Battery Capacity and Range Study – Model S

TLDR: I downloaded 6 months of activity and found that my 2017 Model S has less capacity and range than hoped. Still happy I have it.

A few of stats to add context around my car and habits

  • 2017 Tesla Model S 100D
  • At the time of posting, I have approx 91k miles
  • I commute 120 miles total Monday – Friday. 115 of those miles are highway
  • I cruise at roughly +8 MPH over the speed limit and use autopilot when at all possible
  • Weekend driving is usually more spirited and is approx 30 miles per day
  • 90% of the miles in this study are with the Tesla OEM 21 inch Sonic Carbon Wheels on Michelin Pilot Sport A/S 3+ Tires
  • The most recent 3500 miles are on 20 inch Sonic Carbon replicas from TSportline with Michelin Primacy A/S – 245/40/20 **I will likely do an efficiency study on the difference between the 21 and 20 inch wheels and tires this summer so I can control for temperature variance and compare the same commute at similar temps
  • I also reduced the negative camber in the rear to the minimum Tesla recommended setting after purchasing adjustable camber and toe arms

Here’s what I did

Using TeslaFi, I downloaded all of my drives and charges over the last 6 months. I then did some quick math in Excel to come up with estimated battery capacity based on driving as well as charging. I also used that data to estimate range at various speeds.

These stats are all based on my actual driving habits over the last 6 months. I would consider myself a normal driver with slight acceleration bias. Goal isn’t to go fast…just like to get to my target speed fast.

# of Drives used: 740 (deleted drives with less than 100% accuracy based on TeslaFI readings)

# of Charges used: 369 (deleted charges with less than 1kw added)

For Battery Capacity based on Driving: I divided the kW used by the % used as reported in TeslaFI

For Battery Capacity based on Charging: I the kW added by the % added as reported in TeslaFI

For Range: I took the avg watt hours/mile at various speeds and divided it by the average battery capacity calculated from the “Battery Capacity based on Driving” number

Here’s what I found

Based on driving, my battery capacity is 81.8 kW. Based on charging, it is 91.5 kW. Not sure why there is such a discrepancy. Maybe you guys have an opinion here?

I also found that my max range is achieved at 60 MPH and that range is 247.3 miles. Obviously there are several other variables not used in the calculation (elevation change, temperature, overall weather conditions, drafting other cars/trucks) but this is about as close to accurate as I can get without adding those other variables. If only I had enough time to play with it. For this study, 95% of miles used are my M-F commute.

My observations…actual range and capacity for my car is much less than the stated range and battery capacity from Tesla. The real world range of 247 miles is a pretty big difference vs the 335 miles (or 305 based on having larger wheels). Much of that capacity loss is expected over time. Especially with the mileage of the car.

All that said, love the car. Wish I’d owned one sooner. Came from a BMW X5M @ 16.7mpg…driving 35k miles per year is racking up some SERIOUS gas savings now that I have the MS.

Anyway, attached is a grid that shows my findings. Happy looking!

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