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Cost to fill

So I have been trying to calculate the cost to "fill" an empty "tank". Here is my math. It seems low, help me find the error... Or spread the good word!

Power per mile: 300Wh (per FAQ)
Miles per "tank": 300 miles
Power per "tank": 90 kWh = 300 * 300 / 1000
Cost per kWh: $0.09 (in NC, varies by location)

Cost to "fill-er-up": $8.10

Dear Zelaza, Why are you wasting OUR time on this forum, get lost!

@leebuck, no that's about right. Some people are saying 85kWh, others are saying 95kWh, but your number is as good as any.

Here in WA state, I'm paying $0.064/kWh so it would cost $5.76 to fill up. So even if you have high electric rates, it's still 10% (or thereabouts), of the cost of petrol.

The Tesla people said "85 kWh is what we have been told to say.". They would not clarify usable, nominal, etc.

There is some loss with the charge. Thus 100 kWh is what I would suggest is the best estimate to use. It also makes for the easiest math.

By the way the three hundred mile battery will last longer than the smaller sizes. The loss of charging ability is affected by time and use. Use is affected mostly by the number of cycles. A larger capacity means fewer cycles. Thus longer life.

Just in case someone takes Zelaza numbers as fact, $40k battery change is BullS*it. Real number will be closer to $4000 than $40k after 100000 or five years.

If you plug it in every night, won't the number of cycles be the same? Or should I treat the battery pack like a gas tank and only plug it in when it needs to be filled up?

If you plug it in every night, won't the number of cycles be the same?

No (or yes depending what you mean by "same"). Cycles are counted from empty to full to back to empty. If you fill only half battery that counts as half-cycle.

If you have 300 mile battery pack and drive 60miles a day each day counts as 60/300 = 0.2 cycles. If it is 160 mile pack then it is 60/160 = 0.375 cycles.

@ Timo

You never in your lifetime get anything highly engineered that weights 400 kg (900 lb or so) for $4000 (not to mention inflation with all the money printing going on on the other side of the pond).

[...] all the money printing going on on the other side of the pond. (Nicu)

I would greatly appreciate to keep political topics out. Most Europeans also have opinions regarding American economic and financial policy which I advisedly not mention here. (And yeah, it's a great fuck-up. On either side of the pond.)

Or should I treat the battery pack like a gas tank and only plug it in when it needs to be filled up? (Mycroft)

No. The Roadster's user manual is clear about this, and I except there will be similar instructions for the Model S.

except -> expect

Volker made me curious, so I found the Roadster text:

Designed to be plugged in

The Tesla Roadster is designed to be plugged
in when not in use. This ensures that the next
time you use the vehicle, it is fully charged
and ready to go. There is no advantage to
waiting until battery level is low before
charging. Plugging in every night eliminates
the risk of damage that could be caused by
over-discharging the battery.

When plugged in, the vehicle optimizes the
lifetime of the Battery by managing its
charge level and temperature. The vehicle
wakes up every 24 hours and, if needed,
automatically initiates the charging process
to keep the Battery at an optimum charge

Thanks guys. That clears that up.

@Timo writes:

"Just in case someone takes Zelaza numbers as fact, $40k battery change is BullS*it. Real number will be closer to $4000 than $40k after 100000 or five years."


(1) VERY HIGH ESTIMATE: Currently battery can be priced at about $700/kWh. For a 95 kWh battery this comes to $66,500. No one would ever buy this so if we assume half this price the cost of the 95 kWh (300 mile) battery comes to $33,250. What the actual price may be I can't possibly tell.

(2) ESTIMATE BASED ON TESLA NUMBERS: Adding battery to extend range of Model S by 140 miles = $20,000. Therefore, 300 mile battery comes to (300/140)x$20,000 = $42857.+. This comes from Tesla's numbers, not mine.

(3) ROADSTER REPLACEMENT BATTERY COST: Another contributor in these forums noted (in another thread) that you can RESERVE a Roadster battery for $12,000. I can't confirm this nor have any other information about this. The Roadster battery capacity is (I believe) 53 kWh. Therefore, a 95 kWh battery at these costs becomes (95/53)*$12,000 = $21,509.+. I'm not sure what Reserving means, perhaps you have to pay this in advance when you buy the car, or something else. Whatever, I'm sure it would increase the $21,000+ cost just calculated.

I think that $4000 for a 95 kWh battery is a little low; by a lot.

As usual, the truth of battery costs is somewhere in between the extreme examples people give. I have no idea how much lower prices will be 5 years from now, but I can give you an idea how much cells cost right now. I have built several Li powerd EVs and can purchase "standard" energy density cells for roughly 350USD/kWh. So my cost with absolutely no leverage and zero contracts in place would be approximately $16K for a 160 mile pack. (Given that we really don't know the exact capacity but can reason that it must be close to 50kWh.) I can only imagine how low TESLA is paying Panasonic with a four year contract for 160 million cells per year in hand. TESLA sure won't be telling anyone! ;-)

Don't forget two important points about battery cost. TESLA is in bussiness to make money and must charge us more than their cost. Obvious, but sometimes lost in these discussions.

Also, battery cost is not linear to capacity of the cell. I worked at an 18650 cell manufacturer a few years back and while all cells are created with the same care, there is a big range of outcomes. The last step before selling them is grading them by Ah. They are then sold by which bin of capacity they fall in with the highest capacity selling for an almost 50% price premium at the time. So the more capacity you want out of the same size volume, the dearer you pay.

My points are:

1) the battery degrades from three main causes.

A. Time. Est 90% capacity left at seven years.
B. Cycles. Est 80% capacity left after 500 cycles.
C. Over discharge or over charge. This degrades the battery faster.

2) a larger battery lasts longer.

3) the cost of batteries is decreasing while the capacity is increasing. The 300 mile pack should last over 15 years and 200,000 miles before dropping to a 160 mile pack equivalent.

4) the cost of the batteries is well below $20,000. This is the retail up charge for the entire pack, not it's "cost.". The used battery has a significant residual value.

5) people do not buy BMWs and Audis due to cost considerations, the Honda Fit would be cheap transportation choice. No one is buying the Tesla to save money.

6) the battery is not a cost to fill, but rather a capital cost. I would suggest that at 200,000 miles most ICE cars will need major engine repairs or will no longer be used for other reasons.

7) I plan to get a Sig (if I can afford it) and keep it for the rest of my life. The aluminum and electric motor should make the Tesla last far longer than other cars.

Looking into my Krystal ball, I think $20k would be a reasonable price for a 300 mile pack 10 years from now.

I'm thinking my pack will be down to 75% by then and that will more than meet my needs. I should be good for 20 years unless I can't renew the warranty and something bad happens.

Bringing this back to fill up cost.
My planned purchase is a 230 mile version.
I pay 7 cents in the winter in an all electric house in ohio and 12 cents in the summer. I never plan to drain the battery completely because that is when you damage cells, but if I had to the cost would be:
Winter = $.07 * 300/1000 * 230 = $4.83
Summer = $.12 * 300/1000 * 230 = $8.28

Ultimately, this all boils down to CHOICE.

I _choose_ to go BEV over ICE.

Someone else _chooses_ to go ICE over BEV.

All else is sophistory.

CD players used to be 1,000 buck. Now 20. Ten years ago your boss would laugh if you asked for an lcd. You can get a 25 inch one for 200 bucks. My phone has vastly more power than the mainframes I learned on 25 years ago. Technology marches on, and renewable energy keeps getting cheaper. And gas keeps going up.

Ten years from now when I swap batteries it might well be for a 600 mile pack for 15 k. I'd say get out the graph paper, and consider the effects of technology adoption and mass production.

And gas will keep going up I suspect....

"And gas will keep going up I suspect...."
unless we drive it down by not using it anymore.
Of course, that will take many years.

"And gas will keep going up I suspect."
I agree completely.

Last weekend, I was at a Nissan dealership talking with their Leaf salesman. I asked him "Suppose I roll into a Nissan dealership with a Tesla Model S, and ask to use the Level 2 charging station to refuel? (Assuming we have a J1772 adapter)". He said "No problem. All PEVs are welcome to recharge - for free".

Awesome. So, for at least some time to come, there will be many random opportunities for "free fuel" in public locations.

Q. Who's giving out free gasoline these days?? Gas stations won't even give you a free Slurpee after spending $65 to fill up.

David, your point is valid that there are currently free places to top off your charge. However, in the specific case, that was one salesman at one dealership. Nissan dealerships wouldn't be something I could count on in far flung districts.

Let's do a little math:

Suppose you drive 15,000 miles per year in a luxury car that gets 20 mpg (mixed driving). You're buying 750 gallons of gas per year. If the differential between gasoline and electricity is $3/gallon equivalent (i.e., electricity costs 25% of gas, at today's prices, and that differential holds constant dollar terms), then you're spending an extra $2,250/year on fuel.

Suppose you set up a little trust fund to pay for this gasoline habit of yours. Interest rates are low; 30-year Treasuries yield 3% currently. So, you'll have to put $75,000 in your trust fund today to buy your gasoline continuously through the future.

This same trust fund will also fund $20,000 on a new battery every 8 years (or that much money towards purchase of a replacement vehicle).

You will, however, enjoy the savings from the lower maintenance costs on your Model S compared to the complexities of an ICE car.


Ten years ago AA batteries cost me 50 cents a piece and today they are closer to $1. Ten years ago decent car battery was $100, today $150. Twenty years ago you could get a pretty good car for $15K to 20K, today it's closer to $50K (in some cases $60K and $80K.) As you can see, some prices go down, some prices go up. Although connected by the flow of electrons, the electrical power industry and the electronics industries are completely different beasts with completely different gestation periods. One deals in watts, kilowatts, and megawatts, and the other in bits, bytes, megabytes, gigabytes, and more. Moore's law for semiconductor devices has a time constant of one or two years while, if there were such a thing for power systems, its time constant would probably be in decades. Don't get me wrong, there have been great, if not spectacular, improvements in battery technology, but not remotely on the scale of electronics and information processing. In short, anticipating advances in battery and motor technology based on the model of electronics and information may be disappointing.

Ten years from now when you have, hopefully, owned your Model S for seven or eight years, you may not want to swap batteries. By then, if Tesla is as innovative and revolutionary as you believe, the Model SdotX may be so much more advanced that you may not be able to resist it and, instead, plop down $100K+ for the new one. What to do, what to do ;-)

Incidentally, I notice that Robrt.Boston's calculations, in a nearby post, seem to pretty much agree with my assertion that "fueling" costs, over an extended time, are comparable between a Model S and an ICE based vehicle. However, I don't necessarily accept some of his assumptions; I may address that separately.

The Nissan salesman I chatted with also indicated that in a couple of years, the Leaf will ship with an improved battery capable of a 160mi - 170 mi range. Price point will still be in the $30K to $40K range (before any tax incentives).

Meanwhile, over at the "SeekingOil", I mean "" website, the only technology advancements being discussed for ICE cars are "potential use of stop/start" to improve fuel economy by several mpg max.

FACT - Nobody will ever give me free gasoline.
FACT - I will never again be able to fill my gas tank for $12 or less. Not even close.

Spin the life-cycle numbers any way you like. At the end of the day 3 facts remain:
1. With a PEV I begin everyday with full range. Not possible with ICE.
2. PEV recharging from empty ($0 min - $12 max).
3. ICE refueling from empty ($45 min - $85 max).
4. The longer YOU hang around this site, the more likely YOU will buy a PEV. Yes, even you Zelaza.

Ok, that would be 4 facts :-)

There is a point about "fueling" cost in my model that I've forgotten to mention in earlier notes. While it is my contention that long term "fueling" costs between the Model S (including necessary replacement of batteries) and a conventional ICE are comparable, there is a significant difference. The price of gas goes, overwhelmingly, to the oil companies while the electrical fueling costs, as I consider them, go primarily to Tesla Motors and its suppliers. I consider that a good thing (Tesla getting most of the money rather than big oil.)

@zelaza, battery tech is now advancing faster than ever before. You see "steady" 8% drop in price every year, and current price is about $300/kWh. 90kWh = $27k -> $25k -> $23148 -> $21433 -> $19846 -> $18376 rounded $18k. That already is closer to 4000 than 40000, and that doesn't count any real advances that are around the corner. If DBM Kolibri battery is not an hoax this might already be order of magnitude too high.

Tesla is selling their Model S battery packs a bit high price. I bet there are big margins in those "upgrades", considering that actual batteries don't cost anywhere near that much.

Zelaza, compared to the Porsche Panamera, (unless Tesla falls on their face in the fit & finish department), the Model S is a bargain. Compared to the Audi A7, it's still a pretty good deal.

Compared to a Subaru station wagon, I'll admit it's a lot of fricking money and it's tough to justify it with fuel and maintenance savings alone.

That said, I think gas prices have nowhere to go but up, faster and faster. Our only long-term energy solution, IMHO, is solar. Solar cell technology is getting better and the price is only coming down in direct contrast to petrol prices. It won't be long before the lines intersect.

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