Schedule of prepayments and other receivables (Details) - EUR (€) € in Thousands	Jun. 30, 2026	Dec. 31, 2025
Notes and other explanatory information [abstract]
Trade receivables	€ 5,099	€ 4,774
Contract fulfilment asset	979
Prepayments	26	27
VAT recoverable	135	17
Loan receivable	170
Other receivables	247	229
Total prepayments and other receivables	€ 6,656	€ 5,047

Contract fulfilment asset.

No definition available.

Name:	HTOO_ContractFulfilmentAsset
Namespace Prefix:	HTOO_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Loan receivable.

+ References

No definition available.

+ Details

Name:	HTOO_LoanReceivable
Namespace Prefix:	HTOO_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of current prepayments. [Refer: Prepayments]

+ References

+ Details

Name:	ifrs-full_CurrentPrepayments
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of current prepayments and other current assets. [Refer: Other current assets; Current prepayments]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Note Expiry date 2027-01-01
-Name IAS
-Number 1
-IssueDate 2025-01-01
-Paragraph 55
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2025-en-b&anchor=para_55&doctype=Standard
-URIDate 2025-03-27

+ Details

Name:	ifrs-full_CurrentPrepaymentsAndOtherCurrentAssets
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of current trade receivables. [Refer: Trade receivables]

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Note Effective 2027-01-01
-Name IFRS
-Number 19
-IssueDate 2025-01-01
-Paragraph B9
-Subparagraph b
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=19&code=ifrs-tx-2025-en-r&anchor=para_B9_b&doctype=Appendix&subtype=B
-URIDate 2025-03-27

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Note Expiry date 2027-01-01
-Name IAS
-Number 1
-IssueDate 2025-01-01
-Paragraph 68
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2025-en-b&anchor=para_68&doctype=Standard
-URIDate 2025-03-27

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Note Expiry date 2027-01-01
-Name IAS
-Number 1
-IssueDate 2025-01-01
-Paragraph 78
-Subparagraph b
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2025-en-b&anchor=para_78_b&doctype=Standard
-URIDate 2025-03-27

+ Details

Name:	ifrs-full_CurrentTradeReceivables
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of current value added tax receivables. [Refer: Value added tax receivables]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Note Expiry date 2027-01-01
-Name IAS
-Number 1
-IssueDate 2025-01-01
-Paragraph 78
-Subparagraph b
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2025-en-b&anchor=para_78_b&doctype=Standard
-URIDate 2025-03-27

+ Details

Name:	ifrs-full_CurrentValueAddedTaxReceivables
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

Name:	ifrs-full_NotesAndOtherExplanatoryInformationAbstract
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of current other receivables. [Refer: Other receivables]

+ References

+ Details

Name:	ifrs-full_OtherCurrentReceivables
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant