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Cost per mile to drive S versus comparable cost per mile with a gasoline equivalent?

Let's compare conventional gas cars and electric (S) cars in terms of dollars per mile (US), which is what the bulk of the world will care about.

Gas is about $4 US / gallon where I live. Say my car gets 20 miles / gallon. Ratio these and you get

$4 US / gallon
----------------- = $0.20 / mile = G <-- call it G for cost to drive per mile using gas
20 miles / gallon

What's the number for an S, measured as follows:

$X US / unit of charge
-------------------------- = $X/Y / mile = S <-- call it S for cost to drive per mile using electricity
Y miles / unit of charge

Is S > G or is S < G? In other words, does it cost more per mile to drive an S than my car (focusing on fuel only)? Or, is the reverse true? Is this information somewhere on the Tesla website? Where exactly?


Electricity is cheap. You could say that "S << G".

It takes about 300Wh to drive one mile (250Wh at 60mph with Roadster). If you pay $0.1 for kW that's then $0.03.

"...$0.1 for kWh..." not kW. Edit-button, where are you...

$0.08342 / kWh is the net cost where I live, including real-world fuel adjustment charge, regulatory, yadda, yadda,...

$0.083 / kWh
====================================== = $0.025 / mile
1 mile / 0.300 kWh (note unit change)

So, this is an order of magnitude cheaper (x10), at my local electricity rate, to drive the S compared to my current car. Hum... This does not include the hike factor for using more power to charge the car every night, which will likely significantly impact my savings. What will this be in 5 years when 10% or more people own electric cars in my neighborhood? My local infrastructure grid can't handle power reliably now (cars on it are not feasible in the long run--yes, I'm an EE ;o). I like the idea of charging the car while I drive it or park it in the sunlight (all of southern USA)--for free and not largely dependent on grid power. I did not see a sunroof sunlight charging option for the Tesla. Makes practical sense and I believe I've seen this concept implemented in the not-too-distant past on an e-car (where?). Yes, I love the idea of x10 less cost of the Tesla over a comparable gas car. Now how about an SUV the size of a CRV or RAV4? Anything in the works? This is another thread ;o]

World doesn't need much more electricity generation in switch to EV:s, but local distribution networks might need a rework. Reason why you wont need much more electricity for EV:s is that refining gallon of gasoline takes about 6kWh of electricity. That's 20mile worth of driving in EV, so your current ICE car is actually using same amount of electricity as EV.

Timo, I knew this approximative figure of electric energy consumption for refining gas, but I could not find an explicit / easy to read estimate. I just need it for some naysayers, do you happen to have a link ?

I did not see a sunroof sunlight charging option for the Tesla. Makes practical sense and I believe I've seen this concept implemented in the not-too-distant past on an e-car (where?). (bmckinle)

You may be referring to the Fisker Karma. It has some photo voltaic installed on its roof, but the opinion here in the Tesla forum is that its merely for coolness and (pseudo) green image. The amount of electricity generated by a photo voltaic area as small as the roof of a passenger car is so small, that a) it is not really good for anything except maybe running an additional fan while the car is sitting in the sun, and b) if you want to run an additional fan you could as well draw the power from the main battery which would not be affected much. Photo voltaic cells need to be produced, integrated into the car's electricity, and maintained -- at the current state of technology, it does not seem worth the trouble.

@Nicu, no I just googled for information. One of the links had a direct post from some official department which then was used for math to get that conclusion. If I saved that link it is in my other computer, not this one. I don't think I saved it.

Found it.

Some other links claim numbers up to 15kWh, but I think those are quite a bit exaggerated.

Yeah, I just found the same link. However, it does not say that 6kWh of electricity are spent to refine crude oil to a gallon of gasoline. It says:

Thus, using an 85% refinery efficiency and the aforementioned conversion factors, it can be estimated that about 21,000 Btu — the equivalent of 6 kWh — of energy are lost per gallon of gasoline refined

which merely means that the refinery process is not 100% efficient and the source crude oil carries more energy than the resulting gasoline. In particular, this does not mean that readily available electricity is consumed, which could as well be consumed by an electric car. It is just a mathematical equivalent -- if you want to use that energy in an electric car, you have to convert it into electricity first, which typically is less than 85% efficient. So either I got it completely backwards or the argument is irrelevant at best. You could also call it misleading.

You can get down into the weeds figuring out cost of an EV vs. ICE (as I have). There are numerous factors such as fuel, maintenance, reliability, battery replacement, etc. What I've found is that when everything is accounted for, both types have approximately equivalent total cost of ownership. Typically the EV will cost more initially, then have considerably saving compared to the ICE until the battery needs replacing, which ends up wiping out the saving.

Hopefully, as the ever critical $/Killowatt Hour figure continues to decline, and as gas prices climb, EV's will gain ground over ICE's in this regard.

I read that as "this much energy is put to the process to generate end products".

Sad fact is that exact numbers how much of that is actually electricity is unknown. I think nobody knows, of if they do that data is well buried and hidden. It is a really complex thing to calculate how much electricity goes to gasoline and diesel leaving everything else out. Look it this way and get that result, look it that way and get this result. Difficult thing to agree upon.

There are other links that use different numbers, some of them refer to natural gas used to refine in addition to electricity, but then you need to consider using that same natural gas to produce electricity instead, in which case you get a bit higher number than 6kWh. Also extracting oil seems to require a lot of energy.

It varies a lot.

This is interesting reading:

From that it look like refining one gallon of CARB gasoline uses around 1kWh pure electricity, if I counted that correctly, however refining entire barrel of oil to end-products uses a lot more, and I don't know how tightly those other products are tied to refining process in whole.

After doing my math, a 300mi battery is a necessity for me. About 70% of my driving is highway. Here in Florida, the highway speed limit is 70mph (mostly). However, most cars are cruising at 75mph.

I looked at a graph on the Tesla website which shows that at a constant speed of 55mph, the Roadster will have a range of about 245mi. However, at 75mph, the range drops to about 160mi. That 35% hit gives the 230mi battery a useful range of about 150mi on the highway. I was hoping for a useful range of at least 200mi of highway driving.

Remember the saying: "Your actual mileage will vary".

Here's the page with the graph I was referring to:

Don't forget that the off peak electricity is effectively "wasted", since demand for power is generally less overnight than it is during the day. If most people only charged at night, the existing grid could easily handle it, since the demand wouldn't exceed the daily usage.

How long will 300 mi battery last at 40 commute miles per day at 70 mph? 1 year? 2 years? Just a rough idea.

I live in San Antonio, so where would I get the battery changed? There's no Tesla dealer, although this city is the second largest in Texas, next to Houston (no, its not Dallas).

If you treat your battery well, you will have about 70-80% of capacity left after 7 years.

I agree with qwk.

With the 300mi battery pack, you should still have at least a 210 mile range after 7 or 8 years of use. At that point, you could trade the car for a new model, or have Tesla update it with a new technology 300+ mile battery pack which (by that time)should cost less than $10K including labor.

The big question is: what kind of trade-in value will you have on a car with a 210 mile range after 7 years? The last car I kept for 7 years was a Toyota. CarMax bought it for 30% of the original value.

The grid capacity argument can be compared with the gasoline supply network for the early ICE cars. In the late 1800, gasoline was mostly sold in pharmacies! That didn't stop the creation of the ICE automobile industry.

In comparison, we are ahead of that: there is a well-developed electrical grid, far reaching. The demand for electricity for charging EV cars will not skyrocket overnight. Just as the ICE cars did not multiply to millions overnight, EVs will gradually fill the market. The electrical energy transport is a mature technology and business, that constantly adjusts capacity to demand, i.e. air-conditioning units are added in new developments in much higher rates...

"hike" factor for charging at night?? That sounds absolutely inane. MORE charges at the off-peak period? Where on Earth do you live? Even Ca isn't that crazy.

@Vawlkus: While you're right that the capacity during off-peak periods is "wasted," the electricity isn't -- it's simply not generated. Grid operators continuously match generation to consumption (plus losses), so it's not as though these off-peak kWhs are being dumped somewhere: generating them still requires burning incremental fuel.

As the generation fleet becomes more saturated with renewables, like wind and ocean technologies, we could actually get to a point where we are "dumping" power overnight. That's where storage technologies -- either dedicated storage, or EV batteries -- would be most valuable.

I live in the NW and right now the wind generation businesses are complaining that they have more capacity than the distribution can sell because the distribution companies are already getting more hydro generation than they have demand for. Without storage or better lines to sell it to the rest of the country power is being wasted. It never gets turned into electricity but it just blows over the windfarm without generating anything. This is primarily a spring problem I think. Spring wind are high and winter snow melt is copious.

Similar with nuclear plants: You cannot turn them on and off at will. Shutting down a nuclear plant is a matter of days, restarting it may take even longer. And a lot of energy is wasted when the plant is shut down with fuel rods burnt only halfway. Thus, you do not shut down nuclear power, and the electricity must go somewhere.

The crucial difference between nuclear and wind/solar (besides considerations like cost, safety and environment) is the nuclear delivers electricity at a constant, predictable rate whereas wind/solar is to a large degree unpredictable. But they have in common that is does not make any sense to shut them down when demand decreases temporarily.

It is a bit different with charcoal, and it is fundamentally different with gas turbines. The latter can in fact be tuned up and down to match demand within very little time.

Quite right, Volker. Many types of power generation cannot be easily ramped down, especially nuclear.

Here in Ontario on some days they've actually had to PAY nearby American utilities to take their excess power.

No, that's not a mistake! Power trading is a market system and the price can actually go negative if everyone has too much capacity online at the same time. If the only alternative is grid instability or scramming a nuke, you'll gladly pay for the "service" of someone else taking your power.

The incentive programs for green energy here also can result in people being paid not to produce electricity.

Here's a real-world example. I commute 55 miles round trip per day. My 2006 Corvette would burn 2.5 gallons of premium unleaded to make that journey. At $4.50/gallon that's $11.25/trip. When charging overnight at $0.06/kWh (00:00-07:00 rate) my Roadster costs $0.96 to make the same trip.

@Douglas, actually coal is even slower to ramp down. It just simply takes time to coal to burn out. Nuclear is easier to ramp down, you can shut down the reactor in matter of seconds but it too takes time just because already released heat cannot simply disappear and water in them needs to go on circulating, otherwise you overheat the reactor and then that "shut down" doesn't apply anymore.

You could adjust the energy generation quite quickly by simple turbine bypass valve, but not generating energy is money-losing process, so that is not done.


Yes you can shut down nuclear instantly, but you can't restart them quickly.

When the Northeast blackout of 2003 hit, most of the reactors in Ontario scrammed. Three units at the Bruce Nuclear Plant did have a steam bypass system that allowed them to continue running at 60% power and were back powering the local grid in five hours. The rest were down for days, because they had to wait for reaction products to decay before they could be safely restarted. We had rolling blackouts for a week after power was restored, because most of the nuclear plants were still offline.

Missing the point. Every renewable generation system MUST be backed up fully (=100%) by conventional, because it can and does go to 0 (zero) at very inconvenient times. It is fundamentally useless for base load -- which is actually the most important.

Further, ramping gas turbines up and down keeps them in their least efficient power modes much of the time, and is very hard on the hardware.

I.e.: renewables generation is currently an exercise in enforced economic and ergonomic stupidity.

It will always remain so, because it is diffuse and its massive hardware and real-estate, transmission, back-up, and storage requirements are ineluctable.

Not every. Geothermal systems are immune to all changes other renewable systems are. Hydro is also very reliable. Probably more reliable than most non-renewables.

Yes, though geothermal is "renewable" only at the rate at which heat "refills" the rock in contact with the underground piping. This rate is easily exceeded by the power draw in most areas; only a few "hot spots" have enough flux to generate respectable power. And the chemicals used in the large plants are less than benign. Not much potential to defray real world energy requirements there.

As for hydro, it's great where available in sufficient quantity, and the containment valleys are expendable. I live in B.C., Canada, which has the vast majority of its power from hydro. Yet even here the greenies are pushing to stop its use and switch to wind etc. In Spain and elsewhere, they like to count it as (the only actual high performance) part of their stats, but in general they exclude it from the classification. Certainly, there is no push anywhere to expand it. In the UK, aside from some trivial gestures in Scotland, sure to mess up substantial areas of the Highlands, it's barely on the radar. And I doubt you'd find many waxing poetic over the Three Gorges project on the Yangtze.

In fact, in many areas there's a push to demolish dams and return rivers to their "natural state". Often these are obsolete and expendible structures, but even in the NW there's been talk of completely undamming the Columbia, etc., which is not trivial.

So, if anything, hydro has a rather negative "cachet" in the Renewables World. As Australia and other venues are discovering, wide swings in rainfall patterns occur which play Hobb with planning for it, too.

So it's rather disingenuous to fall back on geo and hydro to justify renewables. If they were the actual subject of discussion, the debate would be far different world-wide, and many billions of dollars would have been rescued from the Rat Hole.

In geothermal case it is "only" matter of getting deep enough to get steady energy flow as long as you want anywhere in the world. Obviously that "deep enough" is different in different places, so if you happen to live place with think crust getting deep enough can be rather challenging.

The full potential of geothermal has not been taken seriously until very recently, probably because other methods have been so cheap. Because of that equipments to get deep enough are also quite primitive.

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