Warranties for batteries take two forms: number of guaranteed operational years or number of guaranteed cycles. A “cycle” refers to the battery being discharged and then re-charged. The number of cycles used in a given year will depend on how you operate your storage system. For instance, if your system is only used to provide backup power during grid outages, you may only cycle your batteries a few times a year. However, if you configure your storage system to maximize self-consumption of any solar electricity you produce, your storage system may cycle once a day. On average, lithium ion batteries are under warranty for 10 years or for 7,500 to 10,000 cycles. Lead acid batteries are under warranty for much less time, typically 2 to 5 years.