Zoo-Med UTH's are resistive heating elements, nothing regulating temperature at all... if they are hot they are working, it is as simple as that. I can say that because I'm an electrical engineer and I know the physics.
I have Progress Energy, and at least local to me my power is ok, not great but acceptable. But the power coming from every station will be different. just because it is a big company doesn't rule that out.
The problem with zoo-med products is that they advertise their products as if they didn't need a thermostat to regulate them... this is not the case. Zoo-Med UTH's will get up to 130+ within a week of being plugged in. They call it a "malfunction" because if they didn't they would have to admit that their product needed a thermostat to control it.