The battery "warranty" is transferrable. If you want to sell the car, say 4-5 years down the road and your battery is showing signs on degradation, having the warranty may increase its value in the market, especially if new batteries from Tesla are going for, say, $20K. OTOH, if replacement batteries are going for under $15K in 2016, then you'd likely have been off investing the $12K. EDIT: One more point - there might be two battery offerings in the future. One would be the $12K pre-purchased replacement at 53KwH. Another would be an upgrade replacement at whatever Tesla wants to charge.