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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.




Built in the UK by Lotus but won't be available here. Nice one.


This is now a direct competitor to Hybrid Technologies electric Mullen GT/LiX-75, both priced approx the same ( LiX-75 was around $125K )

I wonder when will we see a major motor magazine doing a one on one race between those two ?


SWEET!!! ... now I just need to pull 100K out of my back pocket. ... guess I'll have to wait for the family sedan ... sigh

Mark A

Catering to Jay Leno and George Clooney type of buyers, maybe the only buyers!

Max Reid

250 mile (400 km) range is impressive, but 285 hp is not needed. They can reduce the 285 hp and the cost. That where the production volume will go up.


Max, it's a sports car.


Wired story and some other actually quote $80K pricetag. And they have a sedan in the pipeline for 2008

Comeon, we want to see a face off between Venturi Fetish, Hybrid Tech LiX-75 and this beast already.

Which one is the most "silent but deadly?"

Harvey D.

The future belongs to EVs.


Well here we go again, another carrot to dangle in front of us and then we can't afford it. I read that they want early adopter for this car and that's the only people that will buy it. What kind of crap is that? The electric car isn't a brand new invention! It doesn't need early adopters unless they are 120 years old! The EV has been around longer than the gasoline car. We need products the general masses can afford, not the 'hoidy toidy'. Please, they can afford the gasoline in the first place. And spare the rethoric about saving the planet, the rich aren't interested in that, they want little toys to play with, while the rest of the world needs real solutions that everyone can afford. Bad marketing Tesla...but good product! Please come out with something soon!
I guess they didn't consult a real marketing firm. Every car maker starts by making an introductory car that cost little. Remember the Honda Civic? Kia didn't start with a $100k car! Nisan's car was a gas miser and it didn't cost much. Hey it just goes to show money doesn't make you smart!

allen Z

Dang It! GM could have been comparably far along by now if they had not killed their EV-1. Resized and revamped EV-1s (with or without a small ICE) could have served 3/4 of the population, while a juiced up version could satisfy the speed demons. The rest would be served by station wagons, minivans, crossovers, and light trucks.
___On the other hand, it would be like hitting the jackpot for electric utilities. They might get better efficiencies out of their powerplants by running them at optimum rates, but in the end, you would likely have seen an enormous rise in coal usage.

allen Z

Max; James,
Perhaps a variable driving profile software patch. Some sports cars already have tehm to specify what the driving/ handling is going to be like. They regulate power, torque, ride/suspension height and stiffness, handling, and traction control. It may be possible to lower the power for the motor. That way, you may increase range. This car may fit with a long commute, ie 100+ miles.
___It may fit with a drive 4-5 hours, stop for 4, drive another 2 a day long distance travel plan. However, until faster charging, higher capacity batteries come online, this is not for rapid cross country road trips.


I think a lot of people here are missing the point.

This car is supposed to change the idea in the mind of the public at large of what an EV can do. Not only does the Tesla look good, but it has a long range.

Yes, it's $80k and not an econobox. But you tell me what battery technology they can use to make a car that costs $15,000 and has a similar range.

If this car sells, the money they make will fund new models and new technologies. They already have a sedan on the drawing board. The Tesla is a marketing tool, and I think a very good debut.

Richard: The problem with EVs has always been batteries. They simply cannot compete in terms of convienience (long charge times), energy density (low range), and cost to liquid fuels. Until those problems are fixed, the market will remain limited.


As I said elsewhere the rich will get fuel cell and exotic ev cars and the less well off will make do with put put cars.


Thanks for the insight Cervus,
but electric cars have been around for a century now. There is a substantial market for these cars as the Rav4 following can attest to. There is a huge line of people that would love to own one, and they are a decade old! There is very little mentality change needed for the amount of cars that need to be produced to fill the demand! The rest will learn as the cars filter into our lives and the drivers of such cars will easily explain that you don't 'fill-up' once a week, like gasoline engines, but rather you plug in at night, or anytime and fill up as you rest. The only perception that must be changed is the range. As we know, most people drive only 30 miles per day. This makes a great car for 95% of all driving needs. Even if you drive over 50 miles a day, it still is a great car. When you have to go longer, then rent a car or take the train or fly!
But, what sense does it make to have 20 $100k cars on the road when you could have 100,000 $20k? Which is better for the econoly/enviroment/etc? The choice is clear, and I will continue to wait for a logical solution.


Actually, car companies start out two ways.
1. Cheap econobox (most)
2. Expensive toy (Ferrari, Lambroghini, Koenisegg, etc.)

This car, as someone already said, is designed to change perception. If we can get some momentum behind the EV concept, good things will follow. You keep a carrot dangled in front of the public long enough, make it pretty and shiny enough, and make them want it, they will start a demand. The supply will follow.

The challenges that batteries hold can be overcome. We just need to be creative and take patents back from the oil companies regarding superconductors.



My understanding of battery technology is that it is still very expensive to get a decent range. The RAV4 EV's battery pack alone costs something like $25,000. Replacing a Prius's pack is about $7,000. These are huge costs, which is why the Obvio EV in the earlier GCC story costs $60k to get a similar range for the Tesla.

In short, there is no way you can make an EV that sells for $20k or less and actually turn a profit. So if you're going to make an EV that's have to cost at least $60k, you might as well do what Tesla did and make it an exciting, handsome sports car that will stir the public interest while turning a profit at the same time, if it sells.

Tesla's technology is innovative because they're using batteries that you'd normally find on laptops. In other words, this car is benefiting from advances in the conusmer electronics industry. I'm sure there will be more advances. But it will take invesment capital, and selling these cool-looking sports cars to fund them.

Established companies ignore the changing marketplace at their peril. Sometimes conditions are right for an unknown, fast-moving company to exploit what was previously ignored. Japanese automakers did that in the 70s by providing the fuel efficient small cars that US automakers had trouble with. Whether Tesla is in a similar situation Honda and Toyota were in the 70s, well, we'll see how well their cars sell.


original Lotus Elise owners, which this car is derived of, are exstatic over the styling of this one, and basically everybody is saying that they would buy one in a heartbeat.


Look at it another way: The Tesla (and some other EVs) may be the end-of-the-road for those other hot (ICE) sports cars, such as the Ferrari, Lambroghini, Koenisegg, etc.


Let's not forget we still have lead acid batteries that work very well, allbeit heavy, but reliable!
Many conversions have been done from regular gas cars, and some done very well! They use lead acid.
There are also some companies making electric Neighborhood vehicles. I can't use one because I travel too far and those are just not practical. They use lead acid batteries! The battery issue is perceived. Let's get some solutions out!

Joseph Willemssen

The future belongs to EVs.

Not on tires.

tom deplume

Seems to me the same power train could be used in a full size luxury car and still get 100 mile range. Paying $100k for an overpowered toy is silly. A $100k for a luxury daily driver is something I could go for if I had an extra $100k laying around.


If it had "only" a 100mile range the perception of the average American would be that it is inferior and incapable.

If you used lead-acid batteries handling would go down the drain. Please bring an EV converted vehicle to an autocross session and drive the same vehicle non-converted. Now imagine you need to do an emergency lane change because someone cut you off. Designing with lead acid from the ground up changes things a bit but not by much if you want a range that consumers perceive as acceptable.


Another issue, especially where it relates to range and recharge time, is designing for peak usage.

This problem is illustrated with the design of the current electricity generation infrastructure. If they only had the capacity for average daily usage, the whole system would come down every time there was a heat wave.

My daily commute is 60 miles roundtrip. A 100 mile range for an EV would fit that nicely. Except... last year I drove to a conference that was 124 miles away. And then there's the vacation to Yosemite I'd like to take sometime. And I might want to go up to LA again sometime soon and visit family.

For any one of those things I'd have to rent a gasoline car, at additional time, expense, and inconvenience.

My point here is that while the majority of my driving might just be the daily commute, my choice in transporation is also influenced by what the vehicle can do if I need it to. I might be able to charge up an EV in my garage at night, but there may not be a plug on the other end I can use. And I don't want to risk being stuck on the road and having to wait for hours while it recharges.


I think the idea with selling electric cars with limited range is that initially at least they will be purchased as second, pure commuting or local driving cars. I guess most families these days have more than one car? Also I think if you are rich enough to buy a $50K or $80K limited range car you will probably also already own (and not want to sell) a gas car for longer trips. As this situation becomes more common people hopefully will start to sell electrical recharging services and batteries will be developed that can be recharged in 5 mins. Its a gradual process.


Performance electric cars were fascinating toys for enthusiasts for years. Their owners just liked to smoke Mercedes at traffic light. Elise is great car by itself, and electric Elise which can smoke Ferrari at traffic light will be fascinating toy for rich people. Do not forget, that third of great technological breakthrough initially were rich people toys (other third being military developments).

Their marketing for potential buyers is brilliant: good looking small car (totally against perception for both small econoboxes and big performance/luxury quarter million road yachts) with environmental twist. High price in the targeted buyers market is not disadvantage: they exploiting “Rolex” psychology of the rich – “my toy is even more expensive then yours”. I bet exclusive model at price tag of QM is under way, with “military grade titanium stainless body chromed by gold”. If they stay this way and do not try to jump over their own head to produce mass-production EV (which is not possible with current technology) – the mistake done by GM, they will be financially successful. Two their principal backers, the guys who founded Google, probably showed them example how to think out of the box.

Couple of technological clarifications. Any electric motor can produce triple power for couple of seconds before overheating become a problem. I bet their 185 KW output is peak output, rated output being close to 80 KW. This works perfectly well for public road car driving cycle.

2.18km per 1MJ is equivalent of about 8km per KW*h. Efficiency of electric generation in US is closer to 38%, not 53% they are using for calculations. Plug-in Prius will have same efficiency as electric car, but additionally will have “gasoline engine range extender”.

Any rotational motor (IC or electric) have its momentary power output and momentary torque bounded by formula:

Power = Torque * RPS *2Pi, W = N*m * s^-1,

where Power is measured in W, Torque in N*m, RPS is rotations per second, 2Pi is approximately 6.28.

As you can see, talks about high torque at high rpm is BS.

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