Tesla's battery marketing labels ("85kwh" etc.) aren't precise descriptions of pack capacity making this a bit trickier, for background here's a brief history of Tesla's batteries. Some time after the car went on sale 85 owners noted that their cars never showed anywhere near 85kwh used. This was explained by appealing to a 9kwh "brick protection" portion of the battery. Later wk057 showed (conclusively imo) that the "brick protection" consists of only 4kwh and the 85kwh pack only holds ~80.7kwh. A teardown (I think by wk057 again) of a 60 pack showed that 60's have 14 modules of 384 cells each. This showed the 60 pack was actually slightly under rated, its actual capacity being ~80.7kwh*[14*384]/[16*444] which is about 61kwh. The new 70kwh pack has 14 full 444 cell modules for ~80.7kwh*14/16 or about 71kwh, the 70kwh pack gets you 87.5% the range of an 85 and is a great deal imo. The 70kwh pack is closer to the 85 than the numbers 85 and 70 suggest because the 85 is actually closer to 80.7 and the 70 is actually closer to 71. The new 90kwh pack is 6% better than the 85 according to Tesla, and range numbers bear this out. But 6% better than 80.7kwh is only 85.5kwh... Which brings us to the new 75 and 100kwh packs. The 75kwh model X pack gets 17 more miles of range than the 70 putting it at about 76kwh. Given that the 90 pack is actually only 85.5kwh the difference in range between the 75 and 90 of only 20 miles makes sense if we assume the extra mass of the 90 costs it 2-3% in the efficiency department. But how is Tesla getting to 75kwh? and more interestingly, how are they getting to 100kwh? There are many possibilities, here are a few of the possible cases arranged sort of in order of simplicity. Case 1 A dramatic 15-20% increase in cell energy density has occurred, 100kwh is achieved by dropping the new cells into the existing 16 module packs. The 75kwh pack is achieved by using 12 full modules or by using 14 384 cell modules as the old 60 pack used to, probably the latter to keep the voltage up. This theory is attractive but I have doubts about such a large advancement in cell chemistry. Case 2 75kwh is achieved by taking the same 14 modules in the current 70kwh packand upgrading the cells to the latest chemistry. If the latest chemistry is about 2% better than what's in the 90kwh pack, which seems reasonable, this would get you the ~76 kwh required. But Case 2 has difficulty explaining the 100kwh pack, to get it we'd have to add 2 modules on top of the 2% advancement in chemistry, this would get us to about 98kwh. The problem with adding modules is it would increase pack voltage or require a redesign of each module to keep pack voltage the same. Increasing pack voltage would almost certainly require a redesign of the motor controller, and possibly a motor redesign. Also adding modules means the pack probably cannot be retro-fitted to existing cars. Its also possible that they just take an 87kwh (85.5kwh plus 2%) pack and call it a 100, but that would be disappointing... Case 3 Cell geometry change in 1 dimension. If there's a cell geometry change in one dimension it will probably be to lengthen the cell, Tesla is constrained by the height of their modules and a .4 inch increase in module height would correspond to a ~15% increase in pack capacity, which sounds worth it to me. Additionally, lengthening cells would allow for minimal changes in cell and pack assembly equipment while also minimizing the decrease in gravimetric energy density that accompanies increasing cell size. The 75kwh pack would be achieved by using 12 full modules or by using 14 384 cell modules as the old 60 pack used to, probably the latter to keep the voltage up. It's likely that this pack would not be retro-fittable to older vehicles but it's *possible* that it would be. Some benefits of this scenario would be that increased power and charge speed would be more or less guaranteed, which wouldn't be the case for a pure chemistry improvement scenario. Case 4 Cell geometry change in 2 dimension (or 3 dimensions if you want to use cartesian coordinates on a cylinder). If the cells change in length and radius it would be difficult to anticipate what might happen, 18750s would be the obvious candidate for Case 3 but in Case 4 here it could be 20700s or 20750s or 22700s or numerous other combinations of height and radius. For this reason i won't even try to speculate as to how it might play out. Case 4 is possible but I think it's the most unlikely of the possibilities at this time due to the number of engineering changes it would require. Right now I'm leaning towards 1 and 3 as the most likely cases but my level of confidence is not high. Cast a vote, the collective wisdom of TMC has been correct before. Also if the new 100 pack is a true 100kwh pack, the Model S 100D should have a range of about 340 miles, and the Model X 100D about 300.