Thanks for all the replies.
The two priorities for this during a power outage are to keep my sump pump going if necessary -- this was an issue when Irene hit the northeast, and I was lucky I didn't spend a night with bailing buckets -- and ensure food doesn't spoil in my deep freezers. Both of these chores can easily be handled by a 2 KW unit... especially since it's not necessary that either device be powered continuously. I'd also probably want to run a computer or two, but they don't use too much.
I'm not sure about "easily," especially since you're talking about more than one freezer.
Electric motors require several times their normal rated draw for startup. For example, a single 800 watt electric motor can draw 2,400 watts during startup. While this is a very brief transient load, if the generator is only rated at 2 KW max, the "800 watt" motor won't start because the 2 KW generator won't be able to supply the 2.4 KW startup surge.
Basically, even though a 2 KW generator can probably run the sump pump and a couple of freezers at their continuous draw (the rated power on the stickers for the appliances), it's going to have difficulty with the startup surge and may not be able to start even one appliance, and will definitely have problems.
A freezer is better than a refrigerator, admittedly (my refrigerator pulls 11.6 amps or about 1.3 KW but the deep freeze only pulls 5 amps, or about 550 watts), but it's pretty iffy whether a 2 KW generator could handle the startup surge for the sump pump if both freezers were already running. Granted, it may not be terribly likely that both freezers would be running at the same time.
Now, if you mean that you'll physically be un-plugging appliances from the generator and moving it to other appliances to distribute the load, then I think a 2 KW generator would be fine. I just have my doubts about it being able to start a sump pump if there is already a load on it from a freezer or two.
If you were thinking of plugging everything into the generator and leaving it like that for the duration of the outage though, I'd want a 5 KW unit for peace of mind.
ZV