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Tesla Reveals High-Profile Electric Roadster; Calculates EV is More Than 3x as Efficient (WTW) as Fuel Cell Vehicle

The Tesla Roadster.

Tesla Motors unveiled its much-anticipated all-electric two-seater roadster. The lithium-ion battery powered sportscar features a 248hp (185 kW) electric motor that accelerates the car from 0 to 60 in four seconds.

Built by Lotus for Tesla, the Roadster has a range of about 250 miles and a top speed of 130 mph. The price for the Roadster will be around $100,000.

The custom-designed battery system (Energy Storage System) weighs in at close to 1,000 pounds and uses commodity lithium-ion cells. The system addresses thermal balancing with a liquid cooling circuit.

The 3-phase, four-pole motor uses a low resistance “squirrel cage” with large copper end rings. This allows the rotor to develop high current flows and torque, with low resistance losses. The use of a small air gap allows tight inductive coupling which, combined with low loss magnetic materials, enables the development of high torque at high rpm. Together, these factors allow the induction of large currents, even at high rpm, producing much flatter power and efficiency curves from approximately 2,000 rpm to 12,000 rpm. The motor redlines at 13,500 rpm.

(Devising a cost-effective method for the production of copper motor rotors has been under investigation for years. Siemens introduced three motors with die-cast copper rotors to the US market in April.)

Comparing Well-to-Wheel Efficiency and GHG emissions. Click to enlarge.

In a white paper (The 21st Century Electric Car) published on the Tesla Motors website, the company calculates the tank-to-wheel (actually, the “electrical outlet to wheel”) energy efficiency of the Roadster to be 2.18 km/MJ.

Assuming electricity supplied from a combined-cycle natural-gas-fired generator, and accounting for transmissions losses over the grid leads them to calculate the “well-to-wheel” efficiency of the Roadster to be 1.14 km/MJ—double the efficiency of the Toyota Prius.

Tesla then tackles the question of hydrogen fuel-cell vehicles (FCV) fuel cars, deriving a theoretical efficiency for an FCV fueled with hydrogen produced by steam methane reforming of 0.85 km/MJ.

Theoretical efficiency of battery-electric and fuel-cell vehicles. Click to enlarge.

This is impressive when compared to a gasoline car, though it is 32% worse than our electric car. But real fuel-cell cars do not perform nearly this well.

...The best fuel-cell demonstration car measured by the EPA is the Honda FCX, which gets about 49 miles per kilogram of hydrogen, equal to 80.5 kilometers per kilogram. We know that the energy content of hydrogen is 141.9 MJ/kg, so we can calculate the vehicle efficiency to be 80.5 km/kg / 141.9 MJ/kg = 0.57 km/MJ.

...When we calculate the well-to-wheel energy efficiency of this Honda experimental car, we get 0.57 km/MJ x 61% = 0.35 km/MJ, not even as good as the ordinary diesel Volkswagen Jetta, let alone the gasoline-powered Honda Civic VX or the Honda Insight hybrid car.

However, some proponents of hydrogen fuel cells argue that it would be better to produce hydrogen through electrolysis of water. The well-to-tank efficiency of hydrogen made through electrolysis is only about 22%, and the well-to-wheel energy efficiency of our theoretical fuel-cell car would be 2.78 km/MJ x 50% x 22% = 0.30 km/MJ, and the well-to-wheel energy efficiency of the Honda FCX would be 0.57 km/MJ x 22% = 0.12 km/MJ, even less efficient than a Porsche Turbo.



about lithium

They'd have to use something other than lithium batteries before I'd even consider it. Have you not seen the reports of lithium batteries exploding? Everyhing from flashlights to laptops. Not to mention the incident on the UPS plane with them.

1 little CR123 battery packs a hell of a punch and if you breath the fumes, you can be screwed too. There's video on the net of people overcharging on purpose to show the effects and it's not something to sneeze at.

Besides, I'm not convinced the REAL Tesla even needed to use batteries. ;)

Sunny Tai

Note: "overcharging on purpose"


Wouldn't you'd think there are electronic safeguards to stop that happenning in a $100,000 car? But, oh wait, there are always idiots who'd try and blow things up on purpose.

And you think they would sell this car if they're not confident that their car is safe?



are you on drugs?, before you claim that you know of a car that never needs recharging maybe you should learn to spell!

Joel Oliva, idiot of the future!


There is a lot of useful information in these comments...three points that haven't received much attention...

1. Current EV batteries are lasting longer than expected. For example, some organization has 5 RAV4s with 100k miles on them. The batteries have lost little capacity. They are now expecting 140k miles out of them. Remember that batteries don't die...they are murdered.

2. Maintenence is much less with EVs. I don't have this quantified, but electric motors are very reliable, as you know. They are expected to last longer than ICE cars.

3. There are various incentives for EVs which reduce the costs a few thousand $ at least.


Bullocks (thats getting to be a popular expression) to the nah sayers. They just want to burn fosil fuels cause it feels good.
First the myth..

Most people dont drive 250 miles a day.
Most folks drive 250 miles a week.
Some drive more but not a lot more.

Even with urban sprawl my daily if I drove would be
550 miles a week and I am far from the center of the city.

So for the average 80 charges a year (allowing for some extra traveling during a normal year) how long would these batteries last? 2000/80 25 years.
I have never owned a car for 25 years.

Lets just say your drive 500 miles a week.
Thats 26K per year, which is quite a bit. You would recharge about 3 times a week. 750 miles a week.

That gives you a over 12 years of battery life.
So whats the problems with batteries again.

Can anyone start a car company?
How can LiIon battereis be made cheaper?
Thats my question. Since they are used in Laptops
they are already mass produced. The new nano tech battereis are even used in the drills now by DeWalt.
Is the mark up that high on the batterey production?
Is it a 100% over cost kind of markup?
Folks it looks like a car maker should BUY a battery maker and make an EV doesnt it?

I would love to take that GM Hydrogen rollerskate and place LiIon batteries in it with a durable lightweight
Saturn space frame exterior. That makes sense to me.
Anyone have money to start a car company like that?
One more additoin I would love to experiment with.
Most of the energy to make a car move is expended during take off. Is there any way to combine a compressed air assist with the electric power? That way the electric power could be used to maintain and accelerate after the car is put into motion. Just ideas,,



"So for the average 80 charges a year (allowing for some extra traveling during a normal year) how long would these batteries last? 2000/80 25 years.
I have never owned a car for 25 years. "

One point of note about the cycles is that those figures should [i]improve[/i] if the drivers faithfully "top up" the batteries every night, rather than running until the battery is low, and refilling it. The deeper you cycle the batteries, the more rapidly they will wear out. By only cycling them a fraction of their capacity though, they should last MUCH longer than the rated number of deep cycles times the max range.

This principle, along with several other things, is why "overengineering" an elecrtic vehicle is such a great idea. By having such a large battery pack, it means that most poeple's average drive won't cycle the battery pack deep enough to promote accelerated wear. Likewise, even as the battery pack gradually loses capacity (both in peak power, and range) over the years, the fact that it is designed with power and range to spare will mean that the vehicle would still deliver satisfactory performance, and be perfectly useful, even with a sub-par battery pack.

The same thing goes with using a high-horsepower elecrtic motor. There are no pumping losses associated with a high-displacement gasoline engine, so there is almost no efficiency penalty at all for adding in extra peak power. What this means though is they can market a vehicle to be competetive price-wise with high-end sports cars. Making the vehicle have less performance competetive with a $14000 econobox however would be difficult, as the LiION batteries likely cost more than that by themselves. Once you have the batteries however, making the car into zippy sports is not very difficult.

One solution that might be interesting would be a series hybrid built on the same platform. Instead of the costly battery pack, they could throw in a small dedicated generator designed to run smoothly at a fixed RPM, and say a 40 mile range battery -- once depleted halfway, the motor would then come on and trickle-charge the batteries.

anti gravity

if the battery pack lasts you 4 years or more i bet a new pack will cost a lot less than the present one in the car, plus it will prob be lighter and hold more charge so infact in 4 years your car is better than new, faster more range ect
and dont worry about the electric motor it will run forever, good for millions of miles easy
this is why GM ect dont want electric cars they make far too much from ICE


Dear passionate EV experts...

This is a very long topic and I may have missed it if someone has already said this, but...

On the issue of battery range:

Consider my cell phone. Each charge is only good for a few days, but I hardly ever notice that because it charges automatically each night when I place it in its recharge-holster. So we would have a similar setup for our electric vehicles, which charge automatically when we park them in our garage or at work.

This is the difference between charging automatically versus stopping at a gas station (or "electric station") for fill-ups (or recharges). If I can recharge automatically at home and at work, it's a whole new experience. More like never going to the gas station and always being charged.

So a 100 mile range is fine for most days. The car is always charged in the morning. I almost never need to stop at a charging station.

Yes, if I'm on the rare road trip, mileage becomes an issue, but I usually rent a car anyway to avoid mileage and road-wear on my own car.

Yes, if someone has a high-mileage job, a different vehicle or charging strategy would be necessary.

Overall, though, I think the perception of battery-range is incorrect, as it would apply to real daily use. If I were selling an electric vehicle with less range than a gasoline vehicle, I would create a commercial which parallels the use of an automatic cell-phone charger with an automatic electric vehicle charger in daily use.

Offer me an electric car at a comparable price to the average sedan with a range of 100 miles per charge, which charges automatically in my garage, which can go freeway speeds, and I will buy it.

john galt

The RUB... EVs offer so many more advantages than ICE cars, but many opine that the EV must provide all the capabilities of the ICE car + all of the advantages of an EV for the same price. RIDICULOUS, but not impossible.

Technology, especially in electronics, has a history of incredible advances in a short period of time. 6 years ago a Sony 5 disc carousel DVD player cost about $600. These now can be had from a range of producers, with the low end priced at $75. Performance of laptop computers is another example. In 6 years the processing speed, memory capacity, hard disc size, and drive capability (CD/DVD/RW) has increased exponentially, while the price has actually gone down by over 200 percent.

This type of innovation being passed along to the consumer has never happened in the ICE car industry. So, I would say the ICE club is crapping their pants in fear of when the EV industry takes off in earnest. The competitive innovation of the electronics and computing industry could bury the monolithic auto/oil/parts cartel that has bullied this country for the last 100 years.

It is amazing that people don't realize that EVs can essentially be fueled by almost "anything" wind, water, solar, geothermal, waste gas, etc. The electricity transport grid is already in place..basically a freebie not unlike the internet, where all the development and basic infrastructure was already put in place by DARPA and universities.

Range, fill ups at gas stations, etc., are myopic customs of an incipid ICE culture. Once we can see beyond that paradigm, EVs can provide all the personal transport capabilities anyone should realistically need.


If you want to stop all the crap on engine then coming soon by a company is the all new auto recharge electric car, reaching speeds of 250 MPH and 300 HP, and heres what is going to confuse you.... you never stop and recharge, it is not solar, nuclear, gasolone, no PURE ELECTRICTY and coming soon Joel will come on the national news and address the biggest relief in the history in the world because not only can he make Cars, in production is the New Airplanes of the future because they are pure electricity and rehcarges internally like the vehicle. now back to the vehicle, you basically in simple terms, start the car and begin and never stop until you want to, not because your running out of gasoline. Coming soon, This is no joke, just wanted to let you know, And heres the best part of all. He is not interested in making big Profits like all these greedy pricks, no hes going to sell the vehicles starting at $9,000, yes in american dollars. Finally the Americans have a made the best reliable vehicle with only once a year maintenance. better than any comapny in the world because it never needs anything, and everything has a backup, event even the lightbuld, they automatically, this is not a dream this is a reality and YOU deserve it, Email me at and address the Title as A.R.E.C and your name, thanks again for your time, and this is on the way, so now where are the industries going to take your money this time, think about that but welcome to the properous year of 2006 and 2007. Inventor and future Leader: Joel


"It is amazing that people don't realize that EVs can essentially be fueled by almost "anything" wind, water, solar, geothermal, waste gas, etc. The electricity transport grid is already in place.."
Sorry but that is just pure ignorance talking. The grid in place is currently strained to the limit and a complete new additional grid would be required if everyone suddenly went completely stupid and started paying $60K for an econobox EV that costs four times as much each year in batteries as would be required for gasoline. That's not even considering the changes
required for the new service stations. And, best of all, these moron EV drivers will be inconvenienced up the kazoo. I really don't envision lack of supply of EVs being a big issue ...


Hi - I'm new to this forum (which is great by the way) - so apologies if this is a no-brainer...

I've seen stated in much of the media around electric vehicles that charging overnight will not be a problem since "electric companies have excess capacity". Has anyone done the math on what happens if, say, 10 million households are charging overnight.

I think I saw stats on the Tesla car stating that you need a 240V/70A circuit and the charge would take 3-4 hours, which by my math means 17kW of power drain, and 50kWh+ over the charge cycle. Multiply that to 10 million users is a power usage of 170 Gigawatts or 500 Gigawatt hours of charging. For comparison, the total US installed generating capacity is around 1000 Gigwatts. This assumes no problems of distribution/transmission.

I'm not an electrical engineer so would welcome any corrections to these assumptions, but seems like we have a lot of work to do on the supply side too.... D


The first 100 vehicles have been sold & the company is taking orders for the next 100. Sounds like quite a successful beginning. There are deep pockets behind this venture & it WILL be quite the success story in time.

There is an article in the August 2006 issue of Wired magazine on page 163.

The mind boggles somewhat at the blind ignorance here in the comments. However that is made up for by the earnest thirst for change and knowledge among others. Change ain`t easy but it is mandatory for our survival.

The Tesla is a reasonable beginning I think.

“Once you start a project, amazing people start to join” - Major Nate Allen (U.S. Army)


David, the 17 KW for 3.5 hours is for a full recharge, for 250 miles of driving. The average miles per day is about 30-35.

You'd need to increase the grid's average output by very roughly 60 GW (210M vehicles, 12k miles/year, 200 whrs/mile) or about 15%, to power all 210M light vehicles in the US, if they were electric.

Electrics only use about 1/8 the power of gas ICE's.


While I may drool over this little sports car, I really hope they are successful enough to get into other designs, not just a cheaper version of this, but also something more aero, with a couple more seats and a roof (they should do it on a different production line - those Bentley Bangin' Brits are too pricey!)


Im not sure how you get those GHG emissions. 2.18 km/MJ corresponds to 0.205 kWh/mi. Very good for an EV. Take the very optimistic CA mix at 280 g/kWh x 0.127 kWh/km = 36 g/mi. Still not too bad. A more realistic CO2 factor is 400 g/kWh (see California Hydrogen Highway Blueprint Plan, Societal Benefits Report); however, if you own your own solar power, you could drive your CO2 factor lower.

john galt

>>"It is amazing that people don't realize that EVs can essentially be fueled by almost "anything" wind, water, solar, geothermal, waste gas, etc. The electricity transport grid is already in place.."<<

"Sorry but that is just pure ignorance talking. The grid in place is currently strained to the limit and..."

It seems Kent has added his own personal contribution of ignorance. Review the follow up posts and it is convincing that minor enhancements to the US power distribution grid can very likely support EV needs, smartly managing recharge cycles through off peak charging, etc. Ignorance responding to ignorance perhaps. Before typifying a comment as ignorance, check the facts, or at least verify the conjecture.


Impressive thread, except for Neil's little meltdown.

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