The average cost is around $100, though more premium brands can cost twice as much at $200 if not more. The cost of a battery depends heavily on the size and other specifications. Brands have vastly different prices as well. Your local car shop may change the battery on your car for free if you buy a battery from them, otherwise the cost of changing it will depend on your vehicle. Some vehicles have very easy access to the batter while some are notoriously difficult to reach. Ask for a quote from your local repair shop.