If a chazzan suspects that there will not be at least 9 men listening to his chazaras haShatz, he should stipulate before he starts that if that occurs, his shemoneh essrei should be a private, voluntary prayer. This cannot be done on Shabbos, Yom Tov, or any musaf.
Shabbos Bulletin Parshas Bechukosai 5779
About the Author: Lev Seltzer
Lev Seltzer has been a member of Beis Tefillah from just a short time after its founding. He currently manages the BTYA.org website, and can be found every morning in the BTYA "Vasikin Room" where he is the gabbai of the minyon.