They require a lot more power on startup than continuous use. Make sure you account for that.I don't know what size it is. The house is just under 1100 sq ft.
When I was looking for a generator everything I read said an A/C will use about 1000 watts per hour per ton rating. So a 2.5 ton A/C unit should use 2500 watts per hour while in cooling mode. 8500 continuous watts should be sufficient if that's the case.