Cover Page - shares	6 Months Ended
	Mar. 31, 2021	May 03, 2021
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2021
Document Transition Report	false
Entity File Number	001-12488
Entity Registrant Name	Powell Industries, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	88-0106100
Entity Address, Address Line One	8550 Mosley Road
Entity Address, City or Town	Houston
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	77075-1180
City Area Code	713
Local Phone Number	944-6900
Title of 12(b) Security	Common Stock, par value $0.01 per share
Trading Symbol	POWL
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		11,691,673
Entity Central Index Key	0000080420
Amendment Flag	false
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Current Fiscal Year End Date	--09-30