As we near first customer deliveries of Model S it is really an exciting time here inside of Tesla Motors! One of the most important and impressive performance aspects of Model S is its remarkable range and efficiency. It has a range that far exceeds every other production EV ever built, including our very own Tesla Roadster! We are, obviously, very very proud of this and therefore are excited to share with you more details here of how the Model S has come together through the final phases of efficiency tuning and optimization. We have exceeded our initial engineering targets and are positive that as a customer you will be delighted with the result.
Back in 2008, JB wrote a similar blog about the efficiency and range of our Tesla Roadster. During those times, we had recently completed tests demonstrating 244 miles of range on the Roadster. This was in accordance with the 2-cycle EPA test method that incorporated a blend of highway and city driving cycles (55% city cycle driving and 45% highway cycle driving specifically). That blog is usually recommended background reading even for a Model S customer since most of the physics and details that affect range are the same in vehicles and all electric vehicles for that matter. It also gives a description of what you as a driver can do to affect range negatively and positively relative to the EPA test procedure results. Actual cruising range will be different with options, driving conditions, driving habits and vehicle condition, as with most EPA estimates. At Tesla we take great pride in transparency with customers and feel that range is a topic where this really is particularly important. There exists not a single fixed range for any given vehicle or battery. Driving range can and will vary by a large amount depending on how you operate the vehicle and external factors such as elevation and wind change. That is the simple reality. The purpose of providing this info is so the driver/customer has a more complete picture of the things can affect his/her range and are in a better position to predict and control the result.
With the 85 kWh Model S battery we set a goal of delivering a range in excess of 300 miles using the 2-cycle EPA test procedure that we used with the Roadster. This really is a goal that no EV in history had ever achieved. We are thrilled to say we exceeded this goal.
While we have done in the past, we want to share more data plus a complete picture with you. As numerous drivers of our own Roadster (and other EVs) have seen, it is possible to get range that is different than the 2-cycle EPA procedure (both higher or lower). We have now some customers that have even driven Roadsters more than 300 miles on one charge under ideal conditions. By driving at higher speeds or with heavy utilization of cabin air conditioning or heat, other drivers might get under 200 miles.
Vehicle speed is by far the biggest variable inside the range you are able to achieve. So that you can help customers plan and predict this we will share a computer model used to simulate how far a Model S is predicted to travel under the following conditions:
Constant speed (including using cruise control)
Flat ground, no wind
Climate control OFF or using vent only (no heat or air-con)
300 lbs of vehicle load (driver plus passenger or cargo)
Windows up, sunroof closed
Tires inflated to recommended pressures
New battery pack ( The 85 kWh Model S is expected to achieve 350-250 miles of range during constant-speed highway driving at 50-70 mph with the conditions listed above. That is one quick takeaway from this graph. This is a most impressive result and represents many extensive improvements in powertrain and vehicle technology over the Tesla Roadster. We have applied years of engineering lessons and effort learned from thousands of Roadsters in dozens of countries to make these improvements. These results are more compelling than those achieved by any other EV.
You can also see that at slower speeds it could even be possible to exceed 400 miles in a Model S under the conditions above. We haven’t internally demonstrated that yet and we are planning a prize for the first customer that actually drives over 400 miles on a single charge. : )
One of the points that we feel represents a useful summary of this data is the range at a constant 55 mph under the conditions above. For the 85 kWh Model S this is slightly greater than 300 miles.
The improvements over Roadster range are clear from the comparison of curves. This is due in part to the larger battery capacity in the 85kWh Model S (versus about 55kWh in Roadster) but also due to substantial vehicle platform efficiency improvements in the Model S.
Even though the Model S is a much heavier and larger car than Roadster with ridiculously more cargo capacity the total battery energy consumption on the highway is only about 10% more than for the Roadster! This is quite amazing and results largely from the Model S having the best aerodynamics of any sedan in its class with a Cd of approximately .24. Model S aerodynamics are so optimized that the total aerodynamic drag force experienced by the car – which is significantly larger in frontal area – is almost the same as a Roadster for a given speed.
Many variables affect the actual range experienced by our drivers. Here is a summary of how a small selection of these factors affects vehicle range and their relative impacts.
Vehicle Speed
Sustained high speeds have the most dramatic effect on driving range, as the first graph above clearly shows. This is because aerodynamic resistance increases with the square of speed, requiring higher forces to push the air out of the way. In contrast slower city driving speeds are more efficient and electric vehicles have a unique benefit in stop and go, low-speed driving due to regenerative braking. Driving more slowly is the best way to stretch your range if you are ever in doubt about reaching your destination. Relative to range at a steady 55mph you can see a 50% increase or 50% decrease in range due to vehicle speed decrease or increase.
Climate Control and Outside Temperature
Climate Control energy usage is related to keeping the cabin at a comfortable temperature. Maintaining a desired temperature in the cabin requires energy draw from the battery, which affects range. It is challenging to generalize how much the use of climate control will affect your range. It depends predominantly on how different the cabin temperature is from the outside temperature, if there is a large heat load from the sun, and how long you operate the climate control system. If you are driving slowly for a very long time and operating climate control continually it will have the largest percentage impact on your range. In very hot or cold operating conditions with typical usage of climate control and driving at speeds around 55 mph you may see a 10-15% reduction in range.
New EPA Rating Procedures: 5-cycle vs. 2-cycle
When the Tesla Roadster was certified, the EPA only used a 2-cycle test that was carried out under conditions of 75 degrees Fahrenheit ambient temperature and with varying acceleration rates and driving speeds for both highway and city tests topping out at 60 mph. Recently, the EPA incorporated three additional cycles into their tests that push vehicles to greater limits. The additional cycles added as part of the new “5-cycle test” include a cold driving cycle that requires heater use, a hot weather cycle with air conditioning operation, and a high-speed cycle (reaching 80mph) with rapid accelerations.
We are very pleased to report that Model S has exceeded our initial range expectations by about 20 miles and has achieved a Roadster equivalent 2-cycle range of 320 miles and a 5-cycle range of 265 miles. This sets a new record for electric vehicle range!
Conclusion
To explain energy usage vs. driving style even more clearly, we’ve been rolling out the Go Electric Digital Experience in our Tesla Retail Stores to help customers visualize the EV energy needed to accommodate their individual driving and life style. The Go Electric Experience will be hitting teslamotors.com later this summer. We highly recommend you check it out.
The Model S sets a new benchmark as a high-performance premium sedan that is fun to drive and goes further than ever thought possible with an electric car. We are looking forward to rolling out Model S to our customers this quarter and are always interested to hear back from you about your EV experience.
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