Is it hot in here?

Is anyone else having an issue with a toasty second floor?  We thought it was crazy to have a 3,000 sq ft house with only one unit for a/c, but our SR assured us that it would be fine "because its energy star."  Yeah right!!  I am just curious if there is something wrong with ours or whether we aren't the only ones with this problem.  There is a significant change in temperature upstairs...it's going to be a long summer.