The better information that is provided when asking a question the more targeted the responses will be. To answer your question, yes you should be able to run the water heater from your current outlets but nothing else at the time the heating element is energized. Like Hello Bellow explained a Honda 2000 generator only runs 1600W of power in a "continuous" capacity so there is no adequate power reserve to prevent an overload should another load be added or come on line. (this would require for the generator engine to be in good state of tune) I would truly favor using an extension cord 10 or 12 gauge directly to the water heater just to heat water when it is needed. If maintaining hot water for hours is required than a larger generator would be needed. Larger generators than the 2000W class are usually much heavier and bulkier with poor weather proofing.