For us Europeans there is always a big question when we go on road trips and have to crosse Germany. Do we have fun on the Autobahn and drive fast, but charge more? Or is it less time consuming to drive slower and charge less? This week I took it to the test and compared driving 120 kph to 150-ish kph (wanted to do 160kph, but traffic was too heavy to allow for that)

Even though driving faster is consuming more, you don't need to charge that much longer due to lower SOC with high kW rate. Of course, the equation doesn't really add up anymore when you intend to drive 200kph for a longer time. At some point, consumption becomes too high and charging times too long.

Even though driving faster is consuming more, you don't need to charge that much longer due to lower SOC with high kW rate. Of course, the equation doesn't really add up anymore when you intend to drive 200kph for a longer time. At some point, consumption becomes too high and charging times too long.

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## Comments

For example, if you are starting with 100% charge, and your first supercharger stop is the same whether you are going 120kph or 150kph, then 150kph is optimal. But if you will just reach the first supercharger at 120kph, and would have to make another supercharger stop if you were going faster, then 120kph would be optimal.

@Bighorn: it may depend on older batteries, but I get the same results for my earlier P85D and now the P100D. Maybe the software limited 60Ds might even get a bigger advantage of being able to charge longer at higher rates?

@docdac: 40kph or 25mph is the optimal speed for the lowest consumption. Tested and used that in my hypermiling record setting run :-). But that would be illegal on highways and certainly not fun for the family to travel this way. I'm talking about efficiency in total driving times, not in getting the most miles out of a single charge.

That is not entirely correct. If you could charge to 95% and avoid a big detour, that could be faster. For example driving in a 60 from Baltimore to Buffalo. Wouldn't a big charge in Harrisburg be the fastest option?

That is why I said "it depends". There are some general rules that are helpful, but no absolute rules on speed or charge level.

@finished

Ironically, it is you who are incorrect. It’s been mathematically modeled based on the taper. Your confusion arises over equating statutory miles with rates miles.

There must be a single answer.

I vote with DocDac.

45 miles per hour-- that's when the air speed begins to provide significant drag.

I remember when I was 12, that the neighbor drove from L.A. area to Alaska at 55 mph one year and then 45 mph the next year, and had better gas mileage.

I know we don't burn gas in our Teslas, but same point, I would think.

I remember 1974 when the USMC at Camp Pendleton decreed that we drive 45 mph to conserve fuel (anyone remember that?) and LtCol O.K. Steele would drive exactly 45 mph in his old Volvo and there would be a line of us behind him every morning, no one wanting to pass.

Tesla Model S and 3 have extremely low drag coefficients-- can we drive our Teslas faster and have the same efficiency as our neighbors in their Ford F 150s?

You are also conflating rated miles with the energy consumed to drive an actual mile. If you convert to watt hours, you’d see how driving very fast consumes the equivalent of 2 to 3 rated miles per mile covered. You may add an average of 200 rated miles an hour but it only gets you 66-100 miles of actual driving capacity. Efficiency peaks between 78-82 mph, after which efficiency degrades. As mentioned above, the distance between chargers will impact this, but it’s based on average distance between chargers, I’m remembering 120 miles, perhaps. If you’re going to skip a charger, the most efficient speed would drop as you’d enter the slow upper 20% of the battery to achieve that.

Different coefficients of drag, therefore, different most efficient speeds?

For Model S, I like to use this table for planning my trips between chargers and highly recommend it: http://dauger.com/tesla/supercharger.html. Just remember to convert miles to km if you drive in Europe.

As to the original question, I work as an editor at https://sportsperformancetech.com meaning I get to drive A LOT between different sports fairs and shows across the US and note down every trip details like mileage, avg speed and charge times (yeah, I am bit of a numbers person...). So based on my data, I get the most bang-for-the-charge at below 50mph , fairly in line with what others say.

I’m well aware of the OP’s intent and have been explaining this concept for 4 years now. You’re not understanding what I’ve written.

@chunky

In order to achieve rated miles at highway speed, you need to average around 20 kW. In hilly country or with headwinds it’s not difficult to see power draws of 40 to 80 kW especially when approaching triple digits. What people fail to realize is that a 200 mph charge rate does not correspond to driving 200 mph. This debate took place in earnest several years ago. Driving faster than 80 begins diminishing returns because of drag primarily. The upshot is that it’s only possible to average about 50 MPH in an 85 and 55 in a 100 over long distances. Driving 120 won’t change that.

There was a nice white paper on one of the EV sites with graphs. People are impressed with the high initial charge rates when it’s 300+ MPH, but when the kWs drop to 50 or 30 or 10 depending on how full the battery is you may only be adding 30 MPH at that point. It’s blunted by the fact the the MPH figure is a session average. Also keep in mind that you burn a rated mile in 278 Whrs but it takes 300 Whrs to replenish it. Plenty of lead footed P owners report lifetime average efficiencies over 400 Whr/m, so it isn’t too hard to imagine approaching 556 on a cannon ball run burning two rated miles for every mile covered. Maintaining that inefficiency would require one to near range charge every 120 miles which woukd take close to 90 minutes. After close to 1500 supercharger visits I guess I’d just say you’re going to have to trust me that the math matches reality.

https://teslaowner.wordpress.com/2014/12/09/driving-charging-time/