Commitments and Contingencies	12 Months Ended
Apr. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	(16) Commitments and Contingencies Employment Litigation On June 10, 2014, the Company announced that it had terminated Charles Dunleavy as its Chief Executive Officer and as an employee of the Company for cause, effective June 9, 2014, and that Mr. Dunleavy had also been removed from his position as Chairman of the Board of Directors. On June 17, 2014, Mr. Dunleavy wrote to the Company stating that he had retained counsel to represent him in connection with an alleged wrongful termination of his employment. On July 28, 2014, Mr. Dunleavy resigned from the Board and the boards of directors of the Company’s subsidiaries. On August 28, 2018, counsel for Mr. Dunleavy filed a demand for arbitration, captioned Charles F. Dunleavy v. Ocean Power Technologies, Inc., Case No. 01-18-0003-2374, before the American Arbitration Association in New Jersey. The demand named Ocean Power Technologies, Inc. as the respondent and alleged various claims and sought declaratory relief and permanent injunction. The demand sought damages in the amount of $5.0 million for compensatory and punitive damages, plus interest and attorneys’ fees as well as certain equitable relief. On November 8, 2018, the Company through counsel responded to the demand for arbitration, denied all allegations, and asserted various affirmative defenses. The final day of hearing occurred in Princeton, New Jersey on July 15, 2020. Post-hearing briefs were filed on September 22, 2020. Following those filings, the panel issued two interim awards finding, among other things, that the termination for cause of Mr. Dunleavy was in breach of his employment contract and awarding him compensatory damages in the amount of $438,255. The panel denied Mr. Dunleavy’s claims for defamation and injunctive and declaratory relief. The panel also awarded Mr. Dunleavy attorneys’ fees, costs and pre-judgment interest. The Company agreed, on May 24, 2021, to pay Mr. Dunleavy $1,223,963, representing the total compensatory damages, attorneys’ fees, costs and pre-judgment interest, which is the full amount awarded by the panel. This was paid in full on May 26, 2021 and the matter is now closed. This amount has been accrued in the April 30, 2021 financial statements. Spain Income Tax Audit The Company underwent an income tax audit in Spain for the period from 2011 to 2014, when our Spanish branch was closed. In connection with the tax audit, the Spanish tax inspector challenged the Company’s recognition of grant funds received in 2011 to 2014 from the European Commission in connection with the Company’s Waveport project. On July 30, 2018, the inspector concluded that although there was no tax owed in light of losses reported, the Company’s Spanish branch owed penalties for failure to properly account for the income associated with the funding grant. On August 30, 2018, the Company filed an administrative appeal of the penalty and its underlying conclusions. During the three months ended July 31, 2020, the Company received notice from the Spanish Central Economic and Administrative Tribunal that it agreed with the inspector and ruled that the Company owes the full amount of the penalty in the amount of €279,870 or approximately $331,000. In the quarter ended October 31, 2020, the Company recorded an additional reserve of €117,146 (or approximately $154,000) to Selling, general and administrative costs in the Statement of Operations making the total reserve €279,870, which amount was paid by the Company to the Spanish Tax Administration on January 25, 2021. As of April 30, 2021, and 2020, the Company has reserved zero and €162,724 (or approximately $177,000), respectively. The penalty was recorded in Accrued expenses in the Consolidated Balance Sheets. The Company has appealed the decision of the Tribunal tax assessment to the Spanish National Court.

Commitments and Contingencies

12 Months Ended

Apr. 30, 2021

Commitments and Contingencies Disclosure [Abstract]

(16) Commitments and Contingencies

Employment Litigation

On June 10, 2014, the Company announced that it had terminated Charles Dunleavy as its Chief Executive Officer and as an employee of the Company for cause, effective June 9, 2014, and that Mr. Dunleavy had also been removed from his position as Chairman of the Board of Directors. On June 17, 2014, Mr. Dunleavy wrote to the Company stating that he had retained counsel to represent him in connection with an alleged wrongful termination of his employment. On July 28, 2014, Mr. Dunleavy resigned from the Board and the boards of directors of the Company’s subsidiaries. On August 28, 2018, counsel for Mr. Dunleavy filed a demand for arbitration, captioned Charles F. Dunleavy v. Ocean Power Technologies, Inc., Case No. 01-18-0003-2374, before the American Arbitration Association in New Jersey. The demand named Ocean Power Technologies, Inc. as the respondent and alleged various claims and sought declaratory relief and permanent injunction. The demand sought damages in the amount of $5.0 million for compensatory and punitive damages, plus interest and attorneys’ fees as well as certain equitable relief. On November 8, 2018, the Company through counsel responded to the demand for arbitration, denied all allegations, and asserted various affirmative defenses. The final day of hearing occurred in Princeton, New Jersey on July 15, 2020. Post-hearing briefs were filed on September 22, 2020. Following those filings, the panel issued two interim awards finding, among other things, that the termination for cause of Mr. Dunleavy was in breach of his employment contract and awarding him compensatory damages in the amount of $438,255. The panel denied Mr. Dunleavy’s claims for defamation and injunctive and declaratory relief. The panel also awarded Mr. Dunleavy attorneys’ fees, costs and pre-judgment interest. The Company agreed, on May 24, 2021, to pay Mr. Dunleavy $1,223,963, representing the total compensatory damages, attorneys’ fees, costs and pre-judgment interest, which is the full amount awarded by the panel. This was paid in full on May 26, 2021 and the matter is now closed. This amount has been accrued in the April 30, 2021 financial statements.

Spain Income Tax Audit

The Company underwent an income tax audit in Spain for the period from 2011 to 2014, when our Spanish branch was closed. In connection with the tax audit, the Spanish tax inspector challenged the Company’s recognition of grant funds received in 2011 to 2014 from the European Commission in connection with the Company’s Waveport project. On July 30, 2018, the inspector concluded that although there was no tax owed in light of losses reported, the Company’s Spanish branch owed penalties for failure to properly account for the income associated with the funding grant. On August 30, 2018, the Company filed an administrative appeal of the penalty and its underlying conclusions. During the three months ended July 31, 2020, the Company received notice from the Spanish Central Economic and Administrative Tribunal that it agreed with the inspector and ruled that the Company owes the full amount of the penalty in the amount of €279,870 or approximately $331,000. In the quarter ended October 31, 2020, the Company recorded an additional reserve of €117,146 (or approximately $154,000) to Selling, general and administrative costs in the Statement of Operations making the total reserve €279,870, which amount was paid by the Company to the Spanish Tax Administration on January 25, 2021. As of April 30, 2021, and 2020, the Company has reserved zero and €162,724 (or approximately $177,000), respectively. The penalty was recorded in Accrued expenses in the Consolidated Balance Sheets. The Company has appealed the decision of the Tribunal tax assessment to the Spanish National Court.