Nature of Business and Basis of Presentation	3 Months Ended
Jan. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Business and Basis of Presentation	Nature of Business and Basis of Presentation FuelCell Energy, Inc. and subsidiaries (the “Company”, “FuelCell Energy”, “we”, “us”, or “our”) is a leading integrated fuel cell company with a growing global presence. We design, manufacture, install, operate and service ultra-clean, efficient and reliable stationary fuel cell power plants. Our Direct FuelCell power plants continuously produce base load electricity and usable high quality heat around the clock for commercial, industrial, government and utility customers. We have commercialized our stationary carbonate fuel cells and are also pursuing the complementary development of planar solid oxide fuel cells and other fuel cell technologies. Our operations are funded primarily through cash generated from product sales, service and advanced technologies contracts, license fee and royalty income and sales of equity and debt securities. In order to produce positive cash flow from operations, we need to be successful at increasing annual order volume and production and in our cost reduction efforts. Basis of Presentation The accompanying unaudited consolidated financial statements have been prepared in accordance with the rules and regulations of the Securities and Exchange Commission (“SEC”) regarding interim financial information. Accordingly, they do not contain all of the information and footnotes required by accounting principles generally accepted in the United States of America (“GAAP”) for complete financial statements. In the opinion of management, all normal and recurring adjustments necessary to fairly present our financial position and results of operations as of and for the three months ended January 31, 2016 have been included. All intercompany accounts and transactions have been eliminated. Certain information and footnote disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States of America have been condensed or omitted. The balance sheet as of October 31, 2015 has been derived from the audited financial statements at that date, but it does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements. These financial statements should be read in conjunction with our financial statements and notes thereto for the year ended October 31, 2015, which are contained in our Annual Report on Form 10-K previously filed with the Securities and Exchange Commission. The results of operations for the interim periods presented are not necessarily indicative of results that may be expected for any other interim period or for the full fiscal year. Use of Estimates The preparation of financial statements and related disclosures in conformity with accounting principles generally accepted in the U.S. requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses and the disclosure of contingent assets and liabilities. Estimates are used in accounting for, among other things, revenue recognition, excess, slow-moving and obsolete inventories, product warranty costs, accruals for service agreements, allowance for uncollectible receivables, depreciation and amortization, impairment of goodwill, indefinite-lived intangible assets and long-lived assets, income taxes, and contingencies. Estimates and assumptions are reviewed periodically, and the effects of revisions are reflected in the consolidated financial statements in the period they are determined to be necessary. Due to the inherent uncertainty involved in making estimates, actual results in future periods may differ from those estimates. Related Parties POSCO Energy (“POSCO”), which is a related party, owned approximately 9.0% of the outstanding common shares of the Company as of January 31, 2016. Revenues from POSCO Energy for the three months ended January 31, 2016 and 2015 represent 45% and 54%, respectively, of consolidated revenues. NRG Energy, Inc. ("NRG") is a related party and owned approximately 5.0% of the outstanding common shares of the Company as of January 31, 2016. NRG Yield is a dividend growth-oriented company formed by NRG Energy, Inc. that owns, operates and acquires a diversified portfolio of contracted renewable and conventional generation and thermal infrastructure assets in the United States. Revenues from NRG and NRG Yield for the three months ended January 31, 2016 and 2015 represents 0.2% and 5.0%, respectively, of consolidated revenues.

Nature of Business and Basis of Presentation

FuelCell Energy, Inc. and subsidiaries (the “Company”, “FuelCell Energy”, “we”, “us”, or “our”) is a leading integrated fuel cell company with a growing global presence. We design, manufacture, install, operate and service ultra-clean, efficient and reliable stationary fuel cell power plants. Our Direct FuelCell power plants continuously produce base load electricity and usable high quality heat around the clock for commercial, industrial, government and utility customers. We have commercialized our stationary carbonate fuel cells and are also pursuing the complementary development of planar solid oxide fuel cells and other fuel cell technologies. Our operations are funded primarily through cash generated from product sales, service and advanced technologies contracts, license fee and royalty income and sales of equity and debt securities. In order to produce positive cash flow from operations, we need to be successful at increasing annual order volume and production and in our cost reduction efforts.

Basis of Presentation

The accompanying unaudited consolidated financial statements have been prepared in accordance with the rules and regulations of the Securities and Exchange Commission (“SEC”) regarding interim financial information. Accordingly, they do not contain all of the information and footnotes required by accounting principles generally accepted in the United States of America (“GAAP”) for complete financial statements. In the opinion of management, all normal and recurring adjustments necessary to fairly present our financial position and results of operations as of and for the three months ended January 31, 2016 have been included. All intercompany accounts and transactions have been eliminated.

Certain information and footnote disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States of America have been condensed or omitted. The balance sheet as of October 31, 2015 has been derived from the audited financial statements at that date, but it does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements. These financial statements should be read in conjunction with our financial statements and notes thereto for the year ended October 31, 2015, which are contained in our Annual Report on Form 10-K previously filed with the Securities and Exchange Commission. The results of operations for the interim periods presented are not necessarily indicative of results that may be expected for any other interim period or for the full fiscal year.

Use of Estimates

The preparation of financial statements and related disclosures in conformity with accounting principles generally accepted in the U.S. requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses and the disclosure of contingent assets and liabilities. Estimates are used in accounting for, among other things, revenue recognition, excess, slow-moving and obsolete inventories, product warranty costs, accruals for service agreements, allowance for uncollectible receivables, depreciation and amortization, impairment of goodwill, indefinite-lived intangible assets and long-lived assets, income taxes, and contingencies. Estimates and assumptions are reviewed periodically, and the effects of revisions are reflected in the consolidated financial statements in the period they are determined to be necessary. Due to the inherent uncertainty involved in making estimates, actual results in future periods may differ from those estimates.

Related Parties

POSCO Energy (“POSCO”), which is a related party, owned approximately 9.0% of the outstanding common shares of the Company as of January 31, 2016. Revenues from POSCO Energy for the three months ended January 31, 2016 and 2015 represent 45% and 54%, respectively, of consolidated revenues.

NRG Energy, Inc. ("NRG") is a related party and owned approximately 5.0% of the outstanding common shares of the Company as of January 31, 2016. NRG Yield is a dividend growth-oriented company formed by NRG Energy, Inc. that owns, operates and acquires a diversified portfolio of contracted renewable and conventional generation and thermal infrastructure assets in the United States. Revenues from NRG and NRG Yield for the three months ended January 31, 2016 and 2015 represents 0.2% and 5.0%, respectively, of consolidated revenues.