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2015 model S efficiency

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I have a 2015 S85D. While it’s rated at 270 miles my mileage typically used to vary from 240-250 during ideal conditions to 180 during extreme cold weather. Yesterday I drove in 75 F weather and I kept 70mph speed for my 30 mile drive. I spent 14% of my battery usage. So that translates to 11.9 KWh and that translates to 396watt hours per mile which is really high! I definitely have done just under 300wh per mile in the past but surprised to see such high wh per mile in such good weather and driving conditions. Is it possible that my battery has degraded - is this expected?
 
I spent 14% of my battery usage. So that translates to 11.9 KWh and that translates to 396watt hours per mile which is really high! I definitely have done just under 300wh per mile in the past but surprised to see such high wh per mile in such good weather and driving conditions. Is it possible that my battery has degraded - is this expected?

A couple comments.

First, a degraded battery in my experience will not impact your actual Wh/mi energy usage. That's really a measure the rate you are using energy. A degraded battery capacity gets into have less energy available, so using it at the same rate takes you shorter distance.

My other point is that I think you've off base with how you judged the 396 Wh/mi efficiency rate. Your statement of 14% of your battery usage translates to 11.9 kWh of energy use is off as the usable capacity of a 85 battery pack, even brand new, was not 85 kWh. You can find various numbers out there as to what people have best reversed engineered it to be, but it was never 85 kWh usable. The easiest way to tell what your actual energy use is to go by the trip meter for a continuous drive.

As others already said, wide range of factors that will influence your actual energy use on a drive by drive basis and averaging over a period of time time helps.. Also factors like whether you have 21 inch or 19 inch wheels and the type of tires also impact what your wH/mi number will be, so tough for me to tell you what your would need to get 1 mile actual range for 1 rated mile, but it's likely in the mid 280s if you have 19 wheels. If you have 21s, then will be higher, likely closer to 300.
 
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Excellent points. Also remember that when you first start to drive the Tesla the battery has to be cooled or warmed to the temperature they like. There are other "startup costs" in battery usage. Thus a short trip takes a lot more power per mile than a longer trip.

At one time it was determined that Tesla was including any power used by the vehicle while sitting in it's watt hours per mile usage calculation. This would also make short trip figures seem unreasonably high. Assuming they still do that.
 
At one time it was determined that Tesla was including any power used by the vehicle while sitting in it's watt hours per mile usage calculation. This would also make short trip figures seem unreasonably high. Assuming they still do that.

Energy use while the vehicle is sitting is only included in the Wh/mi usage calculation once you have entered the vehicle. This would be the case you start driving, get stopped at something like a railroad crossing or traffic jam and not moving for say several minutes.

If will not include any energy consumption while the vehicle is "off" such as you activate the HVAC via the app to precondition the car.

My car sits parked for several weeks at a time. The trip meters remain unchanged although the parasitic loss on my car tends to average at about 2% every 3 days.
 
Thanks for the replies. I do have the 19s and was expecting under 300wh per mile. Yes makes sense that 85kwh is high a number to use in calculations. In fact was wondering about it, so is it the case the usable power was May be lower than 85kwh even when new but does that go down as the battery ages?
Will watch for next few days and will get an average and compare it with what the car reports. Today the car reported 300wh per mile as average for the last 30 miles.
 
Thanks for the replies. I do have the 19s and was expecting under 300wh per mile. Yes makes sense that 85kwh is high a number to use in calculations. In fact was wondering about it, so is it the case the usable power was May be lower than 85kwh even when new but does that go down as the battery ages?
Will watch for next few days and will get an average and compare it with what the car reports. Today the car reported 300wh per mile as average for the last 30 miles.
You need to remember a couple things.

The report Wh/mi number that's averaged over the past 30 miles is only while the car is being driven. Same for the Wh/mi number that is being reported in the Trips tab for the Trip A, Trip B values.

Any energy consumed while the car is parked and not being driven is not considered in either of those calculations, but directly comes from the main battery. This includes any energy that gets consumed by preconditioning, using cabin overheat protection, etc. Depending upon you use case, that can be very minor, or it can be very significant.

That's where trying to do any form of calculation looking at the total number of RM use, or percent battery consumed over time is only really valid if you're doing a continuous drive and not a variety of short trips and aggregrating them.

I have a mid-2016 MS90D with 19" rims. My understanding is the range and overall efficiency on the refreshed front end that I have is potentially a little better than your 2015 MS90D. From tracking data over the past 6 years on my car, I need to average around 274 Wh/mi while driving to achieve 1:1 between the indicate rated miles consumed and the actual miles traveled. That's where for your car you need to be somethere in the mid-to-upper 280's to reach that 1:1 parity point.

Honestly, the best way I've found to judge change in battery capacity over time is to simply charge the car to a set percent, say 80% or 90%, and then just track the displayed range in rated miles at the end of charging. You can ratio that to 100% and use this versus the stated range number for a relative change over time. That's an indication of the change in the available or usable energy capacity of the pack, not an indication that the efficiency (or Wh/mi) changes.