Understanding Home Charging Costs

Let’s start simple and assume you charge almost entirely at home or work. There are three main things you need to know to calculate monthly charging costs: 

  1. How much you drive
  2. How efficient your EV is 
  3. How much you pay for energy 

How much do you drive?

Per the US Department of Transportation, the average American drives 13,476 miles per year, or about 1,123 miles per month. We’ll use this as the baseline for our example – but feel free to use your monthly driving figures for the next steps. Make sure to take into account any longer weekend trips or errands.

How efficient is your EV?

There are two main measures of EV efficiency: miles per kilowatt-hour (mi/kWh) and watt-hours consumed per mile driven (Wh/mi). Most car dashboards report efficiency in mi/kWh, whereas Tesla generally uses Wh/mi. For the purposes of this article, we’ll be using mi/kWh. 

Calculating EV efficiency

In most sedan and hatchback EVs, efficiency falls somewhere in the neighborhood of 3-4 miles per kWh, depending on driving habits and weather. Remember that for any vehicle, driving speed is the main thing that influences efficiency, so if you like to floor it, you will have lower efficiency than a slower driver.

Other things that impact efficiency are terrain, how much weight you have in the car, and the use of climate control. For some context, consider the extreme ends of the efficiency spectrum: some people can “hypermile” into 5+ mi/kWh territory, while the inefficient Hummer EV gets less than 2 miles per kWh.

How much do you pay for energy?

This is perhaps the largest variable – and the most nuanced to calculate, since it depends on your specific energy provider and electricity plan. There are over 3,300 electric utility providers in the United States and many regional price differences. However, the average electricity price in the US as of September 2022 is $0.167/kWh. You can check out your local or regional electricity averages on the Bureau of Labor Statistics website, or check your energy bill for what you actually pay.

Another confounding factor in electricity pricing is that each utility provider may offer different rate plans that will further determine how and when you pay for electricity. 

One type of rate plan is tiered. For example, your first 100kWh is billed at one rate, the next 300kWh at a higher rate, and then everything else at a much higher rate. This is becoming less common across the country. 

Tiered energy plan costs

As solar and EV adoption accelerates, the energy market is shifting more toward a Time Of Use rate schema, which provides for cheaper energy during low-demand hours. On the flip side, rates are significantly higher during peak hours. Time Of Use rate plans are very common among EV drivers and encourage overnight charging when demand is low and rates are the cheapest. You also don’t have to worry about overtaxing the grid with time of use charging - the cheapest electricity tends to be when demand is lowest. 

Time of use energy plans

Some utilities offer flat rate or discount plans for EV drivers, which may require a separate meter for your EV charging station.

Personally, I pay around 27 cents per kWh after all the fees and transmission charges are factored in.

The Calculation: Home Charging Costs

First, let’s figure out how much energy, in kWh, you need each month for your EV. Using our sample numbers, we divide 1,123 miles per month by an average efficiency of 3.5 miles per kilowatt-hour. This gives us 320 kWh used per month. 

Then, we just multiply that by the cost of energy. In our example, that’s $0.167/kWh, the average US rate for electricity. 

Our average US EV costs $53.44 per month to drive. As a comparison, the average gas price today is $3.74, meaning the same mileage in a 30-mpg gas car costs almost $140. 

Let’s take the same average 320 kWh a month and see what the monthly costs are for different energy rates.

Electricity cost per kWh
  • $0.10
  • $0.20
  • $0.30
  • $0.40
1123 miles at 3.5 mi/kWh
  • $32
  • $64
  • $96
  • $128
Savings over gas car example
  • $108
  • $76
  • $44
  • $12

Now, we’ll show you how to use your home energy prices to see how much a month of driving might cost you!

The basic formula for any car is:

  1. Divide monthly mileage by efficiency (in miles per kWh)
  2. Multiply the answer from step 1 by the cost of energy per kWh

Let’s go through one more example: my driving, my car, and my rate plan. Personally, I drive around 800 miles a month in a car that gets 3 miles per kWh. My electricity rate is 27 cents per kWh. 

  1. Divide 800 miles by 3 miles per kWh to get 26.67 kWh a month: 
EV efficiency calculation
  1. Multiply that by $0.27/kWh:
EV costs to drive

You can see that my monthly charging cost is around $72

Again, let’s compare my car, a Tesla Model Y Performance, to a gas car of roughly similar size, such as a Toyota Rav 4. The Toyota averages about 30 miles per gallon, so if I drove it the same 800 miles per month and paid $4.94 per gallon (my local gas rate as of early September 2022), I would be paying about $132 per month to fuel a Rav 4. This is nearly double.

And remember, I have very expensive electricity. In other places, especially those with cheaper electricity and expensive gas, charging an EV may be one-third to one-quarter the cost of driving a gas car.

EV energy prices

Understanding DC Fast Charging Costs

If you’re thinking about total EV charging, you need to consider DC Fast Charging (DCFC), which is what drivers typically use on the road. It’s super convenient, but there are many reasons to limit DC fast charging. First, due to the cost of the infrastructure and the convenience factor - it's expensive! The cost of DC Fast Charging can approach the cost of gas for comparable cars. Charging may be priced by kWh or minute. Many new EVs now come with introductory or limited free charging at DC Fast Charging chains. For instance, Ford is offering 250 kWh of free charging at Electrify America stations. 

The second reason that EV drivers don’t typically rely on DC fast charging is because it is not optimal for long term battery health. DC charging uses high voltages and produces a lot of heat - both of which can, over time, accelerate battery degradation. 

Since batteries at low state of charge recharge the fastest, you should aim to arrive at a DCFC station when your battery charge (SoC) is at its lowest. It is also recommended to stop fast charging beyond 80%. This is the point at which fast charge speeds slow down to protect the battery, and it’s usually faster and safer for your battery to “top off” at a Level 2/ AC charger.

So how much does fast charging cost?

Let’s take a car with a 80 kWh battery. If you charge from 20% to 80% SoC, you’re adding 60 percentage points of charge, or around 48kWh (0.6 x 80 kWh). A ballpark national average for DCFC charging costs is 35 cents per kWh, with potential session fees. At 35 cents per kWh and a sample $3.50 session charge, you would expect to pay $20.30 for a typical road trip stop. 

Charging from 0-100% at the same station would cost $31.50 (and would take a lot longer). Again, rates vary based on region, provider, and sometimes even surge pricing. 

Luckily, most EV drivers are able to rely on inexpensive home charging for the majority of their needs, and the money saved can go towards fast charging when needed.