We contacted Jerome Guillen VP, W W Sales & Service yesterday regarding the loss of range on our and many others' Model S and what the solution was. To our pleasant surprise we received a prompt reply from him today which should allay everyone's concerns regarding this issue which has generated several threads on this and the other forum. We decided to post his reply on the forum to help ease everyone's worries and bring back the "Tesla smile". So, here is his reply to our query - Thank you for your message and bringing this concern to my attention. Recently, some Model S owners have been concerned regarding displayed decreases in their vehicle's predicted range. We understand the importance of accurate range prediction, and have taken these concerns seriously. After investigating many of the cases, we have found no indications of actual battery problems in the vast majority of these cases. However, we have uncovered a software problem that, under certain charging conditions, yields incorrectly low range estimates over time. The range estimate displayed in the vehicle is based on several different factors. One important factor is the battery's actual capacity at a given point in its life. This is the amount of energy the battery can hold when fully charged. Since battery capacity cannot be measured without fully charging and discharging the battery, this value is calculated in software. We have found that in cases where the battery is consistently charged to a lower state of charge- between 60-80% -capacity estimation becomes less accurate and tends to underestimate the true capacity of the battery. The result is an incorrect reduction in the displayed range estimate. This does not affect the true range of the vehicle, as the end-of-drive conditions are based on real-time battery measurements of reducing battery power rather than software estimates. In any case we recognize the inconvenience and negative user experience associated with this incorrect and reduced range estimate and we are developing a solution. The inaccuracy of the capacity algorithm will show up in any Model S that is regularly charged under the conditions mentioned above (it seems it is the case for your Model S). We will develop and implement a firmware updates in the coming weeks (timing TBD) to address the concern you outlined. That being said, the amount of actual energy stored in the battery has not changed. The physical distance you can drive the vehicle from full to empty remains the same, only the displayed estimate has changed. You are correct that avoiding charging to high states of charge optimizes battery capacity retention. You should continue this behavior as best meets your daily range needs. We also recommend opportunistically charging, i.e, charge frequently, charge often. Avoiding deep discharges is another best practice for optimum capacity retention. The advice by the Service Center to "let the range drop down to about 20 miles and then charge it to max Daily Range" is misleading. They are correct that it will mitigate the inaccuracy of the capacity algorithm, resulting in a higher displayed range, but it is misleading as the actual amount of stored energy does not change. I hope that this addresses your concern. Please let me know if I can be of any additional assistance. Thanks for your continued support. Best regards, Jerome Guillen I VP, WW sales and service P.S. By the way we installed 5.9 last evening prior to a max Daily charge and noticed an increase of 12 miles immediately!