The Honda 2000 will adequately run up to a 13000 btu A/C unit. Beyond that it gets dicey as it may not have the reserve power to kick on the compressor motor on larger units. Some sucessfully run units up to 16,000 btu with the help of a softstart capacitor. The point I want to get at is that the Honda 2000eu has a built in gas tank which holds about 1 gallon. Running a small 6000 btu in eco-throtle it can run approximately 7 hours depending on ambient temperature but running a large unit will require to turn the eco-throtle off and will only give you a run of about 3 hours. Getting up in the middle of the night to feed the generator is no fun. There is a kit being sold which would add an external 3 1/2 gallon tank which adds around 10-15 hours of running time. This means you do not have to interrupt your ssleep. You can make the connector to the external tank yourself by ordering an extra cap for your generator and getting a couple of fixtures, a fuel line and a bulb pump. The generator is great, not only will it run the A/C but can also recharge your batteries and run a microwave oven. Not all at once so plan ahead.