Overview and Summary of Significant Accounting Policies	9 Months Ended
Overview and Summary of Significant Accounting Policies	Jun. 30, 2021
Accounting Policies [Abstract]
Overview and Summary of Significant Accounting Policies	Overview and Summary of Significant Accounting Policies Overview Powell Industries, Inc. (we, us, our, Powell or the Company) was incorporated in the state of Delaware in 2004 as a successor to a Nevada company incorporated in 1968. The Nevada company was the successor to a company founded by William E. Powell in 1947, which merged into the Company in 1977. Our major subsidiaries, all of which are wholly owned, include: Powell Electrical Systems, Inc.; Powell (UK) Limited; Powell Canada Inc.; and Powell Industries International, B.V. We develop, design, manufacture and service custom-engineered equipment and systems which (1) distribute, control and monitor the flow of electrical energy and (2) provide protection to motors, transformers and other electrically powered equipment. We are headquartered in Houston, Texas and serve the oil and gas markets, including onshore and offshore oil and gas production, petrochemical, liquefied natural gas (LNG) terminals, pipeline, terminal, mining and metals, light rail traction power, electric utility, pulp and paper and other heavy industrial markets. Impact of the COVID-19 Pandemic and Oil and Gas Commodity Market Volatility on Powell Through the first nine months of Fiscal 2021, the COVID-19 pandemic continues to impact global energy markets. This pandemic has negatively impacted demand, which in turn has resulted in considerable volatility across global oil and gas commodity markets. As a result, some of our industrial customers are deferring or suspending their planned capital expenditures. Certain of our customers have asked that we delay or cancel our manufacturing on their projects as their operations have been negatively impacted by this pandemic and the reduced oil and gas demand which has resulted in recognition of cancellation fees based on contract terms and the extent of our progress on the projects. We continue to work with and review the contracts with our key suppliers who have been impacted by this pandemic to ensure that we are able to meet our customer commitments. The consequences of a prolonged global economic decline could include, but are not limited to, a continued reduction in commercial and industrial activity. Accordingly, the Company cannot reasonably estimate the duration or severity of this pandemic, or the extent to which the disruption may materially impact our business, results of operations or cash flows. We will take prudent measures to maintain our strong liquidity and cash position, which may include reducing our capital expenditures and research and development costs, as well as reducing or eliminating future dividend payments. Basis of Presentation These unaudited condensed consolidated financial statements include the accounts of Powell and its wholly-owned subsidiaries. All significant intercompany accounts and transactions have been eliminated in consolidation. These unaudited condensed consolidated financial statements have been prepared in accordance with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X for interim financial information. Certain information and footnote disclosures, normally included in annual financial statements prepared in accordance with accounting principles generally accepted in the United States (U.S. GAAP), have been condensed or omitted pursuant to those rules and regulations. In the opinion of management, all adjustments, consisting only of normal recurring adjustments, necessary to fairly state the financial position, results of operations and cash flows with respect to the interim condensed consolidated financial statements have been included. The results of operations for the interim periods are not necessarily indicative of the results for the entire fiscal year. We believe that these financial statements contain all adjustments necessary so that they are not misleading. These unaudited condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto of Powell and its subsidiaries included in Powell’s Annual Report on Form 10-K for the year ended September 30, 2020, which was filed with the Securities and Exchange Commission (SEC) on December 9, 2020. References to Fiscal 2021 and Fiscal 2020 used throughout this report shall mean our fiscal years ended September 30, 2021 and 2020, respectively. Use of Estimates The preparation of condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in the condensed consolidated financial statements and accompanying footnotes. The most significant estimates used in our condensed consolidated financial statements affect revenue recognition and estimated cost recognition on our customer contracts, the allowance for credit losses, provision for excess and obsolete inventory, warranty accruals and income taxes. The amounts recorded for warranties, legal, income taxes, impairment of long-lived assets (when applicable), liquidated damages and other contingent liabilities require judgments regarding the amount of expenses that will ultimately be incurred. We base our estimates on historical experience, forecasts and various other assumptions, as well as the specific circumstances surrounding these contingent liabilities, in evaluating the amount of liability that should be recorded. Additionally, the recognition of deferred tax assets requires estimates related to future income and other assumptions regarding timing and future profitability because the ultimate realization of net deferred tax assets is dependent on the generation of future taxable income during the periods in which temporary differences become deductible. Estimates routinely change as new events occur, additional information becomes available or operating environments change. Actual results may differ from our prior estimates. New Accounting Standard In June 2016, the Financial Accounting Standards Board (FASB) issued a new topic on measurement of credit losses. The topic introduces an impairment model known as the current expected credit loss (CECL) model that is based on an expected loss methodology rather than an incurred loss methodology for financial instruments. Under the new topic, an entity recognizes as an allowance its estimate of expected credit losses with the intention of improving financial reporting by requiring timelier recognition of such losses. We adopted this topic on October 1, 2020 and such adoption did not have a material impact on our consolidated financial statements.