I'm just posting this for anyone who has been as curious as I have about what UPS output waveforms look like. I knew it wasn't a sine wave, and electric motors in particular really don't do well with it. But I wasn't expecting a square wave. I was also expecting a little more of a perfect sine wave from my utility. Anyway here's the output from an old APC 280 backups:

My utility power from the wall:


UPS output no-load:


UPS output small fan as a load, probably 10-20 watts:

 

My off-grid UPS output is as good or better than the utility

You get what you pay for. http://www.xantrex.com/power-products/power-inverters/prowatt-sw.aspx

 

Your utility wave looks far better than mine.