Yes , those detectors depending on the age and model can draw up to a full amp. That plus the 1/2 amp or more from the fridge on gas, the radio, the TV if its plugged in, all add up to a sleepy battery by morning.
I put a temp volt/amp meter in line so I can see exactly how much power each item draws while using it.
I do not use an LP detector as of now, but I do spray my fittings 2x a season to check for leaks. I have never had any kind of leak since 1969. My DW's nose will tell me if I have a leak somewhere. The OEM LP detector is also a Methane detector, ask my dog who sleeps next to it at 3 AM.
They did make a couple of them that were battery operated. The TC guys used them while off grid hunting/fishing. One looked like a pen. The other were Kidde style detectors.
When I recently did a search for a battery model, the initial description in bold letters said 'plug-in' but when I clicked 'more details' it said battery powered too.
" ... Kidde Nighthawk Plug-In AC/DC Carbon Monoxide Alarm Detector with Digital Display KN ... Amazon Business : For business-only pricing, quantity discounts and FREE Shipping."
hand-held models avl too
"Y201 Propane and Natural Gas Leak Detector; Portable Gas Sniffer to Locate Gas Leaks of Combustible Gases like Methane, LPG, LNG, Fuel, Sewer Gas; w/ Flexible Sensor Neck, Sound & LED Alarm,"
Using Amazon Prime allows us to simply return it , all paid shipping. That's what I have been doing. If its not what I expected, I send it back. Sometimes they tell me to 'not bother, keep it' and refund me . That usually happens with electronic cords and connectors. Have not tried that on other items yet.
Bob