NEW YORK ( TheStreet) -- Americans like to think they're sunny and optimistic when it comes to retirement. You know the drill. Work until you're 65 or so, then pull up stakes and buy a home somewhere warm and sunny. Work on your golf game, travel a bit and enjoy your golden years as nature intended. But is that a realistic goal these days? A study from Charles Schwab ( SCHW) says "maybe not." That study suggests Americans are "underestimating" their financial needs in retirement, even as most U.S. adults say they are prepared for calling it a career. The Schwab study of 1,800 U.S. investors says 84% of them say they "have a retirement plan in place" and 80% say they are "confident" of their ability to retire comfortably. But Americans aren't aiming high enough on their retirement income, Schwab says. The report notes that study participants say they'll need $66,000 in annual income in retirement, way below their current annual income of $115,000. Most financial advisers want their clients to have at least 75% of their annual income in retirement, which means the Schwab study participants won't have enough cash to retire in reasonable comfort. "Everyone's retirement saving and investing plan is going to be unique, but each plan needs to start with a realistic assessment of personal situation and goals," says Carrie Schwab-Pomerantz, Charles Schwab's senior vice president and a certified financial planner. "In many cases, we tell clients to assume they'll need roughly the same annual income in retirement as they had beforehand unless they anticipate a significant lifestyle change, and to take into account longevity risk when planning how much money they might need."