If generator is 4.8Kw, that is based upon upon 240v output, or 20 amps of power (4800/240).  At 120v, you only get 2.4Kw.  I think amps is the more important measure in looking at a generator.

I just had a standby generator put in, I only needed to power the downstairs 100 amp panel.  Initially, I planned to use a 13 Kw generator assuming it would be fine (13,000w/120v=108amps) until I noticed it actually was rated at 54 amps.  54 amps is not going to power a 100 amp panel.  I had to switch to a 22 Kw (92 amps) of power.