40 or 85 kwh

40 or 85 kwh

I'm looking at a new job that would require 130 miles of driving per day. This would use up the 100,000 battery warantee within a few years. I'm trying to decide if it is worth getter the 85 kwh battery and get unlimited mileage in the 8 years, or just go with the smaller 40 kwh battery, assuming that they will need to be replaced. Does anyone have any clue what the replacement cost is?

Sudre_ | 23 oktober 2012

The 85kwh battery is the only way to go in my opinion with that mileage.

Bperry01 | 23 oktober 2012

Certainly a personal choice, but one thing to consider, is 130 the max you'll be driving? 160 is the quoted max of the 45kwh battery. And with so many possible energy draining variations on your day, AC, high speeds, hills... etc. You might not be able to count on 130 of that 160 every trip.

I agree that 85kwh is your best bet. Not only for warranty max but just daily range limits.

Docrob | 23 oktober 2012

The deeper you cycle the battery the quicker battery degradation will occur, with the 40kwh battery you will be doing a daily. 80-90% discharge, with the 85 Kwh battery it will be more like a daily 50% discharge, better lifespan and more flexibility if you get home then have to make an unexpected drive somewhere if you have the 85kwh model.

GoTeslaChicago | 23 oktober 2012

you should be choosing between the 60 kWh and the 85 kWh. The 40 kwh is inadequate for your usage.

That said, the 85 kwh with supercharger is the best deal.

mrspaghetti | 23 oktober 2012

@GoTeslaChicago +1

jbunn | 23 oktober 2012

I had a smaller commute when I reserved. 70 miles RT acutaly. I wanted two trips in case I forgot to charge (140), plus battery degradition over many years, plus extra range to run errands. That led me to select the 60.

Today the price difference between the 60 and the 85 with supercharger is only 8K. I was one of the folks that were early 60 supercharger adopters, but if not, I would go for the 85. Especialy with your long commute, nearly double mine.

ChasF | 23 oktober 2012

I'm getting the 40kw pack myself and even I think you should go with the 85 kw.

Longhorn92 | 23 oktober 2012

I too am getting the 40 kWh battery like ChasF, but with your kind of mileage, I would highly suggest you go with the 60 or 85 kWh battery pack. I'm not as concerned on the warranty side, but 130 miles could eventually be really stretching the 40 kWh battery based on degradation as well as driving conditions. In fact, it may be stretching it from the beginning simply by using a standard charge, and I don't think you want to be range-charging every day. Also, in a few years when the battery is 90% of what it was new, you might be going to work on a really cold day, so you will be using the heater to a great extent, maybe going 70 mph, have a few high speed passes as well, and 130 miles is just not possible. Regardless of the cost in a few years, I don't think you will want to replace the battery for at least 8-10 years.

Timo | 23 oktober 2012

I think you need at least 60kWh version. 75% of 40kWh 160 miles after battery degradation is only 120 miles. With that amount of driving you will get the mileage that hits that number pretty fast.

I would personally get the 85kWh version. Less fuss about recharging and less battery degradation, more power and so on and so on.

Volker.Berlin | 24 oktober 2012

Nobody has any clue regarding availability, capacity, or cost of replacement batteries ten years down the road. That's a reality you just have to face. Even Elon is guessing, and based on his view of the development, the cost per kWh is falling by at least 8% (if I remember correctly) p.a.. That amounts to quite significantly improved range *and* much lower price in ten years' time! But even this doesn't really help to estimate the cost of a replacement battery in the future, because we don't know the cost of the battery pack in the Model S today to start with.

With a 130 mile commute, IMO the 85 kWh battery is a no-brainer. Not just because of the unlimited mileage warranty, but also because of it.

If you're still unsure, these threads may help you decide:

Mark K | 24 oktober 2012

Technology inevitably gets cheaper and better.

Buy no more than what you need for today, but never less.

At 140 miles / day, you need a bigger pack. The 40 won't do it.

My commute is 4 miles / day ... and I'm getting the P85.

My need? Fun!

ColonyGolfer | 24 oktober 2012

One key question has not been asked of mhargreaves......Is your new job as a travelling salesman, or sre you commuting 65 miles one way? If you can recharge 8 hours at work, you probably will not need the 85KWh. Also, where do you live? My car is in FL, and the max projection of range on my car is 180 miles with the "standard" charge in an 85Kwh battery. This is based on my having the AC running when I drive.

Volker.Berlin | 24 oktober 2012

Technology inevitably gets cheaper and better. (Mark K)


Buy no more than what you need for today, but never less. (Mark K)

I agree with the premiss but I draw a different conclusion:

To me, it is a similar decision as with RAM or processor when buying a new computer. You know in advance that no matter how much you spend, your system will be worth next to nothing after very few years. And just a few months later, you may be able to get a better system for the same money, or get the same system cheaper. That's the way it is, but when I look at the past, the only times when I was dissatisfied with my choice were when I had spent too little. I have never felt remorse for having opted for the upscale, more expensive, more depreciating choice. I am much more satisfied with a good if I know for sure it was the best I could get/afford at the time. Otherwise, I will constantly suffer from perceived low performance, it will nag me whenever I use the thing, thinking if only I had not been so greedy in the first place. Then I will try to upgrade sooner than I would have otherwise, and I will end up at the same cost or even more expensive. (myself)

Vawlkus | 24 oktober 2012

85 all the way

jerry3 | 3 november 2012

I agree with Volker "when I look at the past, the only times when I was dissatisfied with my choice were when I had spent too little."

Get the biggest system (or battery) you can afford because it will be:

a) more fun when you first have it, and

b) the time when you are forced to replace it will be longer. My SGI Octane lasted for ten years and it was still faster than the system that replaced it in some respects (Regrettably, SGI's management ran the company into the ground). The 85 kWh battery Model S will be the same.

Of course, you can always wait X years and things will be faster and cheaper but at that time you can wait another X years and they will be faster and cheaper again. There is no end to that cycle. Your best shot is to get the 85 kWh battery Model S (or computer, or audio system, etc.) and then never read another review until you are ready to retire the current one.

ChasF | 3 november 2012

+1 @jerry3

Volker.Berlin | 3 november 2012

(Regrettably, SGI's management ran the company into the ground). The 85 kWh battery Model S will be the same. (jerry3)

I disagree. Elon won't run Tesla into the ground! :-P SCNR

jerry3 | 3 november 2012


The lack of an editing function got me again :-)

Brian H | 3 november 2012

The S and 85s were made for each other. The other batteries are compromises which broaden the market somewhat. (TM's lowest cap battery is bigger than the largest competition!)

robert27 | 3 november 2012

The 85kw motor is awesome. If you are really going down this road, do not underpower yourself. It is worth every penny!

Brian H | 4 november 2012

The motor is the same. It's the battery that's different ...

nickjhowe | 4 november 2012

@Brian H is correct. To add a bit more detail: the Performance 85 motor is different. All three standard models have the same motor. The lower acceleration of each successively smaller battery is (probably) due to different (computer-controlled) limits on the current that can be pulled.

DouglasR | 4 november 2012

Also, the battery is rated by energy (kWh), not power (kW). The motor has maximum power of 270kW for Standard, or 310kW for Performance.

Does anyone know what voltage it operates at?

BYT | 4 november 2012

What does that mean if a 310kWh battery is offered in the future for a P85 purchased today?

DouglasR | 4 november 2012

If the battery can be swapped in, it means the car will have a range of almost 1,000 miles.

But maybe you misunderstood my post. I said the Performance motor (not battery) develops 310 kW (not kWh) of power (not energy).

BYT | 4 november 2012

Yes, in my excitement DR I read what I wanted to read... :)

nickjhowe | 4 november 2012

@DouglasR - I've seen c. 420V mentioned in the forums.

Jolinar | 4 november 2012

It is personal choise, but 40kWh is too small for you... What if you'll have AC on all the time and there will be something unexpected on the end of your trip (some detour for example), your range anxiety will drive you crazy :)
I think you should schoose between 60kWh and 85kWh (and consider that 85kWh has supercharging included).

jkirkebo | 5 november 2012

Battery voltage is around 365V nominal. Over at one of the supercharging-treads, someone reported a starting voltage of 358V when charging from ~22% SOC and an end voltage of 396V when full (after 65 minutes).

David M. | 5 november 2012

I would go with the 85kWh battery even if you had to sacrifice some of the other options.

HenryT2 | 14 november 2012

I was planning on buying the 40kW. After the test drive, I want the performance model! I can't really justify it though. I'm retired. Car will mostly be used for grocery shopping, etc. It's a rare occasion when we drive 70 miles round trip (mostly 20-30 miles a day).

Just curious as to the demand of the various versions and whether my resale value would suffer. Not really planning on selling any time soon. But it's nice to know that you have some resale value in your car.

Any opinions?

Jamon | 14 november 2012

@HenryT2: I had the same concern about wanting a performance model, so I specifically asked to test drive a non-performance car. It was an incredible drive! I'm sure you'll be perfectly happy with the non-performance car, and so will your future buyer (if you ever have the heart to actually let this car go!). I was originally planning for the 40kW, but decided on 60kW so I could use the superchargers and make longer distance road trips if we ever want to.

DouglasR | 14 november 2012


Like you, I am retired and don't drive a lot. Still, the performance model was awesome. I could not justify it, but then I decided, at my age, I don't have to.

Brian H | 14 november 2012

I think the P is turning out to be the highest volume choice, despite expectations that the 'median' 60 would be.

clearly you'll have to locate some more distant grocery stores!

Just try to live up to your end of the Lord's Prayer line, "Lead us not into temptation." Not that the P85 is evil ... is it?

Beaker | 14 november 2012

@ Brian:
"Lead us not into temptation.
But deliver us our model S"

DouglasR | 14 november 2012


I've heard of car of the year and man of the year, but this is getting ridiculous.

Brian H | 14 november 2012

First there was the Golden Calf. Then, 3,000 years later, there was the Model S. At first, the people were delighted ...