I heard from someone that they use either 15-minute OR HOURLY demand from smart meters to do optional calc 220.87 to see actual demand. I know the 15-minute demand data for 1 year is good per 220.87, but, looking at the NEC, I can't find this 15-minute increment mentioned anywhere. Is it acceptable to use the 1-hour interval, which will obviously result in a lower peak demand? Can someone point me to a definition of how long the interval should be? I've got a multifamily building that's got some meters on 15-minute and some on 1-hour, and I'd love to just do the calc with the data I have.