Julián Martínez-Simancas Secretary of the Board of Directors

Bilbao, 21 May 2021 To the National Securities Market Commission

Subject: Other relevant information / periodic information about the share buy­back programme of , S.A.

Reference is made to our notice of other relevant information of 11 May 2021 (official registry number 9,361), relating to the buy­back programme of own shares approved by the Board of Directors of Iberdrola, S.A. (the “Company”) in accordance with the authorisation granted by the General Shareholders’ Meeting held on 13 April 2018 under item twelve of its agenda (the “Buy­back Programme”).

Pursuant to article 227 of the restated text of the Securities Market Law approved by the Royal Legislative Decree 4/2015, of 23 October (texto refundido de la Ley del Mercado de Valores aprobado por el Real Decreto Legislativo 4/2015, de 23 de octubre) and related provisions, and in accordance with articles 2.2 and 2.3 of Commission Delegated Regulation (EU) 2016/1052 of 8 March 2016 supplementing Regulation (EU) No 596/2014 of the European Parliament and of the Council with regard to regulatory technical standards for the conditions applicable to buy-back programmes and stabilisation measures, we hereby inform you that between 12 and 20 May 2021, the Company has carried out the following transactions over its own shares under the Buy-back Programme:

Date Security Transaction Trading venue Number of securities Price (€) 12/05/2021 IBE.MC Acquisition XMAD 2,450,215 11.190 12/05/2021 IBE.MC Acquisition CEUX 720,068 11.197 12/05/2021 IBE.MC Acquisition TRQX 296,052 11.193 13/05/2021 IBE.MC Acquisition XMAD 110,970 10.922 13/05/2021 IBE.MC Acquisition CEUX 102,500 10.933 13/05/2021 IBE.MC Acquisition TRQX 70,276 10.932 13/05/2021 IBE.MC Acquisition AQXE 23,356 10.937 18/05/2021 IBE.MC Acquisition XMAD 450,000 11.320

Detailed information of all the transactions carried out within the referred period is attached as annex.

This information is provided to you for the appropriate purposes.

Secretary of the Board of Directors

NOTICE: This document is a translation of a duly approved Spanish-language document, and is provided for informational purposes only. In the event of any discrepancy between the text of this translation and the text of the original Spanish-language document which this translation is intended to reflect, the text of the original Spanish-language document shall prevail. www.iberdrola.com

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ANNEX Detailed information of all the transactions carried out under the Buy­back Programme between 12 and 20 May 2021

Trading Number of Date Security Transaction Price (€) Broker venue securities 12/05/2021 IBE.MC Acquisition XMAD 13,277 11.105 S.A. 12/05/2021 IBE.MC Acquisition XMAD 21,049 11.110 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition XMAD 2,928 11.115 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition XMAD 44,721 11.120 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition XMAD 13,622 11.125 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition XMAD 9,170 11.130 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition XMAD 16,335 11.135 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition XMAD 29,645 11.140 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition XMAD 30,200 11.145 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition XMAD 62,946 11.150 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition XMAD 98,637 11.155 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition XMAD 107,049 11.160 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition XMAD 261,154 11.165 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition XMAD 159,816 11.170 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition XMAD 100,949 11.175 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition XMAD 161,658 11.180 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition XMAD 100,003 11.185 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition XMAD 96,418 11.190 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition XMAD 93,417 11.195 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition XMAD 54,630 11.200 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition XMAD 136,964 11.205 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition XMAD 99,501 11.210 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition XMAD 51,136 11.215 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition XMAD 183,641 11.220 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition XMAD 129,708 11.225 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition XMAD 119,923 11.230 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition XMAD 67,761 11.235 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition XMAD 105,318 11.240 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition XMAD 21,457 11.245 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition XMAD 43,864 11.250 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition XMAD 3,411 11.255 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition XMAD 3,281 11.260 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition XMAD 1,681 11.265 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition XMAD 4,945 11.270 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition CEUX 9,427 11.105 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition CEUX 13,264 11.110 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition CEUX 6,727 11.115 Banco Santander S.A.

NOTICE: This document is a translation of a duly approved Spanish-language document, and is provided for informational purposes only. In the event of any discrepancy between the text of this translation and the text of the original Spanish-language document which this translation is intended to reflect, the text of the original Spanish-language document shall prevail. www.iberdrola.com

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Trading Number of Date Security Transaction Price (€) Broker venue securities 12/05/2021 IBE.MC Acquisition CEUX 18,520 11.120 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition CEUX 3,304 11.125 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition CEUX 5,500 11.130 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition CEUX 9,961 11.135 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition CEUX 11,102 11.140 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition CEUX 5,068 11.145 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition CEUX 14,033 11.150 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition CEUX 11,973 11.155 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition CEUX 26,973 11.160 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition CEUX 16,788 11.165 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition CEUX 30,196 11.170 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition CEUX 26,404 11.175 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition CEUX 51,151 11.180 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition CEUX 32,327 11.185 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition CEUX 16,356 11.190 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition CEUX 47,369 11.195 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition CEUX 27,239 11.200 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition CEUX 20,918 11.205 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition CEUX 11,592 11.210 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition CEUX 24,132 11.215 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition CEUX 27,140 11.220 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition CEUX 17,861 11.225 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition CEUX 40,917 11.230 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition CEUX 65,642 11.235 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition CEUX 64,694 11.240 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition CEUX 36,222 11.245 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition CEUX 22,172 11.250 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition CEUX 5,096 11.255 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition TRQX 5,432 11.105 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition TRQX 303 11.115 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition TRQX 1,743 11.125 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition TRQX 1,617 11.130 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition TRQX 10,655 11.135 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition TRQX 2,539 11.140 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition TRQX 14,279 11.145 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition TRQX 10,186 11.150 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition TRQX 2,886 11.155 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition TRQX 7,253 11.160 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition TRQX 14,794 11.165 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition TRQX 3,583 11.170 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition TRQX 10,280 11.175 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition TRQX 21,916 11.180 Banco Santander S.A.

NOTICE: This document is a translation of a duly approved Spanish-language document, and is provided for informational purposes only. In the event of any discrepancy between the text of this translation and the text of the original Spanish-language document which this translation is intended to reflect, the text of the original Spanish-language document shall prevail. www.iberdrola.com

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Trading Number of Date Security Transaction Price (€) Broker venue securities 12/05/2021 IBE.MC Acquisition TRQX 23,816 11.185 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition TRQX 10,499 11.190 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition TRQX 14,057 11.195 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition TRQX 8,559 11.200 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition TRQX 24,085 11.205 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition TRQX 18,002 11.210 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition TRQX 16,015 11.215 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition TRQX 14,407 11.220 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition TRQX 11,441 11.225 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition TRQX 12,601 11.230 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition TRQX 10,226 11.235 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition TRQX 8,272 11.240 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition TRQX 6,552 11.245 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition TRQX 8,060 11.250 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition TRQX 1,790 11.255 Banco Santander S.A. 12/05/2021 IBE.MC Acquisition TRQX 204 11.260 Banco Santander S.A. 13/05/2021 IBE.MC Acquisition XMAD 40,000 10.910 JB Capital Markets S.V., S.A. 13/05/2021 IBE.MC Acquisition XMAD 30,000 10.920 JB Capital Markets S.V., S.A. 13/05/2021 IBE.MC Acquisition XMAD 30,000 10.930 JB Capital Markets S.V., S.A. 13/05/2021 IBE.MC Acquisition XMAD 10,970 10.945 JB Capital Markets S.V., S.A. 13/05/2021 IBE.MC Acquisition CEUX 5,000 10.910 JB Capital Markets S.V., S.A. 13/05/2021 IBE.MC Acquisition CEUX 7,641 10.920 JB Capital Markets S.V., S.A. 13/05/2021 IBE.MC Acquisition CEUX 22,359 10.925 JB Capital Markets S.V., S.A. 13/05/2021 IBE.MC Acquisition CEUX 20,000 10.930 JB Capital Markets S.V., S.A. 13/05/2021 IBE.MC Acquisition CEUX 40,000 10.940 JB Capital Markets S.V., S.A. 13/05/2021 IBE.MC Acquisition CEUX 2,500 10.945 JB Capital Markets S.V., S.A. 13/05/2021 IBE.MC Acquisition CEUX 5,000 10.960 JB Capital Markets S.V., S.A. 13/05/2021 IBE.MC Acquisition TRQX 4,000 10.910 JB Capital Markets S.V., S.A. 13/05/2021 IBE.MC Acquisition TRQX 6,174 10.915 JB Capital Markets S.V., S.A. 13/05/2021 IBE.MC Acquisition TRQX 17,232 10.920 JB Capital Markets S.V., S.A. 13/05/2021 IBE.MC Acquisition TRQX 6,174 10.925 JB Capital Markets S.V., S.A. 13/05/2021 IBE.MC Acquisition TRQX 6,174 10.930 JB Capital Markets S.V., S.A. 13/05/2021 IBE.MC Acquisition TRQX 18,348 10.940 JB Capital Markets S.V., S.A. 13/05/2021 IBE.MC Acquisition TRQX 2,058 10.945 JB Capital Markets S.V., S.A. 13/05/2021 IBE.MC Acquisition TRQX 1,000 10.955 JB Capital Markets S.V., S.A. 13/05/2021 IBE.MC Acquisition TRQX 9,116 10.960 JB Capital Markets S.V., S.A. 13/05/2021 IBE.MC Acquisition AQXE 742 10.905 JB Capital Markets S.V., S.A. 13/05/2021 IBE.MC Acquisition AQXE 742 10.910 JB Capital Markets S.V., S.A. 13/05/2021 IBE.MC Acquisition AQXE 1,242 10.915 JB Capital Markets S.V., S.A. 13/05/2021 IBE.MC Acquisition AQXE 1,655 10.920 JB Capital Markets S.V., S.A. 13/05/2021 IBE.MC Acquisition AQXE 1,242 10.925 JB Capital Markets S.V., S.A. 13/05/2021 IBE.MC Acquisition AQXE 3,297 10.930 JB Capital Markets S.V., S.A.

NOTICE: This document is a translation of a duly approved Spanish-language document, and is provided for informational purposes only. In the event of any discrepancy between the text of this translation and the text of the original Spanish-language document which this translation is intended to reflect, the text of the original Spanish-language document shall prevail. www.iberdrola.com

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Trading Number of Date Security Transaction Price (€) Broker venue securities 13/05/2021 IBE.MC Acquisition AQXE 742 10.935 JB Capital Markets S.V., S.A. 13/05/2021 IBE.MC Acquisition AQXE 7,952 10.940 JB Capital Markets S.V., S.A. 13/05/2021 IBE.MC Acquisition AQXE 742 10.945 JB Capital Markets S.V., S.A. 13/05/2021 IBE.MC Acquisition AQXE 5,000 10.960 JB Capital Markets S.V., S.A. 13/05/2021 IBE.MC Acquisition XMAD 525 11.260 CM Capital Markets Bolsa, S.V., S.A. 13/05/2021 IBE.MC Acquisition XMAD 34,497 11.265 CM Capital Markets Bolsa, S.V., S.A. 13/05/2021 IBE.MC Acquisition XMAD 10,336 11.270 CM Capital Markets Bolsa, S.V., S.A. 13/05/2021 IBE.MC Acquisition XMAD 15,000 11.275 CM Capital Markets Bolsa, S.V., S.A. 13/05/2021 IBE.MC Acquisition XMAD 5,000 11.305 CM Capital Markets Bolsa, S.V., S.A. 13/05/2021 IBE.MC Acquisition XMAD 102,844 11.310 CM Capital Markets Bolsa, S.V., S.A. 13/05/2021 IBE.MC Acquisition XMAD 20,503 11.320 CM Capital Markets Bolsa, S.V., S.A. 13/05/2021 IBE.MC Acquisition XMAD 24,664 11.325 CM Capital Markets Bolsa, S.V., S.A. 13/05/2021 IBE.MC Acquisition XMAD 36,631 11.330 CM Capital Markets Bolsa, S.V., S.A. 13/05/2021 IBE.MC Acquisition XMAD 65,000 11.335 CM Capital Markets Bolsa, S.V., S.A. 13/05/2021 IBE.MC Acquisition XMAD 110,000 11.340 CM Capital Markets Bolsa, S.V., S.A. 13/05/2021 IBE.MC Acquisition XMAD 20,000 11.345 CM Capital Markets Bolsa, S.V., S.A. 13/05/2021 IBE.MC Acquisition XMAD 5,000 11.350 CM Capital Markets Bolsa, S.V., S.A.

NOTICE: This document is a translation of a duly approved Spanish-language document, and is provided for informational purposes only. In the event of any discrepancy between the text of this translation and the text of the original Spanish-language document which this translation is intended to reflect, the text of the original Spanish-language document shall prevail. www.iberdrola.com

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IMPORTANT INFORMATION This communication does not constitute an offer to purchase, sell or exchange or the solicitation of an offer to purchase, sell or exchange any securities. The shares of Iberdrola, S.A. may not be offered or sold in the of America except pursuant to an effective registration statement under the Securities Act or pursuant to a valid exemption from registration.

NOTICE: This document is a translation of a duly approved Spanish-language document, and is provided for informational purposes only. In the event of any discrepancy between the text of this translation and the text of the original Spanish-language document which this translation is intended to reflect, the text of the original Spanish-language document shall prevail. www.iberdrola.com

Take care of the environment. Printed in black and white and only if necessary