Nature of Business and Basis of Presentation	3 Months Ended
Jan. 31, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Nature of Business and Basis of Presentation	Note 1. Nature of Business and Basis of Presentation FuelCell Energy, Inc., together with its 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 SureSource power plants generate electricity and usable high quality heat 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 sales of equity instruments to strategic investors or in public markets, corporate and project level debt financing and local or state government loans or grants. 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 the Company’s financial position and results of operations as of and for the three months ended January 31, 2019 and 2018 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 GAAP have been condensed or omitted. The balance sheet as of October 31, 2018 has been derived from the audited financial statements at that date, but it does not include all of the information and footnotes required by GAAP for complete financial statements. These financial statements should be read in conjunction with the Company’s financial statements and notes thereto for the fiscal year ended October 31, 2018, which are contained in the Company’s Annual Report on Form 10-K previously filed with the SEC. 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. Certain reclassifications have been made to the prior year amounts to conform to the current year presentation. The Company has adopted Accounting Standards Update ("ASU") 2014-09, "Revenue from Contracts with Customers (Topic 606)" and has applied a modified retrospective transition method. As a result of the adoption of this ASU, Unbilled receivables has been reclassified as a separate line item from Accounts receivable, net on the Consolidated Balance Sheets and Unbilled receivables has been classified as a separate item from Accounts receivable, net in the Consolidated Statement of Cash Flows for the prior year period. Liquidity The Company’s future liquidity will be dependent on obtaining a combination of increased order and contract volumes, increased cash flows from the Company’s generation and service portfolios and cost reductions necessary to achieve profitable operations. To grow its generation portfolio, the Company will invest in developing and building turn-key fuel cell projects which will be owned by the Company and classified as project assets on the balance sheet. This strategy requires liquidity and is expected to continue to have increasing liquidity requirements as project sizes increase. The Company may commence building project assets upon the award of a project or execution of a multi-year power purchase agreement (“PPA”) with an end-user that has a strong credit profile. Project development and construction cycles, which span the time between securing a PPA and commercial operation of the plant, vary substantially and can take years. As a result of these project cycles and strategic decisions to finance the construction of certain projects, the Company may need to make significant up-front investments of resources in advance of the receipt of any cash from the sale or long-term financing of such projects. These up-front investments may include using the Company’s working capital, availability under the Company’s construction financing facilities or other financing arrangements. Delays in construction progress or in completing financing or the sale of the Company’s projects may impact the Company’s liquidity. The Company expects to maintain appropriate cash and debt levels based upon its expected cash requirements for operations, capital expenditures, construction of project assets and principal, interest and dividend payments. In the future, the Company may also engage in additional debt or equity financings, including project specific debt financings under existing and new facilities. The Company believes that, when necessary, it will have adequate access to the capital markets, although the timing, size and terms of any financing will depend on multiple factors, including market conditions, future order flow and the need to adjust production capacity. There can be no assurance that the Company will be able to raise additional capital at the times, in the amounts, or on the terms required for the implementation of its business plan and strategy. In addition, the Company’s capital-intensive business model of building generation assets increases the risk that the Company will be unable to successfully implement its plans, particularly if the Company does not raise additional capital in the amounts required. If the Company is unable to raise additional capital at the times or in the amounts required, or on terms favorable to the Company, the Company’s growth potential may be adversely affected and the Company may have to modify its plans which could include restructuring, workforce reductions, change in production volumes and asset or intellectual property sales. If these strategies are not successful, the Company may be required to delay, reduce and/or cease its operations. The Company believes that its current working capital and cash anticipated to be generated from future operations, as well as recent debt incurred and cash received under its project financing facilities and remaining availability under these project financing facilities (refer to Note 14, “Debt and Financing Obligation” for more information) and proceeds from future equity offerings, will provide sufficient liquidity to fund operations for at least the next twelve months. The Company has an At Market Issuance Sales Agreement in place (refer to Note 10, “Stockholders’ Equity” for more information) which could supplement proceeds through equity offerings dependent upon market conditions. Use of Estimates The preparation of financial statements and related disclosures in conformity with GAAP 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, contract loss accruals, excess, slow-moving and obsolete inventories, product warranty accruals, loss accruals on service agreements, share-based compensation expense, allowance for doubtful accounts, depreciation and amortization, impairment of goodwill and in-process research and development intangible assets, impairment of long-lived assets (including project 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.

Nature of Business and Basis of Presentation

3 Months Ended

Jan. 31, 2019

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Nature of Business and Basis of Presentation

Note 1. Nature of Business and Basis of Presentation

FuelCell Energy, Inc., together with its 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 SureSource power plants generate electricity and usable high quality heat 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 sales of equity instruments to strategic investors or in public markets, corporate and project level debt financing and local or state government loans or grants. 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 the Company’s financial position and results of operations as of and for the three months ended January 31, 2019 and 2018 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 GAAP have been condensed or omitted. The balance sheet as of October 31, 2018 has been derived from the audited financial statements at that date, but it does not include all of the information and footnotes required by GAAP for complete financial statements. These financial statements should be read in conjunction with the Company’s financial statements and notes thereto for the fiscal year ended October 31, 2018, which are contained in the Company’s Annual Report on Form 10-K previously filed with the SEC. 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.

Certain reclassifications have been made to the prior year amounts to conform to the current year presentation. The Company has adopted Accounting Standards Update ("ASU") 2014-09, "Revenue from Contracts with Customers (Topic 606)" and has applied a modified retrospective transition method. As a result of the adoption of this ASU, Unbilled receivables has been reclassified as a separate line item from Accounts receivable, net on the Consolidated Balance Sheets and Unbilled receivables has been classified as a separate item from Accounts receivable, net in the Consolidated Statement of Cash Flows for the prior year period.

Liquidity

The Company’s future liquidity will be dependent on obtaining a combination of increased order and contract volumes, increased cash flows from the Company’s generation and service portfolios and cost reductions necessary to achieve profitable operations. To grow its generation portfolio, the Company will invest in developing and building turn-key fuel cell projects which will be owned by the Company and classified as project assets on the balance sheet. This strategy requires liquidity and is expected to continue to have increasing liquidity requirements as project sizes increase. The Company may commence building project assets upon the award of a project or execution of a multi-year power purchase agreement (“PPA”) with an end-user that has a strong credit profile. Project development and construction cycles, which span the time between securing a PPA and commercial operation of the plant, vary substantially and can take years. As a result of these project cycles and strategic decisions to finance the construction of certain projects, the Company may need to make significant up-front investments of resources in advance of the receipt of any cash from the sale or long-term financing of such projects. These up-front investments may include using the Company’s working capital, availability under the Company’s construction financing facilities or other financing arrangements. Delays in construction progress or in completing financing or the sale of the Company’s projects may impact the Company’s liquidity.

The Company expects to maintain appropriate cash and debt levels based upon its expected cash requirements for operations, capital expenditures, construction of project assets and principal, interest and dividend payments. In the future, the Company may also engage in additional debt or equity financings, including project specific debt financings under existing and new facilities. The Company believes that, when necessary, it will have adequate access to the capital markets, although the timing, size and terms of any financing will depend on multiple factors, including market conditions, future order flow and the need to adjust production capacity. There can be no assurance that the Company will be able to raise additional capital at the times, in the amounts, or on the terms required for the implementation of its business plan and strategy. In addition, the Company’s capital-intensive business model of building generation assets increases the risk that the Company will be unable to successfully implement its plans, particularly if the Company does not raise additional capital in the amounts required. If the Company is unable to raise additional capital at the times or in the amounts required, or on terms favorable to the Company, the Company’s growth potential may be adversely affected and the Company may have to modify its plans which could include restructuring, workforce reductions, change in production volumes and asset or intellectual property sales. If these strategies are not successful, the Company may be required to delay, reduce and/or cease its operations.

The Company believes that its current working capital and cash anticipated to be generated from future operations, as well as recent debt incurred and cash received under its project financing facilities and remaining availability under these project financing facilities (refer to Note 14, “Debt and Financing Obligation” for more information) and proceeds from future equity offerings, will provide sufficient liquidity to fund operations for at least the next twelve months. The Company has an At Market Issuance Sales Agreement in place (refer to Note 10, “Stockholders’ Equity” for more information) which could supplement proceeds through equity offerings dependent upon market conditions.

Use of Estimates

The preparation of financial statements and related disclosures in conformity with GAAP 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, contract loss accruals, excess, slow-moving and obsolete inventories, product warranty accruals, loss accruals on service agreements, share-based compensation expense, allowance for doubtful accounts, depreciation and amortization, impairment of goodwill and in-process research and development intangible assets, impairment of long-lived assets (including project 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.