Re: Online UPS as off-grid inverter?
My experience with using a UPS as an inverter is similar to fca1.
I have an old APC Matrix 5000 UPS. I experimented with it running off grid for part of a day once in a while. I used the Matrix 5000 before I got my XW6048 inverter. The Maxtrix worked very well as long as loads were kept under the 5000 VA limit. Even a small surge above the rating, and the UPS would shut down immediately. It's not that the hardware of the UPS probably couldn't handle some surge, but the software/firmware of the UPS is programmed to shut down when the limit is exceeded.
Also, as mentioned by fca1, the power consumption of the UPS was higher than a good inverter under idle and low load conditions. At high loads, the Matrix 5000 was quite efficient (in the 90's %) when I calculated the efficiency. At low loads, efficiency was much worse. I still have the Matrix 5000 and it is my backup in case the XW6048 is out of commission for some reason.
Finally, I would think it would be hard to live off grid with only 1400 VA of power (with no surge capability). It might be possible, but you would need to keep your loads very minimal and stay away from any large motor appliances.
On-grid with RE backup power. HY-2000 2kW wind turbine charging 48V 600Ah Concorde Lifeline battery bank. Wind power diversion heats water in an auxilliary 80 gal hot water heater. 2.1kW Evergreen solar panels & TS-MPPT-45. XW6048 inverter, Onan 6kW 6DJE diesel generator, and Yanmar YDG3700 diesel gen as backup.