By doing so, you essentially make the 3000 ups become a 2200 ups.
First, understand that 3000, 2200, 1400, 5000, etc are VA ratings for the ups. VA is volt-amperes. Its the electrical capacity of the UPS. It has nothing to do with runtime, size, etc. VA is volts times amps.
So when your 3000va ups is using a 20amp plug, its limited to 'pulling' 20amps or 20 x 120 = 2400 volt amps.
Considering a 3000va UPS uses the same batteries and frame as the 2200va system, you might as well buy the 2200. 3000va systems are usually $100-150 more than the 2200v version.
If you are concerned about load ratios of the UPS, it is true that the 3000va is obviously built to handle the larger electrical demand. In those cases, using a 3000va on a 20amp circuit does ensure a better load ratio than a 2200va system. I dont think its worth the extra money though.
Final note. this only is applicable to 120volt systems
