My dad purchased one of these 3500W units for $300… best deal going. Includes 220V service, 120V service, 12V service. Runs pretty smooth and surprisingly quiet for 7HP.
The UPS would stay online with the low sensitivity setting and widest berth on allowable voltages but each time the compressor would kick on in the AC because of the thermostat we would lose enough that it would have to switch to battery for a few seconds.
We are going to do some more tests this weekend with and without the power line conditioner but using APC SC 1500 UPS instead.