Cross-posting this from the Tesla Model S forum (Range Mode effect on range -- some real world numbers | Forums | Tesla Motors). Full details are available there. Here's the summary. According to Tesla, range mode saves energy in two ways: 1. Limiting climate control power 2. Optimizing the torque distribution between the two motors The second part seems to be referring to (more?) torque sleep. I wanted to isolate and measure that effect, so I did a controlled experiment. I made four separate runs on the same 32-mile loop (16 miles out and back on a relatively flat, gently sloping stretch of highway). I did two runs each on two different nights. Each night, I did one run with range mode on and one with it off. Climate control was always off. Except for entering and exiting the highway, cruise was always on and set to 70 mph. Here are the averages I got: Range mode off -- 307 Wh/mi Range mode on --- 297.5 Wh/mi Savings: 9.5 Wh/mi (3.1%) So in a D with a full charge and climate control off, range mode should be about 3% more efficient and get you an additional 8-9 miles of rated range. That's in addition to whatever savings you get from reduced climate control power. Other posters on the TM forum have anecdotally reported range mode savings of 5.5% up to 16%. If accurate, that indicates climate control may be a bigger factor than torque optimization. As always, YMMV. Unless you really need the heating/cooling power, I'd use range mode all the time for the 3%+ range increase. What's the downside?