The 85kWh battery looks like a flat tray and is fitted to the skateboard. Would it be possible to fit 2 flat trays instead of 1?

The 85kWh battery looks like a flat tray and is fitted to the skateboard. Would it be possible to fit 2 flat trays instead of 1?

The hight of the car will be more offcourse. And the car will get heavier. But you will have doubled the amount of electricity that can be stored in 1 charge. The range will also be much more. The range will not be doubled, but it will be significantly more. Maybe 80% more range. Is that possible?

Superliner | 1 februari 2013

Can you say, Model X 2.0 !!

Brian H | 1 februari 2013

Passengers' knees would be up around their chins.

Joshua Burstyn | 1 februari 2013

Actually Benz, I calculated the following:

40Kw: ~160 mile range.
60Kw: ~230 mile range.
85Kw: ~300 mile range.

how many Kw per mile:

40 Kw for 160 miles is 0.25Kw/mile
60 Kw for 230 miles is 0.26Kw/mile
85 Kw for 300 miles is 0.28Kw/mile

Theoretically a 170Kw pack would then get you 600 miles, assuming weight and drag scaled linearly using the 85Kw KW/mile stat. Then we take into account the falling efficiency seen above... note the rise from 0.25Kw/mile to 0.28Kw/mile ratio. It seems small here but in the end I suspect you'd seemingly get about a 12% loss in efficient by doubling the pack(s).

If any of my calculations are right, that means a 170Kw pack would achieve about 528 miles. In practice though it'd probably be much less efficient than that due to additional drag, the additional strain in climbing hills (weight penalty) and so forth.

It's good to think of these things though and I enjoyed doing the calculations. (Even if I'm way off!)

JZ13 | 1 februari 2013

And what would the additional price be? $20k?

ghillair | 1 februari 2013

@JZ more like $35 to $40k.
It is $20k to go from 40kw to 85kw on the MS.

Benz | 2 februari 2013


The shape of the car will have to be changed. The floor of the car will be about 8 inches higher from the ground. In order to have enough space for the passengers in the car, the roof of the car shall have to be 8 inches higher from the ground as well. That would not be a too difficult job for Franz von Holzhausen, I think.

If the range of the car would increase by 200 miles, the total range would become 500 miles!!!!

Let's not worry about the price yet. The main question is: "Is it technologically possible or not?"

Brian H | 2 februari 2013

8 inches! Not a chance. Not going to happen.

teddyg | 2 februari 2013

Almost anything is possible if you are willing to ignore the costs of production.
I used to think that EV's had to have a range of 500 miles before the masses would ever embrace them. However the added weight and costs associated with this will make them unaffordable and reduce performance. While battery tech may evolve to allow for 175+kWh in a car eventually, that battery tech is unlikely to be inexpensive for many vastly improved technology is rarely cheaper than old in the battery business. Tesla is trying to bring the price of EV's down...not drive them higher.

My view changed when Tesla unveiled the Superchargers. You just have to realize how rare trips of over 200 miles in one day really are.
With superchargers in place every 150 miles I feel like a real world range of 250 miles will be the ideal range settled at for future EV's...this will allow for capacity degradation so that even after 10 years of average driving you should still be able to make long distance trips by making it to the next supercharger on your journey.
The supercharger network will mean battery capacities really don't need to go much higher than 75 kWh which will help to keep costs down as technology improves and cars/batteries get lighter.

I think Tesla could still provide an option for people who wanted more range and a bigger battery but to set a goal of a 500 mile range for every car they produce would be a huge waste of resources and ultimately make their cars unaffordable.

Brian H | 2 februari 2013

I think tech will eventually make 500mi cars affordable, but you're right, the existing batteries plus SC n/w is a good "holding pattern".

Benz | 2 februari 2013

Before 2008 there were no EV's in the market available that had a real long range. In 2008 the people had the option to buy the Tesla Roadster. So, suddenly there was a way to drive longer distances then you normally could have with an EV. Elon Musk: "First you have to show the people that there is a way, then there will be plenty of will". The fact that the Tesla Model S is such a great success shows that Elon Musk is right. If you can make something happen that actually was considered as "not possible", then you can change the reality of today, then you can make people walk into a different direction then these people normally would have chosen to walk. Since the success of the Tesla Model S, the idea of buying a EV instead of a ICE vehicle seems to be "not such a bad idea" at all. People are now considering the Tesla Model S as a really good option actually. Just because there wasn't one available before.

Elon Musk also says that nothing is impossible. And everything the people of Tesla Motors do, they do it for their customers.

I really do believe that someday (before 2025) there will be EV's on the market that will have 2 flat trays of battery packs in the floor of the EV (like I have mentioned in my first post of this thread). And the battery packs of the future will have more capacity. Then we shall have EV's that will have a range of much more than 800 miles on a single charge. Just imagine this in combination with the fact that there will be a network of Superchargers. The future of EV's is bright. Fasten your seatbelt, and enjoy the ride.

Brian H | 3 februari 2013

Benz, sometimes you sound like a teenager; double-thick trays? There will be capacity increase, but that silly idea is never going to happen.

Benz | 3 februari 2013

I sure would like to be a teenager again. Those were the days ........

I am progressive and positive minded, I like to think about what is possible and what can be achieved, I like change/development for the better, I like to see things improving, I like to go forward, I like to accelerate instead of holding back, and while driving I try not to use the breaks very often (only when I really have to). Please excuse me for being like that.

In this world we need both progressive and conservative minded people. I respect everyone. That's what keeps us in balance. And I am just doing my share.

teddyg | 3 februari 2013

No offence Benz but there will never be an 800 mile range EV, just as there will never be a 500 gallon gas tank in a petrol powered car.
Why? Because with gas stations everywhere there is simply no need for it..if anybody ever filled up that tank it would weigh so much that it would slow down the car dramatically and cause it to run very inefficiently...this is the same for a 200+kWh would weigh so much it would make the car very slow and inefficient...with superchargers every 150 miles apart there is no need to weigh down the car unnecessarily as this will only cause it to use more energy for every mile travelled.
As I say a 250 mile range is more provides more than enough range to cover people's average daily needs (less than 50 miles per day for 95% of people) and with superchargers every 150 miles you are also easily covered for long distance.
Maybe one day we will be able to store 200kWh in a soda can but it is not likely to happen in my lifetime...till then we have to be practical in getting costs down far enough so that the average person can afford to put an EV in their garage.
Once the average person realizes that the EV is the only way forward then we can start to dream a bit more...but right now the EV revolution is in its infancy...we have to walk before we can run.

Benz | 3 februari 2013

Allright, the weigh of the EV will become too much, maybe I should be more realistic about the technology of today.

I shall put this idea in a folder, and I will look it up again in 2020. How about that?

Joshua Burstyn | 3 februari 2013

Benz, don't let people discourage you. They're right that a double load of batteries probably isn't practical right now but ignore the noise and keep dreaming.

olanmills | 3 februari 2013

There is no need to double the thickness of the floor to increase the battery size.

This might seem obvious when I say it, but only reason you would consider doubling the thickness of the battery pack is if you couldn't fit all of the desired battery capacity in the current 4 inch floor.

However, the reason that the Model S tops out at "only" 85kwh is not because that's the most batteries they could stuff into a 4" case. It's because of cost and practicality. In truth, they maybe could pack more batteries into the floor (don't know for sure since battery pack design is a secret), and/or they could definitely use batteries with a higher energy density.

There is cost to consider though. Tesla wanted to produce a Sedan that they could sell for $50 - 100k and make a profit doing it. A 600 mile or even 1000 mile EV range is technically possible today, but it also has to be practical for Tesla's business goals as well.

negarholger | 3 februari 2013

Olanmills - over on the TMC site there is an inside look of the battery. Cells are spaced intentionally fairly wide apart for crash protection and thermal separation. Traditional batteries are large cells arranged in series - if one cell fails the whole battery fails. Teslabattery is like a web of small batteries - if one cell fails the whole battery still works, just a little less capacity. Every single cell is monitored for current, voltage, temperaure and indivudually balanced and fused for over current and cell pressure.

Benz | 4 februari 2013

@ Jewsh
Dreaming is like having fun, as in dreams nothing is impossible.

@ olanmills & Kleist
Reality is what we have to deal with. So, it's important to keep our feet on the ground. And it's good to have some people around you who help you with keeping your feet on the ground. Communication is vital.

So, I understand that it actually is possible (to have more kWh in a battery pack), but there is more to it to make it more successful in our real world. Good to know that. Thanks.

teddyg | 4 februari 2013

By all means dream away...i have always said Tesla could offer bigger batteries to those who want to buy them as an option.
I just feel that once the supercharger network is up, people really start understanding how EV's work, and their real driving patterns most will come to the conclusion that:

1. They don't travel more than 200 miles in one day very often (maybe 5% of the time)
2. They can hop from suercharger to supercharger every 150 miles until they reach their long distance destination (about every 2.5 hrs of driving for a 30 min supercharge to top off)
3. Batteries are very expensive so it is in your interest to purchase the battery size that suits your needs best.

From this I feel that most will opt for the smallest battery that allows them to hop from supercharger to supercharger when they take rare long distance trips.

This is why I think Tesla is going to produce the base model Gen III as a car with a range of 200 miles (real world) and supercharging capability. It will sell for $32,500 (after govt incentives). Oh yeah and 0-60mph in 5.5 secs too!

People can choose bigger batteries as an option but as I said I think when most start to understand all of the above they will see that for the vast majority a 200 mile real world range with supercharging ability will work for most. This is how we get to an affordable EV capable of long distance travel...for now anyway.

Benz | 4 februari 2013

@ teddyg
Your view sounds realistic to me. And yes, before making their final choise, they will count their money and deside what they can afford and want to pay, then they will choose the right capacity of the battery pack which will suit them best.

negarholger | 4 februari 2013

Benz - I agree with you a car in the Model S class should have an EPA range between 400 and 600 miles. However we are just at the very beginning.
Dave Duff from TM had a seminar at Stanford (search youtube for Dave Duff)... explaining the TM thinking - in short a vehicle retail price is 60% body and 40% drive train. So if a 265 m EPA battery costs $40k today then the car should retail for $100k. A 500 m EPA battery costs today $80k and so the car should retail for $200k - unfortunately a much smaller market.
Bolting another battery under the S adds about 1000 lbs and that decreases the efficiency (roll resistance, mass to accelerate and deaccelerate, etc). But TM thinking is "do more with less"... (that is the one thing I like most about TM).
Here is my vision for Model S V2.0 in 3-5 years
- same battery pack but use 4Ah cells (+160 lbs) = 110kWh
- reduce body weight by at least 160 lbs
- reduce roll resistance (tires)
- improve drag
- more efficient high current battery charge/discharge using e.g. a small capacitor buffer to level current peaks
- tweak engine efficiency ( tighter tolerances )
- more efficient inverter
If above improves the W/m by only 15% and with the 110kWh battery then you would get about 440 miles EPA.
Most of the above you will see first on a Gen3 car - here 60kWh at 230W/m will get 265 m EPA range which is perfect for the Gen3 car.
One thing I have realized listening to Elon and TM that they are thinking 2-3 plays ahead of everybody else. A Gen3 car would charge at every SC, while the Model S V2.0 would stop at ever second... with planned 120kW SC you would add more then 220m EPA in 30min.

teddyg | 4 februari 2013

You fail to mention the cost of your 110 kWh pack Kleist.
New battery technology is rarely cheaper than old (in fact it never has been)...I think Tesla is building out the supercharging network for the precise reason that 95% of people travel less than 50 miles per day. It is even more rare that you will travel more than 200 miles in one day! So why would you put in an insanely oversized battery pack that will cost a fortune, slow the car down, and decrease its efficiency due to the weight of all those batteries..all to cater for a trip of 440 miles non-stop which you MIGHT do a few times in your entire life!

Think about it...even if you wanted to drive 440 miles in one sitting (nearly 8 hours of non-stop driving)...would you really do this? will stop once every three hours or so to use the bathroom, get a drink/snack, and stretch your legs. Well this is the average for most normal people anyway. This usually takes about 20-30mins and so is a perfect time to supercharge.

In this way yes Tesla can use the 4.0Ah cells but as Gen III will be lighter, more efficient, and have less drag...they will be able to use LESS cells to get the required 75 kWh they will need for a 200 mile supercharging capable Gen III.

This is how you get to an affordable EV for everyone...not by stuffing in 110 kWh of batteries and making the car less efficient and more expensive..but by reducing the battery size and weight thereby increasing its efficiency (while still maintaining enough range to allow for hopping between superchargers for rare long distance trips) and therefore lowering the price.

Benz | 5 februari 2013

@ Kleist & teddyg

I think that you both do have a point. There are two different things to think about:
- What is technologically possible to manufacture?
- What is really going to be affordable for the grand majority of the Tesla EV buyers?

There simply are always people who want to have the best of the best, and most of the time these people have enough resources to pay for what they want. These people cannot be satisfied with the second best thing, no they are only interested in the best what is available at that moment in time. For these people, the Tesla Model S V2.0 will do just fine, even if they will have to pay 200k for this EV. What I am saying is that there is a market for every EV.

And secondly, for the grand majority of the Tesla EV buyers, teddyg has already explained why a more efficient EV would be better: the price.

Vawlkus | 5 februari 2013

Keep in mind Elon has already stated that a 500 mile pack is possible, but not economically feasable.

negarholger | 5 februari 2013

teddyg - agree with all what you said. However I was looking at it from a slightly different angle.

- I used the example of an 2018 Model S V.0 that retails for ~ $125k with largest battery ( 5% price increase annually and some added puff-puffs)
- battery cost for 110KWh is the same or lower - it uses same number of cells as todays MS, bulk cell cost should not be higher. However cells are slightly heavier. But reduce the number of cells to get 100kWh end you end up about the same weight.
- if new battery technology ( or any other technology ) is not cheaper, then there is no reason for new technology. Yes, new technology will always retail for a premium, because you are willing to pay for it not because it costs more. (we make the fat profits in the first 3-9 month of a new product, afterwards it fills the factory for a fair profit)
- 4Ah Panasonic cell was announced in 2009, start production 2013. In case TM should select it for Gen3 in 2015 then it is a mature product(one advantage of using lap top batteries)
- totally agree 265 EPA is in line with my driving habits and I would stop at Harris Ranch and Tejon anyway going to LA.
- a luxury MS V2.0 with ~400 miles EPA would add the convenience of not to have to stop at Harris Ranch... convenience is what people are willing to pay for extra.

My whole point was not to balloon the battery, but the key is to improve EV efficiency.

The traditional car industry is struggling to improve efficiency and caught overstating ( Kia, Ford,...) If the ICE had 75% thermal efficiency then the EV would pretty pointless today.

teddyg | 5 februari 2013

I think the max range you would ever want in an EV really comes down to how long someone could physically sit in and drive a car non-stop, comfortably, without eating/drinking, or using the bathroom.
I would say this would be about 4-5 hours max (sure many could go longer, but would they be comfortable?)
So lets say 4.5 hrs at 55 mph (average) = 247.5 miles travelled.

This is why I think that a real world driving range of 250 miles will be the standard issue for the EV (any bigger batteries could be bought at an optional extra cost).

Basically it comes down to human nature and our needs after a certain amount of driving and sitting in one position. We need to eat/drink, use the bathroom and strech our legs after a certain amount of time in one small confined area.
It seems to me that these human needs after 4.5 hrs of driving need to be met, providing an ideal opportunity to stop and supercharge for about 30 mins.

The Model S 85 kWh car is already there, which is why I think a lighter, smaller, more aerodynamic Gen III should be able to get 250 miles from a 60-65 kWh pack...

60 x $212.50 per kWh (in 2016) = $12,750...if battery is 40% of total car production cost as has been claimed then total production cost would be $31,875 add in 25% profit = $39,843 minus $7,500 tax credit gives a final price of roughly $32,500 to the consumer for a real world 250 mile range Gen III with supercharging capability.

teddyg | 5 februari 2013

I also think that even if the ICE were able to match EV efficiency the EV is still the superior vehicle due to its packaging as seen in the Model S and other benefits.

1. Flat floor battery pack puts bulk of weight at lowest center of gravity providing exceptional handling and stability (not to mention reducing rollover risk which will be a big selling point for Model X when up against other top heavy ICE powered SUV's). The ICE generally sits above the front two wheels in a vehicle, the heavy momentum when accelerating and stopping throws this ICE backwards and forwards causing the car to lurch backwards and forwards throwing off the balance.

2. Electric motor in between rear wheels...again low centre of gravity benefits. But also allows for "frunk" storage space. Because no gas tank the rear trunk can be bigger as well. Not only does this provide for best in class storage space but also best in class safety as crumple zones are much larger than any ICE vehicle.

3. No exhaust, clutch, gears, sparkplugs, etc, etc...all things that can go wrong...average ICE car has hundreds of moving parts...the EV has just a handful. No exhaust allows for a clean flat underbelly which aids aerodynamics.

4. Electricity can be produced with zero ICE can never claim to be emission free. Also we can much more easily filter emissions from a few hundred remotely located stationary power plants than a few hundred million mobile ICE powered vehicles operating in and polluting our most densely populated areas.

5. Superior traction control (when AWD version is released)...the electric motor will be able to react much more quickly to slippage input from the wheels. An ICE has to wait for gas to be fed, pistons to fire, etc, etc, before it can react to input from the wheels. The AWD EV will result in revolutionary handling the likes of which the world has never seen. This is also a safety issue as the faster you can avoid a crash the safer you are.

6. Electricity is always produced domestically providing for domestic jobs and supporting the domestic economy. We cannot say the same for oil/petroleum/diesel, etc. We don't have to transport electricity halfway around the world. We don't fight wars over electricity supply. We don't have electricity spills that destroy the environment costing billions to clean up. Only 5% of the world's electricity generation comes from oil but 70% of oil use is for fuels to power the transportation industry. Think about that when considering how much the oil industry fears the EV.
Coal provides about 40% of the world's electricity but is on the decline in nearly every nation (yes even in China and India as a % of the grid). See how SolarCity and Tesla will be collaborating to get the world on the path to true zero emission living.

Anyway these are just a few of the benefits...but this is long enough for now methinks

Benz | 6 februari 2013

@ Vawlkus & Kleist & teddyg

"Keep in mind Elon has already stated that a 500 mile pack is possible, but not economically feasable."

The whole issue in just one sentence. How about that?

Joshua Burstyn | 6 februari 2013

Up until the Model S battery capacity was the biggest issue. Many users (myself included) needed to be sure their daily commute and many of their longer pleasure trips were possible in a single charge.

Given that many high performance cars have a range similar to the current 85Kw Model S the stumbling block now becomes charge times. (For the purposes of discussion we will assume fast and slow charging of the batteries allow for the same level of battery longevity.) The superchargers are a great first step. Hopefully as time goes on we will come up with some options for even quicker charging though.

Remember; most drivers don't care what fuel their car takes. For these same drivers it is all about how fast they can get in and out of the gas station for the least cost.

Brian H | 6 februari 2013

The real key to EV fuelling is avoiding stations (gas or other) altogether. Home charging, "full every morning", is what most users do and love.

Joshua Burstyn | 6 februari 2013

I'd agree with you, Brian but again longer trips would clearly require charging outside of the home. A user on a long trip would want the comfort level associated with the ability to quickly (<30 mins perhaps) recharge from anywhere.

Superliner | 6 februari 2013


I envision a 500 or more mile range capable BEV. I read some time ago about a company that was experimenting in making batteries in different shapes. In theory with inert battery chemistry one could construct the car structure itself out of live cells.

The S weighs approx 4700 lbs. including approx. a 1600 lb. battery pack. Suppose their research came to fruition? While overall weight remains @ 4700 lbs. if the chassis and stressed members themselves could provide energy storage one could theoretically construct a 4700 lb. car where 3000 lbs. or more? was energy storage. The car itself becomes the battery. as opposed to building a car and placing a battery in it.

Since the overall weight remains constant the performance would not suffer in fact it should improve as far as acceleration. Handling might suffer due to a higher CG

The T-Zero used a rather innovative approach to battery placement although the car itself was not very practical but the Roadster was only marginally better mostly by adding creature comforts.

Nobody thought there would be a car such as the Model S either as recently as 10 years ago. All the heavy hitters said it could not be done. Good thing Elon did not listen to them.

As always the people who say something cannot be done are in the way of those who are doing it!

Superliner | 6 februari 2013

These batteries..

can be made in any shape. tomorrows technology is being built. As my hero Mr. Spock was fond of saying "I'd like to think there are always possibilities"

Timo | 6 februari 2013


I think your estimate about battery weight is a bit high. 8000 (~89kWh) * 46g (each) gives only 368kg which is about 811 lbs. I don't think pack structure, wires & cooling quite double that weight even with bottom armor that probably is a bit thicker than ordinary cars have.

Also doubling the battery amount would not require that bottom armor being any thicker, so that doesn't count in adding more batteries.

negarholger | 6 februari 2013

The Model S battery assembly is 0.16 kWh per kg

Timo | 7 februari 2013

That gives 531kg for 85kWh pack. 1170 lbs.

Timo | 7 februari 2013

BTW, Kleist, where did you get that info?

negarholger | 7 februari 2013

Dave Duff - Stanford Seminar video.

Benz | 9 februari 2013

Suppose that Tesla one day would manufacture an all electric Bus which has at least 60 seats for the passengers. Now, that is a vehicle that has a lot of room in the floor, because the giant size of the floor itself, and because all the seats are pretty high from the ground. So, there will be lots of space to store a whole lot of (18650) batteries. How about that?

Tiebreaker | 9 februari 2013

Where is that bus going?

Benz | 12 februari 2013

The hight of the battery pack (which is now used for the Tesla Model S) is only 4 inches!!! I thought it was 8 inches high. So, the hight shouldn't be a real problem (2x4=8). But the extra weight of the second battery pack will make the EV too heavy. So, the weight is actually the real problem. Maybe this idea can be used when battery packs get lighter (2030?).

mattmorgret | 12 februari 2013

If Tesla is already offering to let you pre-pay for a 85kWh batt 8 years from now for $12k, its probable that a 170kWh battery will be available for about the same price as an 85kWh battery costs today, roughly $30k.

Using a linear 10.5% discount on the price of batts, if we assume an 85kWh batt costs 30k today, in 8 years it will cost $12.35k for the same batt (new), so that is what Tesla is predicting, about 10.5% reduction in price per kWh per year going forward.

Seeing that most car manufacturers run a model for life of 6-8 years before changing the model design drastically, a Model S 2.0 could easily see a 500+ mile range imho.

mattmorgret | 12 februari 2013

You guys that are saying the 170kWh battery will weigh twice as much or ride twice as high are using today's speced batts, not the batts of 8 years from now. The energy density will double, but the weight will stay about the same or maybe even be lighter. Panasonic has increased the 18650 from 2200mAh (45.9g) to 3100mAh (45.7g), and increase of 40% in energy while also gaining .2g in net weight.

I have also seen 3400mAh batts are starting to trickle out and they also weigh about the same.

Benz | 13 februari 2013

@ mattmorgret

OK. Improvement of technology is always good.

Brian H | 13 februari 2013

Yes, improved energy density MEANS more electrons per gm. There's a long way to go before such improvement is at an end.

Benz | 14 februari 2013

One day it will be reality.

Maybe in 2030?

Timo | 14 februari 2013

Twice the 3.1 with approx 8% annual increase:

2013 3.1
2014 3.348
2015 3.61584
2016 3.9051072
2017 4.217515776
2018 4.55491703808
2019 4.9193104011264
2020 5.312855233216512
2021 5.737883651873833
2022 6.19691434402374

Only 10 years. Also rate probably is faster than 8%, that's quite conservative approximation considering that Si-based Li-ion batteries are at their infancy and at beginning of the tech development speed is usually highest.

Benz | 14 februari 2013

@ Timo

That is sooner than I expected. Maybe 2020 is more likely then. And that is not really that far in the future. In my opinion 2020 is near future.

rohit123 | 15 maart 2013

Great content

Bubba2000 | 16 maart 2013

Timo - Informative table and the magic of compounding. Per your table the equivalent to MS85 could be MS125 with the same number of batteries and at lower price. 440 nominal miles. The car could loose some weight using stronger Al alloys, improved structural design. 10% of weight could mean 6% increase in range. Increased/improved inverter +motor efficiency regeneration, electronics, insulation, etc could add another 5% to range. Even aerodynamics could be improved. Potential to increase nominal range to near 500 miles in 5 years. That would enable to car to address the hi end market and mitigate range anxiety.

Meanwhile, Tesla has to increase the coverage of chargers. I think the 100Amp/240V chargers makes the most sense in cities. hotels, restaurants, etc. They are relatively cheap. If the power is available, it may cost may be $1,000 per hook-up in a places like hotel parking lots or even MacDonald. Most hotels, restaurants got industrial hi capacity, 3 phase hook-up to feed the kitchen, HVAC, etc. Even it the company spends $20,000 per site, that is 50 sites/$1,000,000. Spend $10M that is good for 500 sites, or 10 charging locations in each state, each with 10-20 charging hook-ups. $10M is what a decent shack costs in San Francisco. The hotel or restaurant could charge for electricity and would benefit from the hi end clientele, free advertising by Tesla.