After reading about the Powersource 1500 for $149 at Tractor Supply, I called the local TSC store and asked. No, they did not have one nor did any store in a 100 mile radius of where I live. They DID have an 1800W unit in one store 90 miles off. It was $199 +tax.
http://www.duracellpower.com/backup-power/uninterrupted-power/powersource-1800.aspx
I asked them to put my name on it. Friday evening I traveled through the countryside and picked it up. After a day of charging, I tested the unit. It switched fine and has a display informing one of the power it is supplying.
The unit 'passes through' normal AC and when the power goes off, it comes on very quickly. The Ocilliscope shows the output to be 'modified sine wave'.
It has 3 X 17AH 12V batteries for '60AH battery'. I'm guessing it will really supply about 300Wh without killing the batteries rather rapidly.
My brother has a place 'in the country' and needed such a backup unit. It now resides with him.
Ron