Gas equivalent calculation for Model Y

[jsrobe]

Trying to determine the Gas Equivalent calculation used by the Tesla app for a new Model Y.

Charge stats shows Total Charged of 180 kWh
Gas Equivalent of $88

Known Tesla assumptions:
25 mi/gal for Model Y comparable vehicle
$4.32 / gal estimated cost in PA

Gas Equivalent total miles would calculate as 509.3 mi ($88 / $4.32 * 25)

However, Model Y is rated at 28 kWh/100 miles or 3.571 mi/kWh - or 642.8 mi.

I understand the rating is based on "perfect" conditions - even assuming an acceptable range between 3.3 mi/kWh and 3.8 mi/kWh.

That would mean I'm getting 2.829 mi/kWh (509.3 mi / 180 kWh) which seems well below the stated ratings. Does this make any sense? Let me know what factors I'm missing in the calculation. I can't find anything on Tesla or any site.

 

[howardnj]

I'm not good at math but, here is what I have since Day one on September 19th 2022 to March 25th 2023
9229 miles
3556 kWh total cost thus far using both home and superchargers $863.00 Three round trips to Florida from NJ
If I divided the 9229 miles traveled by 22 MPG that was typical in my previous ICE vehicles I would have used 420 gal of gasoline priced at $3.39/gal costing $1424.00. $1424 minus $863 gives me a savings of $561 over not using gas. Miles per kWh is too complicated for me. Too many variables such as speed, wind, outside temperature, road surface, grade,etc.

 

[E90alex]

That’s not an accurate way to calculate efficiency because it’s simply the amount of energy that was fed into the car. Not accounting for conversion losses because nothing is 100% efficient and also doesn’t factor in energy consumed while the car is not driving.

Efficiency ratings are only measuring consumption for driving the vehicle.

 

[avs007]

That would mean I'm getting 2.829 mi/kWh (509.3 mi / 180 kWh) which seems well below the stated ratings. Does this make any sense? Let me know what factors I'm missing in the calculation. I can't find anything on Tesla or any site.

Lots of factors you are missing. For starters, on average how fast do you drive? When I go on road trips, while on flat ground, if I'm going 70 or less, I can average < 270 wh/mile. If I'm driving 80, I'll be averaging a little > 300 wh/mile.

If you have any inclines, that goes out the window... I live on the top of a hill. When I'm tooling around the city, I can be averaging < 250 wh/mile. As soon as I get home, it shows > 350 wh/mile. If I look at it while going up the hill, its something like 600 wh/mile... And if it's raining/wet, that can affect your efficiency as well.

 

[rjpjnk]

Trying to determine the Gas Equivalent calculation used by the Tesla app for a new Model Y.

Charge stats shows Total Charged of 180 kWh
Gas Equivalent of $88

Known Tesla assumptions:
25 mi/gal for Model Y comparable vehicle
$4.32 / gal estimated cost in PA

Gas Equivalent total miles would calculate as 509.3 mi ($88 / $4.32 * 25)

However, Model Y is rated at 28 kWh/100 miles or 3.571 mi/kWh - or 642.8 mi.

I understand the rating is based on "perfect" conditions - even assuming an acceptable range between 3.3 mi/kWh and 3.8 mi/kWh.

That would mean I'm getting 2.829 mi/kWh (509.3 mi / 180 kWh) which seems well below the stated ratings. Does this make any sense? Let me know what factors I'm missing in the calculation. I can't find anything on Tesla or any site.

If Tesla's estimator claims the charge of 180 kWh is equivalent to what $88 of gas would get you with the settings you mentioned, then it looks like they are assuming the Tesla uses about .35 kWh/mile. Not sure where the .28 rated came from.

 

[jcanoe]

The gas equivalent cost part of the efficiency analysis is:

509.3 miles / 25 miles per gallon; 20.37 gallons @ $4.32 per gallon = $88.00
$88.00 / 509.3 miles = $0.17 per mile

The electric energy calculation:

180 kWh X (enter your cost per kWh, i.e. $0.20/kWh) = $36.00 for the cost of the electricity (the kWh)
$36.00 / 509.3 = $0.07 per mile

(The 180 kWh includes all of the electrical energy consumed while charging; not all of the 180kWh made it into the battery or came of of the battery as you drove your Tesla Model Y. A reasonable estimate of charging losses would be 5%. This does not include any losses when energy is taken from the battery and used to power the drive unit(s), i.e. the motors. Overall a reasonable assumption of the charging efficiency would be 95%, so 171kWh made it into the battery and was available for driving, climate control. Regenerative braking typically can increases overall driving range, impact efficiency, by 10 to 20%.)

$0.07 / $0.17 X 100 = 41% (this is less than half of what you would have spent to drive 509 miles using gas)

By driving slower, using the Climate Control less and less preconditioning (easily done in mild temperatures) you could probably get the 41% number down to 33% of the cost of gas (at current gas prices.)

Tesla's estimated combined city/highway range estimate uses data Tesla submitted to the EPA. To equate this to real world driving (the test data is generated using multiple battery run down tests and a dynamometer to simulate city and highway driving) you would have to drive no faster than 45 miles an hour, on flat terrain with no Climate Control. The Tesla data equates to 230Wh/mi, slightly more than 4 miles per kWh (4.35 miles per kWh). Most Tesla Model Y drivers will never achieve this level of EV driving efficiency, at least not consistently.

Your efficiency, as stated is 171(kWh estimated added to the battery) / 509.3 miles for 336 Wh/mi. The average of these two values (230Wh/mi and 336Wh/mi), 283 Wh/mile, would not be an unusual efficiency result in real world driving. You can improve your efficiency, i.e. seek to drive the Wh/mi value below 300 Wh/mi most effectively by reducing your average highway speed. Driving 5 MPH slower would lower your energy consumption by 8% or 9 % (almost 10% or 27 Wh/mi.) Your efficiency would improve, be close to 300 Wh/mi. That is 3.27 miles per kWh.