I've been doing yoga the past 10 months, after transitioning out of long distance running due to some injuries, and if you go to a tough studio that dose power vinyasa, hot yoga or some other form of high cardio yoga, it definitively will kick your arse. When I wear my apple watch to check calories it'll put me at about 800-850 calories for a 90 min class (heart rate can hit around high 160s, but average 125-140, which isn't bad for 90 min) whereas if I do a 30 min run, it will read out about 275 calories (avg HR 160s). I'm not particularly good at it, as I have zero inherent flexibility.
Avoid the slow, stretching "yin" yoga stuff if you want an actual work out, it's generally a waste of time. That's good for flexibility only (not that that doesn't have value). I also try to stay away from the chanting, sanskrit nonsense-babble and all that hokum smokum. I'm not in it for enlightenment, just for the work out. (And the hot chicks in yoga pants.)
I do know this, though, if I sent any of my patients to the yoga classes I do, they'd probably get dragged out of there on a back board, and sue me for pain and suffering, cuz it's a helluva lot harder than it looks.
