Tesla Model S 60kWh Gets Official EPA Ratings | Hacker News Reader

Tesla Model S 60kWh Gets Official EPA Ratings

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47 pointsMikeCapone48 comments

So the MPG rating is based on the power plant emissions per mile's worth of energy consumed by the vehicle and comparing that with gasoline emissions?

That's great, but like most consumers I want the MPG based on miles per dollars. For example, if I can drive 100 miles on ~$3.50 worth of electricity (or whatever a gallon of gas costs these days), it would be comparable to 100 mpg. Does Tesla or anyone else put out these numbers?

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The article claims the 60 kwh model goes one mile on 0.35 kwh. So, at USD$0.16662/kwh (didn't know the currencies were that close), it costs $0.058317 to go a mile. If gas is $3.35/gal, then you need to be getting 57.4 mpg to be even.

However, if, as was quoted up thread, off-peak electricity is 5¢ per kwh, then the equivalent mpg jumps to 191.

> So the MPG rating is based on the power plant emissions per mile's worth of energy consumed by the vehicle and comparing that with gasoline emissions?

This sentence appears to be very, very confused. It's not based on emissions at all. It's not energy per mile. And it's not MPG, but MPGe.

"MPGe" is "Miles Per Gasoline Equivalent", and is not MPG. This is an odd historical measure of engine efficiency which stems from early attempts to shoehorn natural gas vehicles into CAFE standards. For purposes here, I believe what the EPA did is take the energy contained in one gallon of gasoline (33.7 kW-hr) and computed how many miles an electric vehicle would go when consuming that amount of energy put into its battery. It's useful for comparing electric vehicles to electric vehicles, but not useful for comparing across different kinds of propulsion.

What you probably want is Miles per Dollar. This would have to be computed both for your gas car and your electric car, and has to be computed based on the cost of gasoline in your area, the efficiency of your two cars, and the cost of night electricity (most utilities have night-consumption plans for electric vehicles).

But my understanding is: at present most people see their electric vehicles costing about 1/3 per mile of a gas vehicle. That doesn't take into consideration the generally lower costs of maintenance as well (gas engines are complex).

Wouldn't that be a bit too variable to estimate? If you charge your car during the day, it would cost a lot more than charging at night. I think in the bay area, it's around 5 cents per kWh in commercial zones during off-peak hours, so a full "tank" for the 60kWh battery pack would cost you around $3 -- that's almost the cost of half a gallon of gas!

When everyone starts to buy electric cars, won't we start getting closer to 24 peak hours a day?

Interesting question! Obviously this isn't a problem that's going to happen any time soon. But if you look at a random day of usage for the California ISO (actually, the only one I could find) [1], peak load was 30,000 MW and between midnight and 6AM load was around 22,000 MW. So that's 48,000 MWh, or 48,000,000 KWh, and at 100miles/38KWh, that's 126 million miles of excess capacity in those hours on the West coast. If the average commute is ~30 miles round trip, that's 4 million commuters in California, just from current excess capacity at night time.

Needless to say, it will be a while before Tesla ships 1 million cars in California, much less 4 million.

http://www.ferc.gov/market-oversight/mkt-electric/california...

Even if we did, that would be good for the grid. Many power-generation technologies have high start-up and shut-down costs, and are most economical when they can be run 24/7. If we can get the variability of power demand lower, we can generate more power with economical means, and use less of the more-expensive and polluting methods.

For the 60 kwh model, 60 kwh would go 171 miles, so that's 1.75¢ per mile. (Although Tesla claims a range of 300 miles at 55 mph.)

I didn't know off-peak rates were so cheap.

$4 - $8 per 100 mi.

Using 38 kWh/100 mi (from the article), and estimating electricity to be .1-.2 USD/kWh from here: https://en.wikipedia.org/wiki/Electricity_pricing#Global_ele...

No, MPGe is based on 33.7 kw hours = 1 gallon of gas. It's trying to measure based on energy efficiency, not pollution, and not cost to the driver per mile.

The article claims 38 kwh to go 100 miles for the 85 kwh model. So, if a kwh is a dime, that's 3.8¢ per mile.

The 85 kwh model does 0 to 60 in 4.4 seconds. How many miles per gallon would a comparable gasoline powered street rocket get? Maybe 15 or 20 if you are lucky? Let's be optimistic and say 20. Then, if gas is $3.75, that's 18.75¢ per mile, or about five times the expense.

The appropriate car to compare the Model S to is probably a BMW M5, so yeah, in the 17-22 mpg neighborhood.

Modern sports or performance cars (audi, porsche, etc..) get around 20 city and 27 highway these days. Though, the Tesla is still much more cost efficient.

Local gas and electricity prices vary dramatically, but it should be fairly simple to calculate this yourself for your area.

Anyone know the weight difference between the three configurations? Haven't found it anywhere.

The curb weight of the 85 kWh model is 4,647 lbs, I wonder how much of that is the battery.

I suspect the weight to be the main difference in efficiency, though each configuration (as well as the 85 kWh performance version) has different specs for Peak Motor Power and Peak Motor Torque.

Also, I wonder if power/torque differences between models are because they're using a different powertrain in each model or if it's an electrical (or perhaps software) limitation.

I'd love to know if anybody knows more about these things...

This doesn't really address your questions but it's interesting none the less. I talked to a rep at a Tesla showroom. Surprisingly, the models seem to all weigh the same amount. The weight was maintained a specific number so the car could maintain it's 5 star crash test rating... He speculated that some of the weight was in the form of actual weights.

>He speculated that some of the weight was in the form of actual weights.

If true, that would appear to suggest an obvious after-market performance mod.

> an obvious after-market performance mod.

With the probable traditionally detrimental effects on ride and handling.

That is enormously unlikely.

More likely to be the battery pack. You can trade kWh for manufacturability and materials cost.

who knows, maybe they all use the identical motor, but there's a few solder bridges that prevent you from going as fast as the expensive models... cars that can be overclocked would be interesting.

Calling such cars "overclocked" would be just as technically apt as calling clock-speed enhanced CPUs "turbo."

My 286 had a turbo button that bumped it from 8MHz to 10MHz.

It was just as terrible then as it is now.

The "MPGe" thing seems very silly, particularly since if I were using this car 99% of it's power could be coming from hydro/nuclear/wind. Surely there must be a better way of comparing efficiency and environmental friendliness.

> if I were using this car 99% of it's power could be coming from hydro/nuclear/wind.

Actually, solar, since that's what is powering the free Supercharger network going up over the next few years: http://www.teslamotors.com/supercharger

Fair enough, though with my usage patterns most of the charging would be done in my garage. ;)

Which is why they will probably partner with solar city to get people hooked on solar panels for the home. The convergence of falling costs for solar panels and falling costs for electric cars with increased range will probably reach a critical mass similar to the Internet in the 90s and an enormous boost to the economy from the recaptured opportunity cost being consumed by internal combustion engines.

Not to mention, the super chargers are an excellent testing ground for newer technology like super capacitors that use graphene. They can dog food improvements to the storage mediums without actually risking it in the power train.

they can dog food improvements

What?

Software term. Means they can work the bugs out themselves before integrating it into a product sold directly to the customer. At least, that's what I would do.

http://en.wikipedia.org/wiki/Eating_your_own_dog_food

Agreed. There are quite a few motorcycles that can get around 95 mpg. It would still cost around $18 for a full tank of gas in a motorcycle, but probably only $3 for a full tank in the tesla. If they based mpg on dollars spent per distance provided, the tesla would get around 550 mpg.

Well on a cost basis you can use this formula to compare the cost to a gallon of gas: ((kwh electricity cost)/(charging efficiency percentage))*34.02 . Then on a real cost basis you can compare the cost of an 'electric gallon' and an electric cars MPGe to your 'gas gallon' and your gas car's MPG.

In the bay area, ironically enough, with residential electricity being around ~0.30/kwh, an 'electric gallon' is around the price of a 'gas gallon'.

https://en.wikipedia.org/wiki/Miles_per_gallon_gasoline_equi...

In reality, once you get to a certain level of efficiency, it's something of a moot point anyway. Both money-wise and emission-wise, there are likely much costlier areas to focus your efficiency increasing efforts than your vehicle.

(Range, on the other hand, still has large gains to be had.)

Yeah, I guess an issue is getting consumers to understand that while a high MPG is better than a low MPG, having no MPG is even better. Consumers want easy presentable numbers to compare, so they can feel like they have a grasp on the difference.

Still too expensive and too limited for my taste but I guess someone will buy it.

In Canada there is such long distances between towns and cities I can't imagine being limited to 480km ideal would be 1,000km. The deal breaker (besides the $70,000)is not being able to charge it except at home even at 5 hours with the 20KW charger is still too long.

Plus living in a snowy land where in winter you can see your gas gauge move you use so much fuel heating the car, spinning wheels, knobby snow tires.

People seem to see vehicles as just another device like a new phone or TV I don't doubt they'll become more popular and drop in price.

> Still too expensive and too limited for my taste but I guess someone will buy it.

> . . . I don't doubt they'll become more popular and drop in price.

That's exactly Telsa's (stated) plan.

Phase 1 was the Roadster. The Roadster was made in small numbers, using very "hands on" construction methods. It was very expensive, but it was designed to feel and perform like a very high end vehicle. For people who can drop $150k on a car (and there are more of those sorts of people than you might think), the Roadster was a very competitive option

Phase 2 is the Model S. The production line for the Model S is a lot more automated, and production runs are larger, resulting in a vehicle that is fairly competitive "mid range" luxury vehicles (e.g. the BMW 6 series).

Phase 3 will be a more "average consumer" targeted vehicle. Taking advantage of the lessons learned (and to some extent, the capital raised) in the first two phases.

Nissan is already doing that with the Leaf but it's still too limited I think only ~120km-160km per full charge. Although I do like the solar panel roof option to trickle charge the car's batteries.

The ~160km is misleading though because heating the car in winter and in southern climates cooling the car must require a lot of power.

Phase 2a Model S

Phase 2b Model X

At some point there is supposed to be a refresh of Roadster (model R) using the model S drive train. Probably itching to make the car for the masses the Tesla Model T (trademarked?).

This is really strange, at the factory test drive last year I spoke with the head of engineering on the Model S and he said the battery backs for 60 and 85kWh were the same size but with different formulations.

Only the 40kWh was supposed to have a smaller battery pack, in fact if you upgraded the 40kWh pack you'd need to change the suspension.

Trying to wrap my head around these numbers, I see the rate 35 KWh / 100 miles which suggests to me you could take a 100 mile drive for about $4.50 (11 cents per KWh and 15% extra for charging inefficiency)

Yes, that's right... Electric cars are generally cheaper per mile to run.

But power rates vary wildly all over the place, so your running cost and mine might be a factor of 2x-3x different.

For us in california, normal PG&E rates go up to $0.30/KWh and beyond in an average household (they are tiered like income tax rates are).

But with an electric car, you are eligible for a time-of-use metering plan, where night-time (12 midnight to 7am) is very cheap -- $0.05-$0.09 per KWh -- but weekday daytime in the summer is painful at ~$0.50 per KWh. So if you remember to set a timer to charge at night, it's cheap!

You can look at http://en.wikipedia.org/wiki/Electricity_pricing and sort the table by pricing to get a sense of the huge variance in electricity costs around the world.

Yes, so in the more typical 3 gallons of gas car (33.3 mpg) that would set you back $9-$12 you pay half as much for the energy But electricity, like gas prices, varies.

A more interesting way to look at it from my perspective is that each 'mile' has an energy cost of 4.5 cents vs 9 cents. And in a 10,000 mile year that is $450 not spent.

There are still a lot of unknowns in terms to total cost of ownership, battery pack replacement, other maintenance.

edit: $450! Just made it in under the wire. Thanks.

That's a difference of $450, not $4,500.

I don't quite understand. Where do environmental factors come into play with MPGe? I thought its a plain measure of energy.

Remember that the "G" in "MPG" stands for "gallons" (of gasoline or diesel fuel). When your car runs on electricity, the measurement no longer applies directly, so a conversion is used to treat "gallons" as a proxy for pollution.

I don't think it's pollution they're looking at here: it's cost. E.g. the cost to go the equivalent distance as the cost of a gallon for an otherwise equivalent car. Perhaps I'm wrong. But bringing emissions in adds significant value to the electric option: value not yet realized since externalities like CO2 emissions are not currently paid for.

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