Earlier in Powell's hearing, Sen. Sherrod Brown, D-Ohio, commended Yellen for an "excellent job" and said she presided over "one of the longest expansions" in history, "an expansion we still enjoy."
"Her strong and steady stewardship of an independent central bank following the worst financial crisis since the Great Depression ensured we did not repeat those mistakes," Brown said.
The central bank is on a course of gradual normalization from its financial crisis-era policies. After holding its benchmark rate near zero for seven years, the Fed has hiked four times since December 2015 and is widely expected to add another in a few weeks.
Powell said it's Fed policy not to commit to votes ahead of Federal Open Market Committee meetings, where monetary policy is set.
In fact, his refusal to deviate from the well-traveled Fed script drew some market criticism.
"Fed Chair nominee Jerome Powell's hearing in front of the Senate banking committee this morning contained few signs that he will bring any new thinking or a change of approach to the FOMC," Michael Pearce, U.S. economist at Capital Economics, said in a note. "With fewer qualified and experienced members on the Committee in decades, we are increasingly worried that a policy mistake in either direction is possible in the years ahead."
Powell echoed some recent comments from other Fed officials who are concerned about the importance of not falling behind the curve as the economy strengthens and the labor market tightens, even at a time when some have not enjoyed the benefits of the recovery.
Markets have appreciated Yellen during her time, with booming stocks, still-low interest rates and below-trend economic growth. Critics worry, though, that the recovery has been lopsided, tilted toward the top earners, with imbalances beginning to form in financial markets.
Stocks rose during Powell's testimony.
"It's important to say we are raising rates now because the economy is strong and if we wait too long ... the economy would overheat," Powell said in response to a question about low wage growth. "We'd have to raise rates and then the economy would have a recession. That wouldn't help those people. The best way to sustain the recovery, I believe, is to continue on this path of gradual rate increases."
In addition to the rate hikes, Powell said the Fed is going to continue to decrease the size of its $4.5 trillion balance sheet, made up largely of bonds the central bank bought to stimulate the economy.
The Yellen Fed enacted the first rate hike in more than nine years and began the roll-off of the balance sheet.
"That process should take three or four years before we reach our new stable level of the balance sheet," he said.