@Peter Lucas I believe you misunderstood my point. Nowhere did I say that battery degradation isn't real or doesn't exist. It is real and does exist, that is a function of battery chemistry and how the battery (car) is charged/discharged. Someone who always charges the car to 90 or 100% and is doing deep discharges (regularly running it down to below 20%) will CAUSE greater degradation to the battery than someone who keeps it in the mid-range of charge. In my case, I am a consultant and am on travel a majority of the time, which means my car sits at the airport (a lot).
When I am home and driving it, I typically drive under 50 miles a day unless taking a road trip somewhere or if I drive to a meeting a greater distance away. The result is that my "at home" mode is to normally charge the car to 60%. I drive it for the day and plug it in when I get home. My car is set to begin charging at 6am every day. That means charging is normally finished by 7 am and I have a (somewhat) warmed battery when I leave for the office (which makes a big difference in Wh per mile since the battery heater is the biggest load on the car and having the battery warmed via charging reduces heater use - especially in winter).
Now with respect to getting 70 percent of rated miles, let's be clear what we are talking about. If you are talking about the "gas gauge" display of miles on the dashboard (the one that can either show miles of range left or percent of battery charge left), that is absolutely true. This is because (as well documented) that range number is a static number based on the rated mileage battery consumption number (if memory serves, it is 293 wH/mile for a 90D model S which is what I have). Relying on that indicator or expecting it to be accurate is the same as taking the number of gallons of gas in your car and multiplying it by the EPA rated fuel economy number and expecting it to accurately predict how much range is left if your car. Cars (Teslas or ICE vehicles) only get the EPA rated fuel economy under controlled conditions or when they happen to pass through that number as the actual usage number is constantly changing. Idling at a stoplight - you are burning fuel/using energy with no miles gained so your number effectively goes to infinity. Driving in city traffic where you are constantly starting and stopping, the number skyrockets. Driving on a highway at a steady speed on a flat road (effectively no acceleration or deceleration) - the number approaches maximum fuel/energy economy and minimum wH per mile.
This is why I (and many others) have changed that display from miles (or kilometers) to "percent" (which also more closely mimics a regular car gas gauge by showing a rough estimate of how much elecricity is "left in the battery". If I want to know how far the remaining electricity will take me, I go to the energy graph on the MCU which (if set to 30 mile trailing aveage) is incredibly accurate although perhaps a touch conservative.
I do not know of a single person who has used that graph and found a different result assuming driving conditions didn't suddenly change massively (for example, you look at the graph after having driving on relatively flat terrain and then proceed to start climbing Pike's peak).
That graph is accurate because it rolls a trailing average over your last 30 miles of real world battery/energy use. Winter and the battery heater and/or car heater on? It reflects it. Raining and the wet road is causing more rolling resistance? It reflects it. Driving through hilly terrain? It reflects it. Driving in stop and go traffic with lots of acceleration and deceleration? It reflects it. Have a lead foot and constantly use lots of energy accelerating from stops? It reflects it. In short, that energy use graph and the estimated range remaining is very accurate for your car with you driving it under current conditions.
Now some will say "why does the ICE car "range remaining display" show an accurate number and the Tesla dashboard range display does not. That is simple...they use two different data sources. The Tesla uses the EPA rated number. ICE cars use an average fuel economy number to calculate it and (for American cars) also have gauges which lie about what "empty" is. People brag all the time about driving an extra 20 miles after their ICE car says remaining range is "0" or the gas gauge is on empty. European cars tend to have accurate gas gauges. American manufacturers years ago determined that people tended to run out of gas, so they padded the gauges.
Bottom line:
- Yes battery degradation is real and a function of how the battery is maintained/charged/discharged. I go easy on my battery and (according to TeslaMate) currently have a full battery projected range of 282 miles after 3 years of ownership and almost 25,000 miles driven (which puts me past the initial/steepest part of the battery degradation curve as you pointed out.
- Cars also decrease in fuel efficiency as they get older, tires wear, the engine gets less efficient. It is just harder to detect because the scale we use (miles per gallon) is so large when we are talking cars that, on average, get around 25 MPG.
- Yes, Tesla does provide a method to project how much range you have remaining in your car that is incredibly accurate - the MCU energy display set to 30 miles trailing average) and becomes even more accurate if you have a trip in the navigation system and look at the trip display which now projects forward based on actual terrain/elevation changes.
- No, the Tesla "range remaining" display on the dashboard (IC) will NOT be accurate and (in most cases) will reflect a number which is overly optimistic by up to 30% because it is based on the EPA rated range number.
- Use of "Percent Remaining" on the IC display is a better way to get a gross idea of how much electricity is in the battery.
- Teslas of all makes and models regularly are more energy efficient/get maximum range while steadily driving (minimum acceleration/deceleration) at a moderate rate of speed.
I do wish that Tesla gave us the option to display the 30 mile trailing average number as 'range remaining" on the IC. That would solve/eliminate a lot of the problems/complaints about inaccurate numbers, but to date Tesla has chosen not to do so for some reason. All that said, your assertion that Teslas do not accurately reflect the range remaining in the car is simply not true - you are just looking in the wrong place.