If the low voltage cutoff activates then no, it then measures zero power on any normal multimeter.
While it is on, there is the LED which uses an insignificant amount compared to the camera, and all voltage converters are less than 100% efficient, not sure how efficient the HK3 is but it will be around 90%, and no voltage converter will do much better.
If the camera is not using any power because it is turned off overnight due to being parked in the garage, then the loss due to efficiency of 10% of 0 is zero, so the only power consumption is the LED, and that is probably less than 0.01 watts (haven't measured it), insignificant compared to a typical car alarm system.