Depends on what you do... we run on a Honda eu2000 (2kW) easily... no microwave or A/C... just lights, furnace fan, TV, battery re-charge. The microwave is under 1000W, so we could probably use it, but the stove works well for us.
If you need to run an A/C, pretty sure you'll need at least 3kW... but you could check the wattage ratings to double-check that.