You can expect to burn a whopping 800 calories per hour if you’re on a setting that feels right for you. Something that’s not too heavy, and not too light either.
A light workout on a low resistance setting would be more like 500 calories per hour, which is much closer to what you’d expect to burn on a treadmill.
On the other hand, if you really went ham on your vertical climber, you could burn up to 1000 calories per hour… until you start slowing down to what you can handle, which, of course, brings your average down again.
Either way, you don’t have to guess how many calories you’re burning. The vertical climbers out there that are worth getting almost always have an LCD display which tells you exactly how many calories you’ve burned during that session.