Not really practical, edubb, unless you have a very, very large battery bank. And the cost of that battery bank plus the big inverter plus a hefty charger kind of defeats the purpose of undersizing the genset, doesn't it?

The problem in this scheme is the amount of current (amps) the inverter has to draw from batteries to power an a/c unit. It takes 10x as many DC amps (@12V) as it does AC amps (@120V) to run the a/c. So your a/c, which is using 11-13 amps causes the inverter to pull at least 110-130 amps from the batteries continuously. Actually more, because the conversion is not 100% efficient. That's a huge load, especially when you consider a typical battery has 85-110 amp hours total capacity and only about half that is usable before the voltage drops real low. To avoid burning up batteries at that kind of load, you would need at least 6 batteries and perhaps 8 or more, with appropriate large gauge wiring. Then you want a 100+ amp charger to help keep up with the power draw. That means 10+ amps @120 VAC from the genset just to run the charger. See where I'm going with this?

A genset has a built-in buffer for short term loads like compressor start-up. That's why gensets have two power rating numbers - continuous and peak. It's usually the larger peak number you see advertised, but if you had a genset that can handle the a/c load continuously, it probably has enough peak power to handle the compressor start load. And if it does, none of these schemes are necessary. A 1500-1600 watt *continuous* genset will run an a/c unit (with no other loads) because it probably has a peak rating of 1850-2000 watts that it can handle for at least a couple minutes. The surge from the compressor is over in a second or two, so the peak load is easily within the gensets capability. But we know that it's never just the a/c running, so from there we start building toward ever larger gensetsto make sure there is capacity for the worst case