Calculating how much it costs to charge your Tesla can be much more complex than a typical gas-powered vehicle. Maybe you’ve noticed that when you charge or where you charge can change the price significantly. Many variables factor into electricity prices such as the energy cost supplied by your local utility, whether or not you use a commercial or residential charger, and the utility rate plan you’re on. Optiwatt, a free app, will automatically calculate your costs and the detailed breakdown below will demystify the complexities of determining that cost.
What elements go into the calculation?
There are five basic components that affect your charging costs:
-Battery Rating
-Electricity Costs
-Energy Rate Plan Type
-Average Distance Driven Per Day
-Charge Efficiency
After an explanation of each, we’ll run an example cost calculation.
Battery Rating
Considering your Tesla’s battery rating is important because it describes how much energy your Tesla’s battery can store. A good way to understand the concept of battery rating is by comparing it to a gas tank of a gas-powered vehicle. Just how gas-powered vehicles are designed with different fuel efficiencies, such as 30 miles per gallon, your Tesla’s battery is designed with a specific battery rating describing how much energy your battery can produce per 100 miles of travel.
Every electric vehicle battery is measured in kWh / 100 miles, also known as kilowatt-hours per 100 miles, simply measures how much energy is used by the battery to run your Tesla for 100 miles. Vehicles vary in this rating, and even different Tesla models will vary in this rating. Check out EVCompare.io’s electric car charging cost and time calculator to check the different kWh / 100 miles rating for eachTesla model. For the cost example near the end of this article, we’ll use the average kWh / 100 miles for the Tesla Model S of 28 kWh / 100 miles.
Electricity Costs
Like the varying cost of gasoline, each state will have a different average price that the electricity companies charge for electricity. These costs, measured in cents per kWh, can be found by contacting your local electric company or checking the national averages of electricity prices per state found through the US Energy Information Administration.
To calculate the charging cost, simply multiply your battery capacity in terms of kWh by the percentage of charge you want on your battery then multiply by the effective cost per kilowatt-hour in cents charged by your utility.
As a simple example let’s use the California electricity rate of 20 cents per kWh and a Tesla Model 3 with a standard 150kWh battery. If you are looking to charge the battery from 50% to 90% ( a 40% charge) at an effective rate of 20 cents per kWh, it will cost $6 to complete this charge.
For more discussion on this topic check out this discussion on the Tesla Forums.
Residential Vs. Commercial Chargers
Another important consideration is whether you charge your Tesla at home or in a commercial space via a Tesla Supercharger. Tesla Superchargers and general Tesla chargers outside your home are typically going to charge a higher rate than the rate you’ll have access to through your electricity company.
Tesla Charging Stations
It’s important to note that many Tesla charging stations charge per minute rather than per hour. In this scenario, charging costs are broken down into two categories Tier 1 and Tier 2 pricing.
Tier 1 Pricing
Tier 1 applies while cars are charging at or below 60 kW, usually when you are sharing the charging station with another Tesla. In this scenario, Tesla will charge half the typical effective rate, or 13 cents for every minute charging.
Tier 2 Pricing
Tier 2 pricing would apply to anyone who is charging above 60kW. In this scenario, the full 26 cents per minute would be applied.
Note: Per Tesla’s website, Supercharger pricing will vary depending on several factors such as on-peak and off-peak hours, the Supercharger location, and the effective charging rate for that city.
Energy Rate Plan Type
One critical difference in charging an electric vehicle versus filling up a gas-powered vehicle is how varying electricity plans can influence the overall cost of charging an EV. As we all know, gasoline companies set the price of gasoline, and you, as the consumer, can either purchase gasoline from that company or look around for an alternative.
With regards to charging your Tesla, your energy company will provide electricity to your home based on the electricity plan you’ve selected. There are four types of electricity plans you could be on: flat, tiered, time-of-us, and real-time. It’s critically important to realize that your charging costs could be drastically different, depending on which charging plan you select. In addition, the type of rate plan you have will dictate how much control you have over optimizing your charge schedule.
Flat Rate
Flat rates will allow you to charge your Tesla any time of the day and consume as much electricity as you wish at a locked-in ‘flat rate’. Your electricity company is going to provide you with an average flat rate that takes into account the associated higher charging costs for charging at peak hours and rolls that into your flat rate. In the end, this flat rate ensures dependability of your charging costs but removes the ability to optimize your cost savings.
Tiered Rates
Customers who have tiered electricity rates are charged two rates for electricity: a lower rate for the electricity used up to a certain threshold; and a second, higher rate for all additional use. If you are on tiered electricity rates and own an electric vehicle, there is a good chance the additional kWh consumed will bump you up into the next tier, causing your rates to increase.
Time-of-Use Rate
Time-of-use rates will apply a certain rate at off-peak hours and a different rate at on-peak hours. Here, you can optimize your charging costs by charging during off-peak hours. If that charging schedule doesn’t fit your lifestyle, consider another electricity rate that may better suit your needs.
Real-Time Pricing
Real-time pricing denotes electricity pricing that fluctuates throughout the day, dictated by the current market demand for energy. As demand drops and energy companies can produce more electricity than needed, prices will fall to incentivize use. This real-time pricing allows users to capture the lowest prices for charging as long as they can abide by the energy companies’ fluctuating prices.
Average Distance Driven Per Day
Car and Driver recently reported that the average miles driven per day have consistently gone up year over year, resulting in an average of 36 miles driven per day in the United States. We’ll use this average to build a model for the average cost in charging per day. Of course the more a user drives on average, the more energy that vehicle is going to consume.
Charge Efficiency
Lastly, charge efficiency is going to have an impact on the overall cost of charging your Tesla. Charge efficiency describes how efficiently your battery can accept a charge. What many Tesla owners don’t realize is that there is some energy loss when charging your Tesla’s battery. This loss is relatively low through advancements in EV charging technology, but it does have an impact. If we equate this to filling up at the pump, it would be as if every time you attempt to fill up your car with gasoline, you unintentionally spill some small percentage of gasoline out that doesn’t make it into the gas tank.
Charge efficiency comes down to a number of factors, the type of charger you are using, your Tesla Model, weather, and a number of other considerations.
Adding it Up
After addressing all of the factors that play a role in the cost to charge your Tesla, we can now build out an equation that provides a close cost estimate for both gas and electric powered vehicles - and of course, you can input your own values; as you see fit!
The Aggregated Cost Factors For Gasoline-Powered Vehicles
Cost = (Avg Miles Traveled) / (Fuel Efficiency in miles / gallon)(gasoline filling efficiency as a percentage) * (cost per gallon in dollars per gallon)
*Gasoline filling efficiency as a percentage describes the scenario of what percentage of gas makes it into the tank versus what spills out.
The Aggregated Cost Factors For Electric Vehicles
Cost = (Avg Miles Traveled) / (Battery Efficiency in kWh / 100 miles)(energy efficiency as a percentage) * (cost of electricity in dollars per kWh)
*Energy efficiency as a percentage describes the total energy efficiency of the charging process as a percentage. This can range depending on the selected charger, weather conditions, and Model.
Based on the given assumptions, we can now take all of our inputs and estimate the cost of charging. Based on a Tesla Model S with a battery rating of 28 kWh / 100 miles charging at 20 cents per kWh at 95% efficiency results in a total cost of $5.89 to drive your Tesla 100 miles.
Given that we are assuming an average daily drive of 36 miles in this example, we will simply divide $5.60 / 100 miles by 36 / 100 miles (or multiple by .36), resulting in a total cost of only $2.12 to drive your Tesla each day.
How to save the most on electricity
If you have Time-of-Use rates or Real-Time you can save money by only charging your Tesla during off-peak hours. To do this you’ll want to contact your utility company and find out what times of the day your rates are cheapest and schedule your charges accordingly. Be aware that most utilities offer completely different rate schedules depending on the time of year, or whether or not it’s a weekend.
Optiwatt is a free app that will automatically load your electricity rates and schedule your car to charge during the cheapest hours. It also takes into account annual adjustments in utility rates and will automatically update the charging schedule for winters, summers, and weekends.
Summing it all up
By considering the average cost of electricity per state, residential vs. commercial chargers electricity rates, you’ll be able to better assess the cost of charging your Tesla. Unfortunately, your home utility bill won’t break down the amount of electricity spent on your house and your Tesla. Fortunately, Optiwatt is a free app that will automatically track exactly how much you spend charging your Tesla each day.
If you are looking for a comprehensive charging guide that builds on today’s article, check out our recent article titled ‘The Comprehensive Guide to Maximizing your Tesla’s Battery Efficiency and Battery Life.’
