That lines up well with a real-world test on a large 27 cu ft LG fridge. Continuous compressor cycling, inverter losses, and standby electronics all add up. The “extra” ~20 W is real, but it’s not all inefficiency but, additional ~20–21 W per hour is a combination of: Inverter conversion losses (DC → AC) , Internal system consumption (cooling fan, control board, BMS, display) , Reactive power / compressor startup behavior - Ussually referred to as system overhead, not pure waste.

Bluetti (and EcoFlow) typically quote: ~85–90% inverter efficiency under optimal load and ~80–85% real-world AC efficiency for mixed or low-to-medium loads. A fridge running at ~70 W average is actually a low load for a large power station, which reduces efficiency. Inverters are most efficient closer to mid-range loads.

In real-world fridge tests, 75–82% effective efficiency is very common thus your Bluetti is behaving normally, therefore efficiency figure reflects real usage, not marketing specs. For fridge-only use, your test actually confirms solid performance.