A:Answer 300 watts, 25 amp, 12 volt DC.
(The last photo of the product box, if you zoom in on it, it shows "300 watts")
The heater (all) are likely protected against overheating to prevent damaging themselves.
*With all heaters, use caution that they aren't blowing on/pointing at anything very close to them, as that could cause damage. Example, the seat, papers, clothing, etc.
Continuous use won't damage anything except it will drain a vehicle battery (an old one much faster) so the vehicle engine should be running to help prevent that drain. It could also be used for a short period, turn it off, use it again, to minimize that drain, but you'd still want the vehicle engine running. This heater uses about the same power as 5 halogen off-road lights. That high power is why it has a high heat output.