I wonder what is the battery performance increase rate from development. Currently some already stated that batteries improve at a rate of about 7 to 8% a year. I am very much beyond skeptical about the fact. Already there are signs that the next-generation battery for the model three will be about 10 to 15% better. Realistically the biggest determining factor in battery performance is the chemistry and that is not increasing at a very fast rate at all. It is not like electronics or software, chemistry development is in fact slow and painstaking. Both the research is slow and then even testing the battery takes even more time just to find out that it doesn't perform on one of the tests. There are roughly about five categories to which a battery has to perform, not just energy capacity per weight. But we must provide good energy capacity per mass and volume. While lithium air batteries can increase today's batteries capacity per weight by 15 fold, their lifespan of about eight cycles of charge and discharge makes them currently quite useless. An automobile battery must also be powerful and have a high rate of charge and discharge. Super capacitors are amazing at extremely quick charge and discharge but fail miserably in terms of actually storing a lot of energy. An automobile battery must be cheap to produce. Replacing expensive and toxic metals with anodes and cathodes made from sulfur and silicone can make battery production a lot cheaper. But their limitation in durability currently makes them not so good for automotive use. The battery must be able to deal with extreme temperature changes. The temperature management system definitely can help when the vehicle is traveling. But even the storing of battery in a very hot climate inside the vehicle that with all of the class outside greenhouse effect can greatly reduce the lifespan of the battery. Using the battery in extreme cold, before the battery warms up, and for example make lithium ion batteries reduction in life and performance. It seems that the worse the chemistry in terms of performance like lead acid or nickel cadmium, the better they are at handling wild swings in temperature. The biggest cost factor in owning an electric vehicle is the replacement cost of the battery. Durability of a battery is therefore paramount. Already solid-state batteries have the advantage of up to 10 full durability compared to today's liquid electrolyte lithium-ion batteries. But their low power limits their charging and discharging rates to below what is acceptable for an electric vehicle. Even storing the battery at high temperature can greatly reduce its life. Side reactions usually increase with temperature in the side reactions are usually nonreversible and slowly chewing up the reactants inside the battery wearing it out. There's also corrosion increasing with temperature which also shortens the life of the battery with age at higher temperature. Since the new battery must be able to perform well in all five categories it is hard to find chemistry that does just that and so realistically it seems to be safe and conservative estimate than battery improvement is roughly about 2% a year. The model three will be released in 2017 and I likely have a 10 to 15% improvement in battery over the 2012 Model S. I calculated the improvement from a number of years between car development and the percent increase in battery density per mass. The more optimistic look yields about 3% improvement a year. I'm curious to what most people think the battery development rate is? There's a lot of optimistic exaggeration but if you look down on what has actually been released in what type of time frame than one can see future electric vehicles to have similar performance to today's in the next five years. Yes 10 to 15% improvement is actually fairly noticeable for the average commute, but it's not going to change how one drives the EV in terms of planning and range of use.