24mph is an excruciatingly slow average speed for a 450 mile journey. No wonder they were able to be so efficient.

so, basically slower than a pro on a bicycle

nice one

Also a lot less energy efficient. They claim 171Wh per mile, that's 147 kcal per mile. On a recent 17 mile ride, I applied 591kJ (141 kcal) of work to the bicycle. So a bicycle ridden by a non-pro is almost 18x more energy-efficient than the car. (Of course more than 141 kcal of energy is required to get your muscles to do 141 kcal of work on the pedals. But not 2500 kcal worth, like the car would require. I wish a 1 hour bike ride burned 2500 calories.)

A pro, or at least someone comfortable with averaging 25mph over a long distance; given a relatively flat course, would probably require an average power output in the region of 300 watts. So even if we take the higher speed into account this works out around 12Wh/mile. ..but if we take weight into the equation; assuming the rider and his bike are on the chubby side and work out a combined 100kg - we get 0.12Wh/kilo/mile. Most of the tesla range are over 2000kg excluding passengers, so taken as a Wh/kilo/mile calculation it actually works out around slightly more than 1/3 greater efficiency at 0.086Wh/kilo/mile. Not too bad..

Of course a bicycle that is what... 1.2x human weight... is more efficient than a car that is probably ~10x human weight, when you measure it by vehicle rather than kcal per mass.

The weight of a car is not optional. If I want to move some mass between point a and point b, and I do it by car, I have no choice but to haul along that extra ~10x my weight. Measuring by kcal/mass ignores this practical reality in favour of a more precise definition of "efficiency".

Also if you're riding a bike that weights 1.2x your body weight, you have the wrong bike! Good god!

Neither 4 passengers, pile of groceries, comfortable dry seats, infotainment & air conditioning are optional on bicycle.

In other words apple to oranges comparison.

Don't know if you were kidding but I think the implication was the combined mass was 1.2x your weight. Of course even then, that's still a pretty heavy bike (I think my commuter clocks in at about 10% of my weight)

What would the pro's average speed be over the total distance? And what would an ordinary human being manage?

It is obviously the speed that makes the difference. This guy only got about 110 miles (180 km) out of a fully charged 85 kWh Tesla, driving on the German Autobahn at 160 km/h:

http://www.teslamotorsclub.com/showthread.php/32873-Discharg...

The Tesla is poorly suited for Autobahn driving because it will actually overheat and slow down if you keep driving at 120mph(200km/h) for longer periods of time, and that's not really difficult on the autobahn, especially at night.

Given those stats, his average power usage was 4.1kW, or about 5.5HP. Not bad considering that's input power including all peripherals and losses, not just power to the wheels.

This is about 20% less than the rule of thumb number for the power needed to keep a modern mid size car moving at about 100km per hour. I forget where I read it.

So yes pretty good.

And this is the principal reason why internal combustion engines are so inefficient in practice, they are used at a tiny fraction of their rated output for most of their working lives.

Of course the comparison is not quite as favourable as it at first appears because we should really measure the input power not at the output of the battery but at the input of the battery charger (equivalent to measuring the fuel pumped into a petrol engine's tank). Still impressive even if the conversion efficiency of the charger and battery combined is only 50%.

Cool, do you have a source for that rule of thumb? That's a new one for me. That's about 8HP to the wheels to keep it rolling at 100km/h right? So obviously more than that from the engine.

Re: measuring at battery input rather than output, that's a good point. Would definitely be higher that 50% charging efficiency though. I would guess at least 80% - probably > 90% if you charge it slowly enough. (Haven't done any research on Tesla chargers or batteries specifically, but I did used to be a power electronics engineer. High charging efficiency is important both for cost and, perhaps as importantly, because a slight reduction in efficiency can mean a lot of extra heat that you have to deal with.)

Alas i can't remember and a quick web search doesn't find anything I recognize. But I did find this that mentions 10hp at 50mph: http://energy.typepad.com/the-energy-blog/2010/02/energy-nee... And a few hotrodders discussing the question here: http://www.hotrodders.com/forum/how-much-hp-required-60mph-1... This on PhysicsForums: https://www.physicsforums.com/threads/power-and-tq-needed-to...

And finally a paper with real formulas and better explanations: http://wps.aw.com/wps/media/objects/877/898586/topics/topic0...

Looks like my 5kW wasn't too far off.

It required approximately 5.5 horsepower to propel the vehicle.