Today I drove the car and noticed a significant energy improvement on a regular route. I live in the hills and when I drive down to the flats, I generate some energy and when I drive back up to the house, I use quite a bit of energy. The altitude change is about 300 feet. My car’s average usage is typically about 330 Wh/mile in the local area. My lifetime Wh/mile is a bit lower than that but I’ve been across country in the Model S. The only time I experienced numbers close to 300 Wh/mile was driving on very flat freeways in mild weather.
With the new 7.0 software, rear wheel drive cars now have Torque Sleep. Tesla developed this technology for the dual drive cars. Torque Sleep is the Tesla terminology for turning off a motor when it is not needed. For the dual drive cars with a motor driving each axle, I would suspect there are many times that the car is more efficient with only one motor running. With 7.0, Tesla has now added this technology to the RWD classic cars like mine. Torque sleep on a RWD allows the only motor to go to sleep; effectively the car is in neutral but maintains control.
Today on my way down to the flats after 7 miles, my Wh/mile usage was noticeable and shockingly low – only about 183 Wh/mile. I decided to return on the exact same route. On the route home as you see on the first half of the screen I got 419 Wh/mile for the 7.1 miles to drive back home. I got an average of 301 Wh/mile on the short 14.2 mile trip.
A couple other owners have report similar improvements, although nothing in the 7.0 release notes indicates any quantitative change. But I’m more than happy to use less energy and have effectively more range on my battery.
On steep downhills, energy can be regenerated by running the motor in reverse. But Tesla must have figured out a sweet spot on a less steep grade where the car can continue at speed but can’t really regenerate energy so the software instead turns the motor off. On my route down, I am assuming there are some shallow downgrades that fit this requirement.
I will continue to watch this data for a longer period of time. Torque sleep on a RWD car may only have a limited set of road conditions to work. It would be entertaining to have an indicator on the dash that the motor is sleeping.