​Since the live ball era began in 1920, a 20-homer season by a switch hitter has been accomplished 261 times by 67 players. 
Which begs the question—how many switch hitters have clubbed at least 10 or more homers from both sides of the plate in the same season? 
The answer: It has been achieved 64 times by 33 players—with only Mickey Mantle, Howard Johnson, Chipper Jones, Ken Caminiti, and Mark Teixeira the only players to hit 15 or more homers from both sides of the plate in the same season.
The highest total of homers hit from both sides of the plate in the same season is 16 or more by Mantle, who hit 24 from the left side and 16 from the right in 1960 when he finished the year with 40 homers. The Yankee legend holds the mark with most seasons hitting 10 or more homers as a lefty and righty hitter in the same year with six.