Just checked today due curiosity mostly, Energy Star organization and their listed database.
In about 15 minutes of time, I did discover that since 2016, a new race started regarding Uninterruptible Power Supplies of highest efficiency.
Unfortunately for most consumers, the major race starts at models supporting 3000W or higher.
Energy Star, this is American certification, and most contenders are brands interested to conquer this market.
At smallest Wattage,
750W the winner is
CyberPower - PR750ERTXL2UEfficiency at 75% Load Min Config Lowest Dependency (ac):
98.6At 3000W+ the winner is
Minuteman - EXR3000RTHVEfficiency at 75% Load Min Config Lowest Dependency (ac):
99.2And here we have an example of how product marketing this distorts true test results.
Tripp Lite - AGPS8294 : SUINT1000LCD2U
900W unit Efficiency at 75% Load Min Config Highest Dependency (ac):
96.4At their website they inform of Power Factor 1.0 ( zero losses )
Here is the link:
https://www.energystar.gov/productfinder/product/certified-uninterruptible-power-supplies/results?