I've had a Tesla Model S for a few months now. How much does it cost me to drive it each day?
Electric vehicles are more efficient than gasoline vehicles. fueleconomy.gov says:
"Electric vehicles convert about 59%–62% of the electrical energy from the grid to power at the wheels—conventional gasoline vehicles only convert about 17%–21% of the energy stored in gasoline to power at the wheels."
Given an electric vehicles (EVs) increased efficiency, current electric rates, and gasoline prices, are you saving money on a per-mile basis when driving an EV?
Tesla provides a calculator on their website to help people estimate the cost and cost savings between electric and gasoline cars.
Tesla's calculator says it would cost $3.41 for electricity and $7.52 for gasoline for my typical daily commute of about 84 miles round trip. The text at the bottom of the calculator explains the criteria used to calculate those two costs, an electric rate of $0.12 per kWh and a gasoline car that gets 21 mpg at a gasoline cost of $2.70 a gallon. Is this a fair comparison, specifically in New England where gas and electric prices may not match the ones used in the calculator?
My previous car was a Toyota Plug-in Prius that uses unleaded gasoline. Unleaded gas is around $2.20 a gallon as of September 8th, 2016. The Prius also gets around 50 mpg for my commute, mostly highway at highway speeds.
The cost of electricity is a factor in the Tesla per-mile cost. Reading Municipal Light Department (http://www.rmld.com) rates are currently $0.16 per kWh for flat rate billing and $0.14 per kWh for off-peak with time-of-use metering. In both cases these electric rates are higher than what Tesla is using for their estimates.
The other factor is how much energy Tesla is estimating was consumed while driving. Tesla is using the EPA estimated consumption for the Model S 90D.
The EPA rating for the Model S 90D is 33 kWh / 100 miles, or 330 Wh/mile. I'm driving a version of the car with a larger rear motor, the Model S P90D which is rated at 35 kWh / 100 miles, or 350 Wh/mile. I typically get 330 Wh/mile or better on my commute in warm weather, so it looks like the EPA estimate is pretty close.
So how much energy is being used to charge and how much does it cost?
Here is a chart with a number of samples of the kWh used early each morning to charge, measured with a Neurio whole house energy monitor. The energy used to charge is what was used on the previous days commute with some additional amount for short distance local driving.
Across these six samples the average amount of energy used was 32.5 kWh. The variation between the sample is likely due to weather (colder typically increases energy consumption), driving speed, whether I've gone out to lunch or the gym during the day, or some amount of driving after work. I'm actually surprised at how consistent the results are.
NOTE: I've excluded charging from weekend driving where we typically drive either much fewer or many more miles.
My round trip commute is listed as 84 miles from Google Maps. 32.5 kWh / 84 miles is 386.86 Wh/mile. The car itself has been reporting a much lower number, maybe 320 Wh/mile on my commute to work and 280 Wh/mile on the way back. If we use the higher of the two values from the car's energy usage, 320 Wh/mile, 320 Wh/mile * 84 miles = 26880 Wh, or 26.88 kWh.
This is 82% of 32.5 kWh. The additional 5.62 kWh is due to losses in the charging systems and charging process. As an additional data point the 82% efficiency calculated here is similar to what other people have measured.
Based on the amount of energy required to recharge each day, here is the cost of driving each day with highlighting on the lowest cost options:
How would this compare to gasoline costs?
NOTE: The MPG for the Prius comes from my experience in driving a 2012 Toyota Plug-in Prius. The 'Avg car' is intended to represent the typical car on the road today and its gas mileage.
The Model S costs less per mile to drive than an average efficiency gasoline fueled car, even when considering currently low gas prices and a higher than national average $0.16 per kWh. If your electric prices are around $0.14 per kWh the Model S is more than $1.50 per day cheaper to drive.
Compared to a high efficiency car like a Prius, the Model S is slightly less cost effective. At today's gas prices the Model S costs around $0.85 extra per day.
Electric vehicles are more efficient than gasoline vehicles. fueleconomy.gov says:
"Electric vehicles convert about 59%–62% of the electrical energy from the grid to power at the wheels—conventional gasoline vehicles only convert about 17%–21% of the energy stored in gasoline to power at the wheels."
Given an electric vehicles (EVs) increased efficiency, current electric rates, and gasoline prices, are you saving money on a per-mile basis when driving an EV?
Tesla provides a calculator on their website to help people estimate the cost and cost savings between electric and gasoline cars.
Tesla's calculator says it would cost $3.41 for electricity and $7.52 for gasoline for my typical daily commute of about 84 miles round trip. The text at the bottom of the calculator explains the criteria used to calculate those two costs, an electric rate of $0.12 per kWh and a gasoline car that gets 21 mpg at a gasoline cost of $2.70 a gallon. Is this a fair comparison, specifically in New England where gas and electric prices may not match the ones used in the calculator?
My previous car was a Toyota Plug-in Prius that uses unleaded gasoline. Unleaded gas is around $2.20 a gallon as of September 8th, 2016. The Prius also gets around 50 mpg for my commute, mostly highway at highway speeds.
The cost of electricity is a factor in the Tesla per-mile cost. Reading Municipal Light Department (http://www.rmld.com) rates are currently $0.16 per kWh for flat rate billing and $0.14 per kWh for off-peak with time-of-use metering. In both cases these electric rates are higher than what Tesla is using for their estimates.
The other factor is how much energy Tesla is estimating was consumed while driving. Tesla is using the EPA estimated consumption for the Model S 90D.
The EPA rating for the Model S 90D is 33 kWh / 100 miles, or 330 Wh/mile. I'm driving a version of the car with a larger rear motor, the Model S P90D which is rated at 35 kWh / 100 miles, or 350 Wh/mile. I typically get 330 Wh/mile or better on my commute in warm weather, so it looks like the EPA estimate is pretty close.
So how much energy is being used to charge and how much does it cost?
Here is a chart with a number of samples of the kWh used early each morning to charge, measured with a Neurio whole house energy monitor. The energy used to charge is what was used on the previous days commute with some additional amount for short distance local driving.
Across these six samples the average amount of energy used was 32.5 kWh. The variation between the sample is likely due to weather (colder typically increases energy consumption), driving speed, whether I've gone out to lunch or the gym during the day, or some amount of driving after work. I'm actually surprised at how consistent the results are.
NOTE: I've excluded charging from weekend driving where we typically drive either much fewer or many more miles.
My round trip commute is listed as 84 miles from Google Maps. 32.5 kWh / 84 miles is 386.86 Wh/mile. The car itself has been reporting a much lower number, maybe 320 Wh/mile on my commute to work and 280 Wh/mile on the way back. If we use the higher of the two values from the car's energy usage, 320 Wh/mile, 320 Wh/mile * 84 miles = 26880 Wh, or 26.88 kWh.
This is 82% of 32.5 kWh. The additional 5.62 kWh is due to losses in the charging systems and charging process. As an additional data point the 82% efficiency calculated here is similar to what other people have measured.
Based on the amount of energy required to recharge each day, here is the cost of driving each day with highlighting on the lowest cost options:
| kWh to charge | $ per kWh | cost to commute |
| 32.5 kWh | $0.16 per kWh | $0.16 * 32.5 kWh = $5.20 |
| 32.5 kWh | $0.14 per kWh | $0.14 * 32.5 kWh = $4.55 |
How would this compare to gasoline costs?
| car | mpg | gallons used | $ per gal | cost to commute |
| Prius | 50 mpg | 84 mi / 50 mpg = 1.68 gal | $2.20 / gal | ($2.20 / gal) x 1.68 gal = $3.70 |
| Avg car | 30 mpg | 84 mi / 30 mpg = 2.8 gal | $2.20 / gal | ($2.20 / gal) x 2.8 gal = $6.16 |
| Prius | 50 mpg | 84 mi / 50 mpg = 1.68 gal | $3.25 / gal | ($3.25 / gal) x 1.68 gal = $5.46 |
| Avg car | 30 mpg | 84 mi / 30 mpg = 2.8 gal | $3.25 / gal | ($3.25 / gal) x 2.8 gal = $9.10 |
NOTE: The MPG for the Prius comes from my experience in driving a 2012 Toyota Plug-in Prius. The 'Avg car' is intended to represent the typical car on the road today and its gas mileage.
The Model S costs less per mile to drive than an average efficiency gasoline fueled car, even when considering currently low gas prices and a higher than national average $0.16 per kWh. If your electric prices are around $0.14 per kWh the Model S is more than $1.50 per day cheaper to drive.
Compared to a high efficiency car like a Prius, the Model S is slightly less cost effective. At today's gas prices the Model S costs around $0.85 extra per day.
Thanks for writing such a good article,Thank you. electric rates Houston
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