The question is, why select a 50V rated capacitor for my 24V power rail? The answer is that users can indeed use a surface mount tantalum capacitor at or near its rated voltage with the understanding that the failure rate at this voltage condition will typically be between 0.1 and 1.0% per one thousand hours of operation. In addition, the user can expect to see increases in initial power on failure rates following board mounting. Most applications cannot accept this rate of failure however. So, to improve the reliability of the device, KEMET recommends designers follow the derating guidelines outlined in this module.