I believe around 3k or a low miles used 800 to 1000. The old battery is worth 200 on return. I know of no postings of battery replacement ( failure) on a 04 that would be covered. There are a few reports of battery failure and replacement in the 200k to 250k miles range that have been posted. Lots of posts of 100k miles and no problems. Battery life seems to be a non issue so far. Price of batteries should come down by the time the 04's start needing new batteries. I would hope by then many model lines will have a hybrid option. Who know GM may even build a real hybrid. The fabled hybrid hummer getting say 12 mpg.