CCDSoft shows the percentage of power used to regulate the temperature: "The temperature setpoint is normally degrees below the ambient temperature. For SBIG cameras, the camera's thermal electric cooling (as a percentage of its maximum cooling capacity) is displayed on the Camera Control Panel. Try to keep this value below 90 percent." It would be nice to have this feature in Maxim to avoid driving the TEC at maximum for all cameras.
It is supposed to be visible, if supplied by the camera, here: http://www.cyanogen.com/help/maximdl/HIDD_INSPECT.htm
It is visible when the cooler is on. There typically isn't a way to limit TEC power directly, as that's handled internally to the camera's driver/firmware — but once your camera gets down to the setpoint, maintaining the sensor's temperature should not require 90% of the camera's cooler power. You just have to make sure the camera has good airflow, and the setpoint isn't below the cooler's ΔT.
You don't want the cooler power hitting 100% during normal operation, because that means the cooler can't regulate. 90% is a target recommended by some, as it gives a bit of headroom. It should still be able to regulate into the high 90's, except of course if the ambient temperature goes up then it will run out of headroom. Fortunately the ambient temperature usually drops at night.
