I always set my nap alarm for 30 minutes until my sister in Tulsa showed me a chart
I used to swear by a 30 minute nap alarm, but my sister pulled up a sleep chart on her phone during Thanksgiving in Tulsa that showed most people don't hit deep sleep until around the 30 minute mark. So when my alarm goes off right at 30, there's a good chance I'm yanking myself out of the deepest part of the cycle, which is why I'd wake up foggy for an hour. She sets hers for 20 minutes and swears she pops up clear headed every time. I tried it for a week and honestly the 20 minute version leaves me way less groggy. Has anyone else messed with 20 vs 30 and noticed a real difference, or is it just me?
That bit about yanking yourself out of the deepest part of the cycle is the whole thing right there. I read somewhere that a full cycle runs about 90 minutes, so 20 minutes keeps you in the light sleep stage where waking up is easy, while 30 can dump you right into the start of deep sleep. My trick is setting the alarm for 22 minutes and giving myself a couple minutes to actually drift off, since lying there staring at the ceiling eats into the clock. The grogginess difference for me was night and day.