy it can store. Measured in kiloWatt-hours (kWh)
  2. The cost you pay your utility for electricity. Measured in Dollars/kWh ($/kWH)

This post isn’t going to go into a lot of detail into the variability in utility rates across the country but your individual utility should have plenty of information to help you find that on their website.

I’ll use my EV (2019 Audi e-tron) and my utility (Georgia Power) as an example. The 2019 e-tron has a battery capacity of 95 kWh. Despite what any information/specs says, I’ve found that we can get about 200 miles when the battery is 100% fully charged (that also makes the number nice and round for this analysis and it’s a conservative estimate).

The image below is from my October 2020 utility bill from GA Power. Utility costs typically are higher in the summer and lower in the winter so this should be a nice average. If I take my total bill amount ($133.54) and divide by total kWh used (1,123) I get a blended (which includes sales tax, nuclear construction cost recovery, etc) cost/kWh of 11.9 cents/kWh.

To calculate how much it costs to charge the car battery from 0 to 95 kWh I simply multiply 95 kWh x 11.9 cents/kWh to get $11.30. I can go 200 miles for $11.30, or a cost of $0.056 per mile.

Let’s look at a similar car from Audi to see how this compares with an internal combustion engine (ICE). The Audi Q7 is a bit bigger than the e-tron but they are close. The 2021 Audi Q7 has a gas tank size of 19.8 gallons and estimated miles-per-gallon (MPG) of 21 combined (city/highway) MPG. If we multiply 21 miles/gallon x 19.8 gallons we get a range of 415.8 miles.

It’s usually recommended to use premium fuel for cars in the luxury segment. Using the Gas Buddy app and finding the gas station near me, the premium gas is $2.19 per gallon. To fill up 19.8 gallons it would cost $43.36, or a cost of $0.104 per mile.

In other words, it costs 1.85 times more to drive the gasoline powered Audi Q7 than the electricity powered Audi e-tron! Along with being lower cost to fuel, since I have a home charging station (it plugs into the NEMA 14-50 receptacle we installed in my garage) I always leave home with a full tank of gas. On the downside, it currently takes a lot longer to fuel up if I have to charge on the road. That will be for another post!

Submetering Electric Vehicles in Apartment and Condos

We recently looked at installing EV infrastructure in a condo building parking deck and as we were leaving the resident asked us: “What about the meter?” She had been told that if she wanted to install an EV charging station she would have to have it submetered, but she was given no further guidance from the HOA. Did that mean by the local utility (Georgia Power), or with a simple digital submeter, or with a web based digital submeter, or what about a networked EV charger that also could meter energy? And once it was submetered who was going to bill for the energy consumed? I don’t think most HOAs and Apartment management companies know the answer or even how to frame the question!

As we were leaving the front desk attendant took us to look at an existing EV installation that had been done about 6 years prior. You can see from the image below that they used a simple digital sub-meter that displayed the energy consumed…but who was reading it and then billing the resident? Nobody knew anything about that installation.

The second picture shows the EV electrical infrastructure from the EV electrical panel to the assigned residents parking spot. They used a NEMA 14-15 receptacle which is great, but how do you prevent the EV charging station from being stolen?

There are several approaches to this problem and below are some of the most common we have found:

  1. Community installs Community EV charging equipment and infrastructure and EV residents pay a flat monthly fee that covers some or all of the electricity cost that the community pays for (no submetering)
  2. Community installs EV charging equipment and infrastructure that community owns at Assigned EV charging spaces. EV residents pay a flat monthly fee that covers electricity cost and EV equipment and infrastructure (no submetering)
  3. EV resident pays for EV charging equipment and infrastructure to assigned parking space. Community installs submetering equipment and billing solution to charge the EV resident for electricity they consume.
  4. EV resident pays for EV charging equipment (networked and submetered) and infrastructure to assigned parking space. Community ensures adequate space and access to electrical panels. An example of this solution can be seen here from ChargePoint with their CPF50 solution. In this option, the network solution handles all billing.

We then built the below Excel table with some of the following assumptions and additional notes:

  1. The average driver drives 7,000 miles per year (SWAG)
    1. The second image shows what the costs would be like if half the drivers were Uber/Lyft/etc drivers driving 30,000 miles per year (blended average of 18.5k miles per year)
  2. The “Miles/kWh” metric is specific to different types of EVs. More efficient EVs will have higher miles/kWh. We assumed “3”. You can find the different values from this link (and calculating using their “X kWh/100 mi” metric, which we think is kind of silly)
  3. Cost per electricity is 12 cents/kWh and there are 10 EV drivers
  4. For Option 3 and 4 (networked and/or sub-metered) adequate cell or wifi signal exists to get the data to the cloud. We threw in $500 for a wifi booster
  5. We aren’t assuming any additional electrical work needed to add additional electrical panels. If that’s needed, it would be needed across all solutions (with the exception possibly of Option 1).
  6. Monthly fees for Options 1 and 4 are based on discussions with others who have experience in the space. Monthly fees for Option 2 and 3 are arbitrarily chosen by us.
  7. Option 3 – the sub-metered option doesn’t really exist in a nice commercial package that we have found ( possibly with the exception of the option from Koben Systems where we got the image at the top of the post). It would be easy to come up with the hardware solution by using technology from a provider like Accuenergy; however, the challenge becomes how to easily bill the resident for energy consumed without a bunch of people (who cost money) doing the work.
  8. Any type of community charging should probably require some type of keyed access (physical key or card or phone) otherwise a resident or guest who hasn’t paid a fee can charge for free. Another issue with community charging is how to ensure that residents don’t hog the chargers.

Table 1: Submetering options where average driver drives 7,000 miles per year

Table 2: Submetering options where average driver drives 18,500 miles per year. IE: Half are rideshare drivers driving 30,000 miles per year and half drive 7,000 miles per year

As you can see from the above two tables, Options 1 and 2 could end up being quite costly from the Apartment/HOA viewpoint if the drivers drive a lot of miles per year or if the Monthly fee is not chosen right. Even for these scenarios, we’d recommend a simple submeter that someone in maintenance can read and keep track of to ensure the monthly fee is fair and covering most of the electricity costs. However, this wouldn’t allow any data on individual drivers (ie, to see if a rideshare driver is taking advantage of the system).

It’s a complicated topic. If you own or operate an Apartment complex or work with an HOA and would like help with your EV installation, please contact us!