Hearing aid batteries have come a long way in the last couple of decades. During that time they have also become much more standardized making it easier for the consumer to find and purchase hearing aid batteries as simple as choosing one of four different colors: 
These times are of course on average and can vary on many things such as volume, gain, and even altitude (where aids last a shorter amount of time). There are also rechargeable batteries available on the market. On average you can expect to pay about $60.00 per pair for rechargeable batteries and another $170 for the actual charger itself. Traditional disposable batteries will run about 50 cents a piece when purchased in 40 packs. Always remember to remove the protective seal before inserting the battery into the hearing aid and leave the battery door open for 2 to 5 minutes to activate the battery. Once the seal is removed the battery will begin discharging. As always, if you have any questions on batteries or anything else, let us know!