Consolidated Statements of Operations - USD ($) $ in Thousands		12 Months Ended
		Oct. 31, 2021	Oct. 31, 2020	Oct. 31, 2019
Revenues:
Revenues		$ 69,585	$ 70,871	$ 60,752
Costs of revenues:
Costs of revenues		85,224	78,596	82,021
Gross loss		(15,639)	(7,725)	(21,269)
Operating expenses:
Administrative and selling expenses		37,948	26,644	31,874
Research and development expenses		11,315	4,797	13,786
Total costs and expenses		49,263	31,441	45,660
Loss from operations		(64,902)	(39,166)	(66,929)
Interest expense		(7,363)	(15,294)	(10,623)
Change in fair value of common stock warrant liability		(15,974)	(37,086)
Extinguishment of Series 1 preferred share obligation		(934)
(Loss) gain on extinguishment of debt and financing obligation		(11,156)	1,801
Other (expense) income, net		(694)	684	93
Loss before provision for income taxes		(101,023)	(89,061)	(77,459)
Provision for income taxes		(2)	(46)	(109)
Net loss		(101,025)	(89,107)	(77,568)
Net income attributable to redeemable noncontrolling interest		30
Net loss attributable to FuelCell Energy, Inc.		(101,055)	(89,107)	(77,568)
Series B preferred stock dividends		(3,200)	(3,331)	(3,231)
Net loss attributable to common stockholders		$ (104,255)	$ (92,438)	$ (100,245)
Loss per share basic and diluted:
Net loss per share attributable to common stockholders, basic		$ (0.31)	$ (0.42)	$ (1.82)
Net loss per share attributable to common stockholders, diluted	[1]	$ (0.31)	$ (0.42)	$ (1.82)
Basic weighted average shares outstanding		334,742,346	221,960,288	55,081,266
Diluted weighted average shares outstanding		334,742,346	221,960,288	55,081,266
Series A Warrant
Operating expenses:
Change in fair value of common stock warrant liability				$ 3,169
Series B Preferred Stock
Operating expenses:
Series B preferred stock dividends		$ (3,200)	$ (3,331)	(3,231)
Series C Preferred Stock
Operating expenses:
Series C preferred stock deemed dividends and redemption value adjustment, net				(6,522)
Series D Preferred Stock
Operating expenses:
Series D preferred stock deemed dividends and redemption accretion				(9,755)
Product
Revenues:
Revenues				481
Costs of revenues:
Costs of revenues		7,976	9,924	18,552
Service and License
Revenues:
Revenues		19,791	25,133	26,618
Costs of revenues:
Costs of revenues		24,735	24,545	18,943
Generation
Revenues:
Revenues		24,027	19,943	14,034
Costs of revenues:
Costs of revenues		36,017	27,873	31,642
Advanced Technologies
Revenues:
Revenues		25,767	25,795	19,619
Costs of revenues:
Costs of revenues		$ 16,496	$ 16,254	$ 12,884

[1] Due to the net loss to common stockholders in each of the years presented above, diluted earnings per share was computed without consideration to potentially dilutive instruments as their inclusion would have been antidilutive.