I used to have a APC SU3000RMINET 3KW UPS (5U rack model) and it would consume about 70Watts even with light loads. I think it did some kind of online conversion/smoothing. I decided to gave up on it went it died because it's more expensive in the long term then the damages it avoided during the years I had it.
Just my 50 cents...
Just my 50 cents...