Report of Foreign Issuer Pursuant to Rule 13a-16 or 15d-16 (6-k)

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 6-K

REPORT OF FOREIGN PRIVATE ISSUER

PURSUANT TO RULE 13a-16 OR 15d-16

UNDER THE SECURITIES EXCHANGE ACT OF 1934

For the month of May, 2021

Commission File Number 001-36487

Atlantica Sustainable Infrastructure plc

(Exact name of Registrant as specified in its charter)

Not applicable

(Translation of Registrant’s name into English)

Great West House, GW1, 17th floor

Great West Road

Brentford, TW8 9DF

United Kingdom

Tel: +44 203 499 0465

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F:

☒ Form 20-F

☐ Form 40-F

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(1): ☐

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(7): ☐

This Report on Form 6-K is incorporated by reference into the Registration Statement on Form F-3 of the Registrant filed with the Securities and Exchange Commission on August 6, 2018 (File 333-226611).

Q1 2021 Earnings Presentation May 6, 2021

DISCLAIMER Forward Looking StatementsThis presentation contains forward-looking statements. These forward-looking statements include, but are not limited to, all statements other than statements of historical facts contained in this presentation, including, without limitation, those regarding our future financial position and results of operations, our strategy, plans, objectives, goals and targets, future developments in the markets in which we operate or are seeking to operate or anticipated regulatory changes in the markets in which we operate or intend to operate. In some cases, you can identify forward-looking statements by terminology such as "aim," "anticipate," "believe," "continue," "could," "estimate," "expect," "forecast," "guidance," "intend," "is likely to," "may," "plan," "potential," "predict," "projected," "should" or "will" or the negative of such terms or other similar expressions or terminology.By their nature, forward-looking statements involve risks and uncertainties because they relate to events and depend on circumstances that may or may not occur in the future. Forward-looking statements speak only as of the date of this presentation and are not guarantees of future performance and are based on numerous assumptions. Our actual results of operations, financial condition and the development of events may differ materially from (and be more negative than) those made in, or suggested by, the forward-looking statements. Except as required by law, we do not undertake any obligation to update any forward-looking statements to reflect events or circumstances after the date hereof or to reflect the occurrence of anticipated or unanticipated events or circumstances.Investors should read the section entitled "Item 3.D—Risk Factors" and the description of our segments and business sectors in the section entitled "Item 4B. Information on the Company—Business Overview", each in our Annual Report for the fiscal year ended December 31, 2020, filed on Form 20-F, for a more complete discussion of the risks and factors that could affect us.Forward-looking statements include, but are not limited to, statements relating to: expected value, payments and closing timelines for investments; business synergies from investments; equity investment and project growth strategy; accretive investment opportunities; strategic business alternatives to ensure optimal company value; estimated returns and cash available for distribution (“CAFD”) estimates, including CAFD per share growth strategy and targets, CAFD estimates per currency, geography and sector, including as a result of project debt refinancing; net corporate leverage based on CAFD estimates; debt refinancing; the quality of our long-term contracts; self-amortizing project debt structure and related debt reduction; the use of non-GAAP measures as a useful predicting tool for investors; the possibility to extend asset life; cost improvements from debt refinancing; dividends; and various other factors, including those factors discussed under “Item 3.D—Risk Factors” and “Item 5.A—Operating Results” in our Annual Report for the fiscal year ended December 31, 2020 filed on Form 20-F.The CAFD and other guidance incorporated into this presentation are estimates as of March 1, 2021. These estimates are based on assumptions believed to be reasonable as of the date Atlantica published its 2020 Financial Results. Atlantica disclaims any current intention to update such guidance, except as required by law. Non-GAAP Financial Information This presentation also includes certain non-GAAP financial measures, including Adjusted EBITDA including unconsolidated affiliates, Adjusted EBITDA including unconsolidated affiliates as a percentage of revenues (margin) and CAFD. Non-GAAP financial measures are not measurements of our performance or liquidity under IFRS as issued by IASB and should not be considered alternatives to operating profit or profit for the period or any other performance measures derived in accordance with IFRS as issued by the IASB or any other generally accepted accounting principles or as alternatives to cash flow from operating, investing or financing activities. Please refer to the appendix of this presentation for a reconciliation of the non-GAAP financial measures included in this presentation to the most directly comparable financial measures prepared in accordance with IFRS as well as the reasons why management believes the use of non-GAAP financial measures (including CAFD and Adjusted EBITDA) in this presentation provides useful information to investors.In our discussion of operating results, we have included foreign exchange impacts in our revenue and Adjusted EBITDA including unconsolidated affiliates by providing constant currency growth. The constant currency presentation is not a measure recognized under IFRS and excludes the impact of fluctuations in foreign currency exchange rates. We believe providing constant currency information provides valuable supplemental information regarding our results of operations. We calculate constant currency amounts by converting our current period local currency revenue and Adjusted EBITDA using the prior period foreign currency average exchange rates and comparing these adjusted amounts to our prior period reported results. This calculation may differ from similarly titled measures used by others and, accordingly, the constant currency presentation is not meant to substitute for recorded amounts presented in conformity with IFRS as issued by the IASB nor should such amounts be considered in isolation.

Key Messages Q1 2021 dividend of $0.43 per share New investment announced: a 49% interest in a 596 MW Wind Portfolio in the US for approx. $196.5 million2 +7.6% year-over-year CAFD growth in Q1 2021 up to $51.2 million Adjusted EBITDA including unconsolidated affiliates includes our share in EBITDA of unconsolidated affiliates (see reconciliation on page 24).Subject to certain customary adjustments. Closed two previously announced investments:Coso, a 135MW contracted renewable energy plant in CaliforniaChile PV2, a 40MW solar plant in Chile, through our investment platform +11.8% year-over-year Revenue growth in Q1 2021 up to $235.2 million and +2.5% Adj. EBITDA incl. unconsolidated affiliates1 growth up to $170.1 million

US $ in millions 2021 2020 ∆ Reported Revenue 235.2 210.4 +11.8% Adjusted EBITDA incl. unconsolidated affiliates1 170.1 166.0 +2.5% Margin2 72% 79% CAFD 51.2 47.6 +7.6% First Quarter HIGHLIGHTS7.6% CAFD Growth in Q1 2021 Adjusted EBITDA including unconsolidated affiliates includes our share in EBITDA of unconsolidated affiliates (see reconciliation on page 24).Adjusted EBITDA Margin including unconsolidated affiliates is defined as Adjusted EBITDA including unconsolidated affiliates divided by revenue (see reconciliation on page 26).

Adjusted EBITDA including unconsolidated affiliates includes our share in EBITDA of unconsolidated affiliates (see reconciliation on page 24).Adjusted EBITDA Margin including unconsolidated affiliates is defined as Adjusted EBITDA including unconsolidated affiliates divided by revenue (see reconciliation on page 26). HIGHLIGHTSPerformance by Sector and Region WATER Q1 2021 Q1 2020 ∆ 13.5 6.6 +105% 9.8 5.9 +66% 73% 90% RENEWABLES Q1 2021 Q1 2020 ∆ 166.7 150.8 11% 115.9 113.7 2% 70% 75% EFFICIENT NATURAL GAS Q1 2021 Q1 2020 ∆ 28.4 26.4 +8% 23.2 24.5 (5)% 82% 93% TRANSMISSION Q1 2021 Q1 2020 ∆ 26.6 26.6 +0% 21.2 21.9 (3)% 80% 82% By Sector US $ in millions Revenue Adjusted EBITDA incl. unconsolidated affiliates1 Margin2 EMEA NORTH AMERICA Q1 2021 Q1 2020 ∆ 60.6 59.3 +2% 40.3 52.7 (24)% 67% 89% SOUTH AMERICA Q1 2021 Q1 2020 ∆ 136.3 115.5 +18% 99.8 84.9 +18% 73% 74% By Region US $ in millions Revenue Adjusted EBITDA incl. unconsolidated affiliates1 Margin2 Q1 2021 Q1 2020 ∆ 38.3 35.7 +7% 30.0 28.4 +6% 78% 80%

Includes curtailment in wind assets for which we receive compensation.Represents total installed capacity in assets owned or consolidated for the first quarter of 2021 and 2020, regardless of our percentage of ownership in each of the assets.GWh produced includes 30% of the production from Monterrey.Availability refers to the time during which the asset was available to our client totally or partially divided by contracted or budgeted availability, as applicable.Includes 43 MW corresponding to our 30% share in Monterrey. WATER RENEWABLES TRANSMISSION & TRANSPORTATION EFFICIENT NATURAL GAS Q1 2021 Q1 2020 Availability4 97.5% 101.8% Mft3 in operation2 17.5 10.5 Q1 2021 Q1 2020 GWh produced1 606 526 MW in operation2 1,591 1,496 Q1 2021 Q1 2020 GWh produced3 542 644 Availability4 98.3% 102.4% MW in operation5 343 343 Q1 2021 Q1 2020 Availability4 100.0% 99.9% Miles in operation 1,166 1,166 KEY OPERATIONAL METRICSSteady Operational Performance

Adjusted EBITDA including unconsolidated affiliates includes our share in EBITDA of unconsolidated affiliates (see reconciliation on page 24).Consolidated cash as of March 31, 2021 increased by $190.3 million vs December 31, 2020 including FX translation differences of $(9.1) million. US $ in millions 2021 2020 Adjusted EBITDA incl. unconsolidated affiliates1 170.1 166.0 Share in Adjusted EBITDA of unconsolidated affiliates (3.3) (3.6) Net interest and income tax paid (30.7) (11.4) Variations in working capital 17.0 (59.3) Non-monetary adjustments and other (6.4) (6.0) OPERATING CASH FLOW 146.7 85.7 INVESTING CASH FLOW (6.3) (0.8) FINANCING CASH FLOW 59.1 59.8 Net change in consolidated cash2 199.5 144.7 CASH FLOWOperating Cash Flow First Quarter

NET DEBT POSITION1 Net debt corresponds to gross debt including accrued interest less cash and cash equivalents.Corporate Net Debt defined as indebtedness where Atlantica Sustainable Infrastructure plc. is the primary obligor minus cash and cash equivalents held at Atlantica Sustainable Infrastructure plc. Project Net Debt is defined as indebtedness where one of our project subsidiaries is the primary obligor minus cash and cash equivalents held by our project subsidiaries.Net corporate leverage is calculated as corporate net debt divided by midpoint 2021 CAFD guidance before corporate debt service. For net corporate leverage ratio calculation purposes, corporate net debt as of March 31, 2021, has been calculated to include $130M equity investment paid in April 2021 and $40M of project debt pre-payment expected to occur in July 2021. As a result, net corporate debt increased by $170M to $701M. CAFD has not been changed. Absent such adjustment to corporate cash and net corporate debt, the ratio of corporate net debt / CAFD pre-corporate debt service was 2.0x. US $ in millions As of Mar. 31,2021 As of Dec. 31,2020 Corporate Net Debt2 531.1 658.5 Project Net Debt3 4,575.6 4,704.3 NET DEBTCorporate Leverage Corporate net debt / CAFD pre corporate debt service, including impact of Coso investment4 2.6x

NEW INVESTMENTA 596 MW Wind Portfolio in the US 4 wind assets in Illinois, Texas, Oregon and Minnesota ~$197 million investment1 Proven track recordClosing expected in Q3 2021 Increases and diversifies presence in North AmericaIncreases presence in renewablesFully contracted revenues with PPAs with investment grade offtakers Acquisition of a 49% interest in a 596 MW Wind Portfolio in the US INVESTMENT HIGHLIGHTS ~5.9x EV2 / EBITDA3 No project debt as of todaySubstantial value post PPA, including repowering opportunities Subject to certain customary adjustments.(2) Entreprise Value is defined as the expected investment divided by the 49% equity interest agreed to be acquired. The asset has no debt. (3) EBITDA is calculated as profit/(loss) of the portfolio for the year 2020 after adding back depreciation, amortization and impairment charges. There were no financing costs or income tax in 2020 in this portfolio (see reconciliation on page 26).

Appendix Q1 2021 Results Presentation

ESG FOCUSStrong ESG Ratings in 2021 Renewable Power Production #1 out of 67 Utilities #1 out of 574 Global Universe #21 out of 13,568 Risk score of 7.6, improved versus 2020“Negligible risk of experiencing material financial impacts” 1 from ESG factors“Strong management of material ESG issues”1 “Leadership: Implementing current best practices”1 #1 Globally in Renewable Power and Utilities (ESG Risk Rating) “A-” Rating 100 Most Sustainable Corporations in the World 12th Globally, 2nd in Power According to Sustainalytics ESG Risk Rating Summary Report dated February 22, 2021 and CDP Score Report - Climate Change 2020. For further information please see both reports on our website. Feb. 2021 Jan. 2021 Jan. 2021

LIQUIDITY AND DEBT MATURITIES SUMMARYHealthy Balance Sheet and Strong Liquidity Strong Liquidity and No Significant Corporate Debt Maturities in the Short-term >$870 million @ 31/03/21 Corporate Liquidity ~4.8 years average maturity2 of current corporate debt RCF’s maturity extended to December 2023 on March 1, 2021. New total limit is $450.0 million, of which $440.0 million are available as of March 31, 2021~$874 million available liquidity, out of which $434.2 million is corporate cash as of Mar. 31, 2021 Corporate Debt Maturities1 Corporate Debt is the indebtedness where Atlantica Sustainable Infrastructure plc. is the primary obligor.Corporate Debt Maturities as of March 31, 2021.Corporate Liquidity means cash and cash equivalents held at Atlantica Sustainable Infrastructure plc as of March 31, 2021 plus available capacity under the Revolving Credit Facility as of March 31, 2021.Corporate Cash corresponds to cash and cash equivalents held at Atlantica Sustainable Infrastructure plc. 2 2 3 4

CORPORATE DEBT DETAILSCorporate Debt as of March 31, 2021No significant maturities in the short term Exchange rates as of March 31, 2021 (EUR/USD = 1.1774).Amounts include principal amounts outstanding, unless stated otherwise.RCF’s maturity was extended to December 31, 2023 on March 1, 2021. As of March 31, 2021, letters of credit with face value in an amount equal to $10 million were outstanding and $440 million were available under the RCF. Total new RCF limit of $450 million.Other facilities include the commercial paper program, accrued interest payable and other debts. US $ in millions1 Maturity Amounts2 Credit Facilities (Revolving CF)3 2023 - (Other facilities)4 2021 – 2025 31.5 2019 NIFA5(€ denominated) 2025 331.9 Green Exchangeable Bond6 2025 102.7 Green Senior Secured Notes7(€ denominated) 2026 338.4 2020 NIFA8 (€ denominated) 2027 160.9 Total 965.3 (5) 2019 NIFA refers to the senior unsecured note facility dated April 30, 2019, of €268 million.Senior unsecured notes dated July 17, 2020, exchangeable into ordinary shares of Atlantica, cash, or a combination of both, at Atlantica’s election.Senior secured notes dated April 1, 2020, of €290 million.(8) 2020 NIFA refers to the senior unsecured note facility dated July 8, 2020, of €140 million.

Exchange rates as of March 31, 2021 (EUR/USD = 1.1774) and December 31, 2020 (EUR/USD = 1.2216).Restricted cash is cash which is restricted generally due to requirements of project finance agreements. US $ in millions1 As of March 312021 As of Dec. 312020 Corporate cash at Atlantica 434.2 335.2 Existing available revolver capacity 440.0 415.0 Total Corporate Liquidity 874.2 750.2 Cash at project companies 624.6 533.3 - Restricted2 310.7 279.8 - Other 313.9 253.5 LIQUIDITYLiquidity Position

Weighted Average Life Project debt term (2) Regulation term in the case of Spain and Chile TL3. PPAs with predefined prices for ~16 years on average1 Refinancing opportunities could increase CAFD in earlier years Possibility to extend life in many assets (excluding ATN and ATS) Tails in most assets after debt amortization Contract term2 LONG-TERM STABLE CASH FLOWPortfolio of Assets Represents weighted average years remaining as of March 31, 2021 including announced acquisitions as of April 7, 2021.

Key principle: non-recourse project financing in ring-fenced subsidiaries100% project debt self-amortizing progressively before the end of the contracted lifeLow interest rate risk, with +90% of interest rates fixed or hedged ~$1.9B planned debt reduction in the next 5 years FINANCING Self-Amortizing Project Debt Structure1 Project debt amortization schedule as of December 31, 2020.

1Q19 2Q19 3Q19 4Q19 2019 1Q20 2Q20 3Q20 4Q20 2020 1Q21 Revenues 221,452 283,338 293,373 213,289 1,011,452 210,403 255,344 302,987 244,526 1,013,260 235,190 Adj. EBITDA incl. unconsolidated affiliates 181,106 229,352 247,668 163,429 821,555 165,962 214,107 240,958 175,096 796,123 170,070 Adj. EBITDA margin (%) 81.8% 80.9% 84.4% 76.6% 81.2% 78.9% 83.9% 79.5% 71.6% 78.6% 72.3% Atlantica’s pro-rata share of EBITDA from unconsolidated affiliates (2,017) (2,043) (3,062) (3,229) (10,351) (3,553) (3,959) (3,943) (3,013) (14,468) (3,298) Adjusted EBITDA 179,089 227,309 244,606 160,200 811,204 162,409 210,148 237,015 172,083 781,655 166,772 Dividends from unconsolidated affiliates - - 26,945 3,498 30,443 5,120 5,262 9,758 2,106 22,246 8,799 Non-monetary items (14,632) (7,729) (10,288) (4,783) (37,432) (4,334) (3,683) (5,327) (8,289) (21,633) (6,177) Net interest and income tax paid (13,925) (129,405) (24,339) (131,845) (299,514) (11,436) (119,517) (31,625) (124,661) (287,239) (30,663) Principal amortization of indebtedness net of new indebtedness at projects (15,176) (93,935) (22,115) (123,568) (254,794) (14,898) (75,301) (18,963) (151,260) (260,422) (22,693) Deposits into/withdrawals from debt service accounts1 21,461 25,564 (52,463) 4,721 (717) 32,921 17,605 8,844 27,807 87,177 (26,576) Change in non-restricted cash at project companies1 (61,445) 69,866 (58,847) 119,707 69,281 (50,467) 31,257 (94,192) 34,784 (78,618) (63,265) Dividends paid to non-controlling interests - (5,105) (18,978) (5,156) (29,239) (4,915) (9,246) (6,833) (1,950) (22,944) (4,215) Changes in other assets and liabilities (50,253) (37,183) (38,792) 27,271 (98,957) (66,842) (6,808) (46,724) 100,843 (19,531) 29,255 Cash Available For Distribution (CAFD) 45,119 49,382 45,729 50,045 190,275 47,558 49,717 51,953 51,463 200,691 51,237 Dividends declared2 39,625 40,641 41,657 41,657 163,579 41,657 42,673 42,673 46,491 173,494 47,643 # of shares3 100,217,260 101,601,662 101,601,662 101,601,662 101,601,662 101,601,662 101,601,662 101,601,662 110,691,722 n/a 110,797,738 DPS (in $ per share) 0.39 0.40 0.41 0.41 1.61 0.41 0.42 0.42 0.42 1.67 0.43 Project debt 5,076.4 4,997.4 4,931.3 4,852.3 4,852.3 4,777.2 5,007.6 5,281.2 5,237.6 5,237.6 5,200.2 Project cash Project cash (546.7) (469.0) (568.5) (496.8) (496.8) (535.3) (510.1) (602.2) (533.3) (533.3) (624.6) Net project debt 4,529.6 4,528.4 4,362.8 4,355.6 4,355.6 4,241.9 4,497.5 4,679.0 4,704.3 4,704.3 4,575.6 Corporate debt 697.5 689.6 686.4 723.8 723.8 807.3 837.0 959.7 993.7 993.7 965.3 Corporate cash (107.9) (107.0) (73.2) (66.0) (66.0) (154.9) (278.7) (186.7) (335.2) (335.2) (434.2) Net corporate debt 589.7 582.6 613.2 657.8 657.8 652.4 558.3 773.0 658.5 658.5 531.1 Total net debt 5.119.3 5,111.0 4,976.0 5,013.3 5,013.3 4,894.4 5,055.8 5,452.0 5,362.9 5,362.8 5,106.7 Net Corporate Debt/CAFD pre corporate interests4 2.5x 2.5x 2.7x 2.9x 2.9x 2.4x 2.3x 3.3x 3.0x 3.0x 2.6x5 HISTORICAL FINANCIAL REVIEWKey Financials by Quarter Debt details Key Financials US $ in thousands “Deposits into/ withdrawals from restricted accounts” and “Change in non-restricted cash at project level” are calculated on a constant currency basis to reflect actual cash movements isolated from the impact of variations generated by foreign exchange changes during the period. Prior periods have been recalculated to conform this presentation.Dividends are paid to shareholders in the quarter after they are declared.Number of shares outstanding on the record date corresponding to each dividend. US $ in millions (4) Ratios presented are the ratios shown on each earnings presentation.(5) For net corporate leverage ratio calculation purposes, corporate net debt as of March 31, 2021, has been calculated proforma including the payment of $170m total investment ($130m equity investment paid in April 2021 plus additional $40m for debt repayment expected in July 2021).

HISTORICAL FINANCIAL REVIEWSegment Financials by Quarter 2 1Q19 2Q19 3Q19 4Q19 2019 1Q20 2Q20 3Q20 4Q20 2020 1Q21 by Geography NORTH AMERICA 60,441 104,095 109,378 59,052 332,965 59,283 98,648 109,757 63,233 330,921 60,585 SOUTH AMERICA 33,493 35,597 36,671 36,447 142,207 35,654 39,375 36,990 39,441 151,460 38,308 EMEA 127,518 143,646 147,325 117,790 536,280 115,466 117,321 156,240 141,852 530,879 136,297 by Business Sector RENEWABLES 156,817 223,269 229,742 151,261 761,090 150,793 193,881 234,556 173,859 753,089 166,691 EFFICIENT NAT. GAS 34,009 27,689 31,193 29,390 122,281 26,403 25,629 28,086 30,912 111,030 28,408 TRANSMISSION & TRANSP. 24,867 26,231 25,926 26,429 103,453 26,608 26,787 25,834 26,813 106,042 26,614 WATER 5,759 6,149 6,511 6,209 24,629 6,599 9,047 14,511 12,942 43,099 13,477 Total Revenue 221,452 283,338 293,373 213,289 1,011,452 210,403 255,344 302,987 244,526 1,013,260 235,190 1Q19 2Q19 3Q19 4Q19 2019 1Q20 2Q20 3Q20 4Q20 2020 1Q21 by Geography NORTH AMERICA 50,870 96,293 108,198 51,881 307,242 52,661 89,954 95,879 40,871 279,365 40,287 84.2% 92.5% 98.9% 88.8% 92.3% 88.8% 91.2% 87.4% 64.6% 84.4% 66.5% SOUTH AMERICA1 28,212 29,252 30,293 27,589 115,346 28,422 31,380 29,947 30,275 120,024 29,943 84.2% 82.2% 82.6% 75.6% 81.1% 79.7% 79.7% 81.0% 76.8% 79.2% 78.2% EMEA 102,024 103,807 109,177 83,959 398,968 84,879 92,773 115,132 103,950 396,734 99,840 80.0% 72.3% 74.1% 71.3% 74.4% 73.5% 79.1% 73.7% 73.3% 74.7% 73.3% by Business Sector RENEWABLES 123,484 177,910 192,168 110,517 604,079 113,670 161,415 181,788 119,412 576,285 115,857 78.7% 79.7% 83.6% 73.1% 79.4% 75.4% 83.3% 77.5% 68.7% 76.5% 69.5% EFFICIENT NAT. GAS 30,476 23,826 27,983 26,915 109,200 24,462 23,303 27,479 25,762 101,006 23,182 89.6% 86.1% 89.7% 91.6% 89.3% 92.6% 90.9% 97.8% 83.3% 91.0% 81.6% TRANSMISSION & TRANSP. 21,650 21,936 21,548 20,524 85,658 21,922 22,423 21,702 21,225 87,272 21,203 87.1% 83.6% 83.1% 77.6% 82.7% 82.4% 83.7% 84.0% 79.2% 82.3% 79.7% WATER 5,496 5,680 5,969 5,473 22,619 5,908 6,966 9,989 8,697 31,560 9,828 95.4% 92.4% 91.7% 88.1% 91.8% 89.5% 77.0% 68.8% 67.2% 73.2% 72.9% Total Adj. EBITDA incl. unconsolidated affiliates1 181,106 229,352 247,668 163,429 821,556 165,962 214,107 240,958 175,096 796,123 170,070 81.8% 80.9% 84.4% 76.6% 81.2% 78.9% 83.9% 79,5% 71.6% 78.6% 72.3% Revenue Adj. EBITDA incl. unconsolidated affiliates Adjusted EBITDA includes our share in EBITDA of unconsolidated affiliates. US $ in thousands

1Q19 2Q19 3Q19 4Q19 2019 1Q20 2Q20 3Q20 4Q20 2020 1Q21 RENEWABLES3 (GWh) 581 1,071 1,048 536 3,236 526 957 1,125 636 3,244 606 (GWh) 383 483 615 694 2,090 644 624 664 642 2,574 542 (availability %) 87.1% 89.9% 101.5% 101.4% 95.0% 102.4% 100.9% 103.8% 101.2% 102.1% 98.3% TRANSMISSION & TRANSP. (availab.%) 99.9% 100.0% 99.9% 100.0% 100.0% 99.9% 99.9% 100.0% 100.0% 100.0% 100.0% WATER (availability %) 99.8% 100.6% 103.6% 100.1% 101.2% 101.8% 102.2% 101.1% 95.4% 100.1% 97.5% 1Q19 2Q19 3Q19 4Q19 2019 1Q20 2Q20 3Q20 4Q20 2020 1Q21 RENEWABLES1 (MW) 1,496 1,496 1,496 1,496 1,496 1,496 1,551 1,551 1,551 1,551 1,591 EFF. NATURAL GAS2 (electric MW) 300 300 343 343 343 343 343 343 343 343 343 TRANSMISSION & TRANSP. (Miles) 1,152 1,152 1,152 1,166 1,166 1,166 1,166 1,166 1,166 1,166 1,166 WATER1 (Mft3/day) 10.5 10.5 10.5 10.5 10.5 10.5 17.5 17.5 17.5 17.5 17.5 Capacity in operation(at the end of the period) Production / Availability 5 5 5 Represents total installed capacity in assets owned or consolidated at the end of the period, regardless of our percentage of ownership in each of the assets.Includes 43 MW corresponding to our 30% share in Monterrey since August 2, 2019.Includes curtailment in wind assets for which we receive compensation.Major maintenance overhaul held in Q1 and Q2 2019 in ACT, as scheduled, which reduced production and electric availability as per the contract. GWh produced includes 30% of the production from Monterrey since August 2, 2019.Availability refers to the time during which the asset was available to our client totally or partially divided by contracted or budgeted availability, as applicable. EFFICIENT NATURAL GAS4 HISTORICAL FINANCIAL REVIEWKey Performance Indicators

1Q19 2Q19 3Q19 4Q19 2019 1Q20 2Q20 3Q20 4Q20 2020 1Q21 US 15.2% 39.8% 35.2% 16.3% 26.6% 18.2% 37.5% 35.2% 17.6% 27.1% 18.0% Spain 12.1% 26.7% 27.2% 6.7% 18.2% 8.0% 22.1% 28.6% 8.3% 16.8% 9.1% Kaxu 48.7% 27.8% 27.5% 45.4% 37.3% 28.9% 8.6% 26.8% 44.7% 27.3% 38.9% WIND2 Uruguay 33.0% 36.3% 40.9% 38.0% 37.2% 34.6% 40.8% 40.6% 42.8% 39.7% 32.6% SOLAR Historical Capacity Factors1 Capacity factor ratio represents actual electrical energy output over a given period of time to the maximum possible electrical energy output assuming continuous operation at full nameplate capacity over that period. Historical Capacity Factors are calculated from the date of entry into operation or the acquisition of each asset. Some capacity factors are not indicative of a full period of operations.Includes curtailment production in wind assets for which we receive compensation. HISTORICAL FINANCIAL REVIEWCapacity Factors

CURRENCY2 SECTOR GEOGRAPHY Based on CAFD estimates for the 2021-2025 period, including the acquisitions announced as of May 6, 2021. See “Disclaimer – Forward Looking Statements”.Including the effect of currency hedges. of long-term interest rates in projects are fixed or hedged2 ~ 90% 90 Denominatedin USD % > 73% Renewable13% Efficient Natural Gas11% Transmission & Transport. 3% Water 44% North America35% Europe13% South America 8% RoW SIZEABLE AND DIVERSIFIED ASSET PORTFOLIOPortfolio Breakdown Based on Estimated CAFD1

As of May 6, 2021 ASSET TYPE STAKE LOCATION GROSSCAPACITY OFFTAKER RATING1 YEARS INCONTRACT LEFT6 CURRENCY RENEWABLE ENERGY Solana 100% USA (Arizona) 280 MW APS A-/A2/A- 23 USD Mojave 100% USA (California) 280 MW PG&E BB-/WR/BB 19 USD Chile PV 1 35% Chile 55 MW n/a n/a n/a USD 4 Chile PV 2 35% Chile 40 MW n/a n/a n/a USD 4 Coso 100% USA (California) 135 MW SCPPA & two CCAs5 Investment grade5 19 USD Solaben 2/3 70% Spain 2x50 MW Kingdom of Spain A/Baa1/A- 17/17 EUR 3 Solacor 1/2 87% Spain 2x50 MW Kingdom of Spain A/Baa1/A- 16/16 EUR 3 PS 10/20 100% Spain 31 MW Kingdom of Spain A/Baa1/A- 11/13 EUR 3 Helioenergy 1/2 100% Spain 2x50 MW Kingdom of Spain A/Baa1/A- 16/16 EUR 3 Helios 1/2 100% Spain 2x50 MW Kingdom of Spain A/Baa1/A- 16/17 EUR 3 Solnova 1/3/4 100% Spain 3x50 MW Kingdom of Spain A/Baa1/A- 14/14/15 EUR 3 Solaben 1/6 100% Spain 2x50 MW Kingdom of Spain A/Baa1/A- 18/18 EUR 3 Seville PV 80% Spain 1 MW Kingdom of Spain A/Baa1/A- 15 EUR Kaxu 51% South Africa 100 MW Eskom BB/Ba2/BB-2 14 ZAR Palmatir 100% Uruguay 50 MW UTE BBB/Baa2/BBB-2 13 USD Cadonal 100% Uruguay 50 MW UTE BBB/Baa2/BBB-2 14 USD Melowind 100% Uruguay 50 MW UTE BBB/Baa2/BBB-2 15 USD Mini-Hydro 100% Peru 4 MW Peru BBB+/A3/BBB+ 12 USD EFFICIENT NATURAL GAS ACT 100% Mexico 300 MW Pemex BBB/Ba2/BB- 12 USD 4 Monterrey 30% Mexico 142 MW Industrial Customers Not rated 18 USD 4 TRANSMISSION & TRANSPORT. ATN 100% Peru 379 miles Peru BBB+/A3/BBB+ 20 USD 4 ATS 100% Peru 569 miles Peru BBB+/A3/BBB+ 23 USD 4 ATN 2 100% Peru 81 miles Minera Las Bambas Not rated 12 USD 4 Quadra 1/2 100% Chile 49 miles / 32 miles Sierra Gorda Not rated 14/14 USD 4 Palmucho 100% Chile 6 miles Enel Generacion Chile BBB+/Baa1 /A- 17 USD 4 Chile TL3 100% Chile 50 miles CNE A+/A1/A- Regulated USD 4 WATER Skikda 34% Algeria 3.5 Mft3/day Sonatrach & ADE Not rated 13 USD 4 Honaine 26% Algeria 7 Mft3/day Sonatrach & ADE Not rated 17 USD 4 Tenes 51% Algeria 7 Mft3/day Sonatrach & ADE Not rated 19 USD 4 Reflects the counterparties’ issuer credit ratings issued by S&P, Moody’s and Fitch, respectively, as of May 6, 2021.For Kaxu, it refers to the credit rating of the Republic of South Africa, and for Palmatir, Cadonal and Melowind, it refers to the credit rating of Uruguay, as UTE is unrated.Gross cash in euros dollarized through currency hedges.USD denominated but payable in local currency. AT A GLANCESizeable and Diversified Asset Portfolio (5) Southern California Public Power Authority, with AA- Rating from Fitch, and two Community Choice Aggregators: Silicon Valley Clean Energy and Monterrey Bar Community Power, both with A Rating from S&P.(6) Reflects the years in contract left as of December 31, 2021.

NON-GAAP FINANCIAL INFORMATIONReconciliation of Non-GAAP Measures Our management believes Adjusted EBITDA including unconsolidated affiliates and CAFD are useful to investors and other users of our financial statements in evaluating our operating performance because it provides them with an additional tool to compare business performance across companies and across periods. Adjusted EBITDA is widely used by investors to measure a company’s operating performance without regard to items such as interest expense, taxes, depreciation and amortization, which can vary substantially from company to company depending upon accounting methods and book value of assets, capital structure and the method by which assets were acquired. Our management believes CAFD is a relevant supplemental measure of the Company’s ability to earn and distribute cash returns to investors and is useful to investors in evaluating our operating performance because securities analysts and other interested parties use such calculations as a measure of our ability to make quarterly distributions. In addition, CAFD is used by our management team for determining future acquisitions and managing our growth. Adjusted EBITDA and CAFD are widely used by other companies in the same industry. Our management uses Adjusted EBITDA and CAFD as measures of operating performance to assist in comparing performance from period to period on a consistent basis. They also readily view operating trends as a measure for planning and forecasting overall expectations, for evaluating actual results against such expectations, and for communicating with our board of directors, shareholders, creditors, analysts and investors concerning our financial performance.We present non-GAAP financial measures because we believe that they and other similar measures are widely used by certain investors, securities analysts and other interested parties as supplemental measures of performance and liquidity. The non-GAAP financial measures may not be comparable to other similarly titled measures employed by other companies and they may have limitations as analytical tools. These measures may not be fit for isolated consideration or as a substitute for analysis of our operating results as reported under IFRS as issued by the IASB. Non-GAAP financial measures and ratios are not measurements of our performance or liquidity under IFRS as issued by the IASB. Thus, they should not be considered as alternatives to operating profit, profit for the period, any other performance measures derived in accordance with IFRS as issued by the IASB, any other generally accepted accounting principles or as alternatives to cash flow from operating, investing or financing activities. Some of the limitations of these non-GAAP measures are:they do not reflect our cash expenditures, future requirements for capital expenditures or contractual commitments; they do not reflect changes in, or cash requirements for, our working capital needs;they may not reflect the significant interest expense, or the cash requirements necessary, to service interest or principal payments, on our debts;although depreciation and amortization are non-cash charges, the assets being depreciated and amortized will often need to be replaced in the future and Adjusted EBITDA and CAFD do not reflect any cash requirements that would be required for such replacements;some of the exceptional items that we eliminate in calculating Adjusted EBITDA reflect cash payments that were made, or will be made in the future; andthe fact that other companies in our industry may calculate Adjusted EBITDA and CAFD differently than we do, which limits their usefulness as comparative measures.EBITDA has been used in this presentation exclusively for the announced acquisition of a wind portfolio in the United States. EBITDA has been calculated as profit/(loss) of the portfolio for the year 2020 after adding back depreciation, amortization, and impairment changes. There were no financing costs or income tax in 2020 in this portfolio.We define Adjusted EBITDA including unconsolidated affiliates as profit/(loss) for the period attributable to the Company, after adding back loss/(profit) attributable to non-controlling interest from continued operations, profit/(loss) from discontinued operations, income tax, share of profit/(loss) of associates carried under the equity method, finance expense net, depreciation, amortization and impairment charges. CAFD is calculated as cash distributions received by the Company from its subsidiaries minus cash expenses of the Company, including third party debt service and general and administrative expenses.

RECONCILIATIONReconciliation of Cash Available For Distribution and Adjusted EBITDA to Profit for the period attributable to the Company Adjusted EBITDA including unconsolidated affiliates includes our share in EBITDA of unconsolidated affiliates.“Deposits into/ withdrawals from restricted accounts” and “Change in non-restricted cash at project level” are calculated on a constant currency basis to reflect actual cash movements isolated from the impact of variations generated by foreign exchange changes during the period. (in thousands of U.S. dollars) For the three-month period ended March 31, 2021 2020 Profit/(loss) for the period attributable to the Company $ (19,172) $ (40,511) Profit/(loss) attributable to non-controlling interest 8,108 2,246 Profit/(loss) from discontinued operations (480) - Income tax 14,487 (10,147) Share of loss/(profit) of associates carried under the equity method (960) 668 Financial expense, net 81,247 100,534 Operating profit $ 83,230 $ 52,790 Depreciation, amortization, and impairment charges 83,541 109,619 Adjusted EBITDA $ 166,772 $ 162,409 Atlantica’s pro-rata share of EBITDA from unconsolidated affiliates 3,298 3,553 Adjusted EBITDA including unconsolidated affiliates1 $ 170,070 $ 165,962 Atlantica’s pro-rata share of EBITDA from unconsolidated affiliates (3,298) (3,553) Dividends from equity method investments 8,799 5,120 Non-monetary items (6,177) (4,334) Net interest and income tax paid (30,663) (11,436) Principal amortization of indebtedness (22,693) (14,898) Deposits into/ withdrawals from restricted accounts2 (26,576) 32,921 Change in non-restricted cash at project level2 (63,265) (50,467) Dividends paid to non-controlling interests (4,215) (4,915) Changes in other assets and liabilities 29,255 (66,843) Cash Available For Distribution $ 51,237 $ 47,558

RECONCILIATIONReconciliation of Adjusted EBITDA including unconsolidated affiliates to Net Cash Provided by Operating Activities (in thousands of U.S. dollars) For the three-month period ended March 31, 2021 2020 Net cash provided by operating activities $ 146,708 $ 85,685 Net interest and income tax paid 30,663 11,436 Changes in working capital (16,963) 59,333 Other non-cash adjustments and other 6,364 5,955 Adjusted EBITDA $ 166,772 $ 162,409 Atlantica’s pro-rata share of EBITDA from unconsolidated affiliates 3,298 3,553 Adjusted EBITDA including unconsolidated affiliates1 $ 170,070 $ 165,962 Adjusted EBITDA including unconsolidated affiliates includes our share in EBITDA of unconsolidated affiliates.

RECONCILIATIONReconciliation of Adjusted EBITDA Margin including unconsolidated affiliates to Operating Profit Margin and Other Reconciliations Adjusted EBITDA including unconsolidated affiliates includes our share in EBITDA of unconsolidated affiliates. (in thousands of U.S. dollars) For the three-month period ended March 31, 2021 2020 Revenue $ 235,190 $ 210,403 Profit/(loss) for the period attributable to the Company $ (19,172) $ (40,511) Profit/(loss) attributable to non-controlling interest 8,108 2,246 Profit/(loss) from discontinued operations (480) - Income tax 14,487 (10,147) Share of loss/(profit) of associates carried under the equity method (960) 668 Financial expense, net 81,247 100,534 Operating profit $ 83,230 $ 52,790 Operating profit margin % 35.4 % 25.1 Depreciation, amortization, and impairment charges 35.5 52.1 Adjusted EBITDA margin % 70.9 % 77.2 Atlantica’s pro-rata share of EBITDA from unconsolidated affiliates 1.4 1.6 Adjusted EBITDA Margin including unconsolidated affiliates1 % 72.3 % 78.8 (in millions of U.S. dollars) Full Year 20201 Net Income $ 33.0 Depreciation and amortization 35.2 EBITDA $ 68.2 Reconciliation of Wind Portfolio Acquisition EBITDA to Net Income Reconciliation of Adjusted EBITDA Margin including unconsolidated affiliates to Operating Profit Margin