Thanks Greg, your post was very helpful. I found this generator sizing chart page on Yamaha's website as I was checking out the EF2800i's specs:
http://www.yamaha-motor.com/outdoor/...or/sizing.aspx
According to this chart, a typical 10,000 BTU (= 3 kW) air conditioner needs 2.2 kW of power to start... which is beyond the Honda EU20i's 2 kW max supply. Probably explains the touchy starts.
Ideally, I'd like to be able to run appliances like an AC / heater / toaster / fridge / main laptop (in addition to astro needs) so that I can spend more time out at dark sites.
It sounds like EF2800i would be the right starting point for me. It's in a similar price range, size, and weight as the EU20i too. Do you find it much noisier than the Honda EU20i (60 vs 54 dB)? Do you get anywhere near the 17 hr rated running time on a full tank with low loads?