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Accounts Receivable, Contract Assets and Contract Liabilities (Tables) | 3 Months Ended
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Jul. 31, 2025
Accounts Receivable Contract Assets And Contract Liabilities |
Schedule of Accounts Receivable, Contract Assets and Contract Liabilities | The following provides further details on the balance sheet accounts of accounts receivable, contract assets and contract liabilities from contracts with customers: Schedule of Accounts Receivable, Contract Assets and Contract Liabilities
|  | July 31, 2025 |  |  | April 30, 2025 |  |  | April 30, 2024 |
|  | (in thousands) |
Accounts receivable |  | $ | 2,207 |  |  | $ | 1,191 |  |  | $ | 796 |
Contract assets |  | $ | 555 |  |  | $ | 1,088 |  |  | $ | 18 |
Contract liabilities |  | $ | 135 |  |  | $ | — |  |  | $ | 302 |
Schedule of Significant Changes in Contract Assets | Significant changes in the contract assets balances during the period were as follows: Schedule of Significant Changes in Contract Assets
|  | Three months ended July 31, 2025 |  |  | Three months ended July 31, 2024 |
|  | (in thousands) |
Transferred to receivables from contract assets recognized |  | $ | (644 | ) |  | $ | (104 | )
Revenue recognized and not billed |  |  | 111 |  |  |  | 563 |
Net change in contract assets |  | $ | (533 | ) |  | $ | 459 |
Schedule of Significant Changes in Contract Liabilities | Significant changes in the contract liabilities balances during the period are as follows: Schedule of Significant Changes in Contract Liabilities
|  | Three months ended July 31, 2025 |  |  | Three months ended July 31, 2024 |
|  | (in thousands) |
Revenue recognized |  | $ | (115 | ) |  | $ | (545 | )
Payments collected for which revenue has not been recognized |  |  | 250 |  |  |  | 689 |
Net change in contract liabilities |  | $ | 135 |  |  | $ | 144 |

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- Definition Contract With Customer Asset [Table Text Block] + References No definition available. + Details
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Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

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- Definition Contract With Customer Liabilities [Table Text Block] + References No definition available. + Details
Name: | OPTT_ContractWithCustomerLiabilitiesTableTextBlock
Namespace Prefix: | OPTT_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

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- References No definition available. + Details
Name: | OPTT_DisclosureAccountsReceivableContractAssetsAndContractLiabilitiesAbstract
Namespace Prefix: | OPTT_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Schedule of accounts receivable contract assets and contract liabilities [Table Text Block] + References No definition available. + Details
Name: | OPTT_ScheduleOfAccountsReceivableContractAssetsAndContractLiabilitiesTableTextBlock
Namespace Prefix: | OPTT_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration