how long do prius batteries last? Do you really save money when the battery life will run out and they costs s?

Think of it this way - in most cars the automatic transmission has a shorter life expectancy than a Prius main battery and costs more to replace. The automatic transaxle in the Prius has no clutches, belts or other slipping devices to wear and (except for the first generation Prius, 2001-2003, which had a higher current electric motor) is essentially bulletproof.

Even my much less reliable first generation 2002 Prius has 172K miles on it, is 12 years old, and has only needed a 12 volt battery (most cars would be on their third or fourth by now), a couple of cracked windshields replaced, tires and windshield wipers plus routine maintenance. The brakes are original and less than half worn. It is by far the most reliable car I have ever owned. I do my own maintenance so I don't have a list of expenses for repairs like many people would, but it is safe to say it has saved me more than $10,000 in professional repair costs over any of the other cars I have kept for 12 years... even over the Dodge 600 I only kept 6 years. It has used less than 4000 gallons to go that far, about half what a similar Corolla or Focus would have in mostly city driving. At an average price of about $2.50 per gallon that is another $10,000. If it eventually needs a $1770 battery (remanufactured with modern cells) I will still be more than $18000 ahead. However, my battery is showing no sign of weakness.

Heck, over 12 years I have probably spent as much just on tires as a main battery replacement would be.

The high-voltage traction battery packs have been lasting a long time. 150,000-300,000+ miles in the majority of cases. There are lower-cost methods of replacing them when they degrade, such as by using savage packs from cars that were involved in collisions, that commonly cost under $1000.

The Prius has a definite cost of ownership advantage over conventional cars. The high reliability, low maintenance needs and low fuel costs combine to make ownership costs low. The Prius C is the lowest-cost car to own and operate, according to Consumer Reports.

Maintenance and repair costs for conventional autos are usually higher, such as needing to replace an automatic transmission after 200,000 miles, not including other maintenance/repair items.

There is a 12v aux battery on board which only lasts a few years. It costs ~$150-200 to replace.