How does your miles/kWh change as your speed changes?

[dpilot83]

I'm considering a Model Y and I'm doing an energy cost comparison to an ICE vehicle. There are specific speeds I drive at on a weekly basis. Below are the speeds I drive and what I anticipate for efficiency at those speeds. Am I in the ballpark?

1. 22 miles of dirt roads weekly (average 40 mph)
   • 3.8 miles/kWh
   • 263 watts/mile
2. 71.5 miles of gravel roads weekly (average 60 mph)
   • 3.3 miles/kWh
   • 303 watts/mile
3. 374 miles of highway weekly (average 72 mph)
   • 3.04 miles per kWh
   • 329 watts per mile
4. 114 miles of driving in town weekly (average 30 mph)
   • 3.8 miles per kWh
   • 263 watts/mile

 

[dpilot83]

While I'm at it, what percent change is there if I'm running in 30 degree F weather?

What about 10 degrees F?

Thanks.

 

[IknowUknow]

Where are you getting these numbers from? I know for a fact that 40mph city driving peak watt/mi is around 240 w/mile. Any average driver than doesn't go balls to the wall consistently will have an avg of around 257 watt/mile lifetime.

I am using 13k miles of my own experience and with 257 watt/mile as my data*, also I don't go full throttle ever

 

[Unclepaul]

All those parameters would also effect the fuel economy of your competitive ICE vehicle as well.

Perhaps more important will be the price of gasoling and electricity in your area.

If your source of electricity is hydro, then that will make it pretty inexpensive. If you have high gasoline taxes, that will make it more expensive.

 

[dpilot83]

Where are you getting these numbers from? I know for a fact that 40mph city driving peak watt/mi is around 240 w/mile. Any average driver than doesn't go balls to the wall consistently will have an avg of around 257 watt/mile lifetime.

I am using 13k miles of my own experience and with 257 watt/mile as my data*, also I don't go full throttle ever

Thanks

I am just flat out guessing. People will say what they are getting overall but they rarely say what they’re getting at various speeds, at least that I have found.

Is there a source where this info is more readily available?

 

[dpilot83]

All those parameters would also effect the fuel economy of your competitive ICE vehicle as well.

Perhaps more important will be the price of gasoling and electricity in your area.

If your source of electricity is hydro, then that will make it pretty inexpensive. If you have high gasoline taxes, that will make it more expensive.

I’m comparing to what I would get with my current vehicle so I know the fuel economy it gets in my driving situation. Just trying to get an estimate of how a Model Y will do in the same conditions.

I can do the calculations from miles/kWh to kWh and I can adjust for charger efficiency levels and I can figure out $/mile from all of that plus my electricity rate but I can’t make a kWh estimate without miles/kWh at various speeds.

 

[EVRider-FL]

The cost of electricity and gas are not constant, so whatever you come up with isn’t going to reflect your cost over time. Don’t overthink it.

 

[ColoDriver]

You're probably in the ballpark, but are asking for incredibly precise numbers in unique situations. Your dirt roads are different than my dirt roads (which in the current badly washboard state are hard to drive at even 25mph). Your altitude is different than mine, at 9000' EVs are more efficient, whereas you might be at sea level at won't see that benefit.

But for comparison, my last car was a 2004 Volvo V70 wagon with a manual 5-speed that averaged 28mpg over the course of a year. This was a combination of city, suburban, highway and mountain driving. Driving the same roads my 2018 Model 3 Dual Motor LR averages 250Wh/mi, or about 134mpg equivalent.

Please do the testing and report back!

 

[jcanoe]

No data but I would bet that the dirt and gravel roads are really going to lower your efficiency.

Elevation changes when going uphill, head/cross winds, rain and snow will each lower your efficiency.

You did not state whether Performance Model Y, Long Range Model or the new RWD Model Y. The wheel sizes (mostly the weight of the wheels and tire combo) affect the Wh/mile by as much as 7% to 14% (depending on the speed you drive).

Expect to use 20% or more energy in winter to warm the passenger cabin, account for battery efficiency losses and overall lower efficiency in cold temperatures.

If you will be charging at home, know your all-in cost per kWh (whether peak or off-peak with a Time of Use (TOU) rate plan. In general Supercharger charging costs are 2X as expensive as charging at home.

Rent a Tesla or take one for an overnight test drive (if such a test drive is available.) Drive 30 minutes in one direction on the highway at your preferred highway speed, turn around and drive the return trip. Observe the Wh/mi for the trip as this will be an OK indicator of what you could expect (the only other major variables (unless you plan to tow with your Tesla vehicle) would be temperature, road conditions.)

Try using A Better Route Planner (ABRP). The basic version is free to use. You can plan trips and get estimates of the cost of charging while on the trip (you can compare driving at varying speeds and temperatures.) ABRP is available on the web and as a phone app. You'll find ABRP to be a helpful tool.