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, 2023
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 20 7098 4384

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

Q1 2023 Earnings Presentation May 5, 2023

DISCLAIMER Forward Looking Statements This 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. In some cases, you can identify forward-looking statements by terminology such as "anticipate," "believe," "could," "estimate," "expect,“, "guidance," "may," "plan,“ "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 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 4.B. Information on the Company—Business Overview", each in our Annual Report on Form 20-F for the fiscal year ended December 31, 2022, filed with the Securities and Exchange Commission (“SEC”), 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: our anticipated exposure to current market risks, including the potential impact from foreign exchange rates and interest rates on cash available for distribution (“CAFD”); equity investments; CAFD estimates, including per currency, geography and sector; net corporate leverage based on CAFD estimates; debt refinancing; the performance of our long-term contracts; self-amortizing project debt structure and debt reduction; the use of non-GAAP measures as a useful tool for investors; the possibility to extend asset life; 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 on Form 20-F for the fiscal year ended December 31, 2022 filed with the SEC. The CAFD guidance used in this presentation was estimated as of March 1, 2023. This estimate is based on assumptions believed to be reasonable as of the date Atlantica Sustainable Infrastructure plc (“Atlantica”, the “Company”, “we” or “us”) published its 2022 Financial Results. We disclaim any current intention to update such guidance, except as required by law. Non-GAAP Financial Measures This presentation also includes certain non-GAAP financial measures, including Adjusted EBITDA, CAFD and CAFD per share. 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 net cash provided by operating activities 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, CAFD per share 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 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 that 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 be a substitute for recorded amounts presented in conformity with IFRS as issued by the IASB nor should such amounts be considered in isolation.

Key Messages Revenue and Adjusted EBITDA year-over-year growth of 1.5%1 and 4.0%1 in Q1 2023 on a comparable basis Compared to Q1 2022, on a constant currency basis Compared to Q1 2022, excluding $4.1 million from the sale of part of our equity interest in our development company in Colombia to a partner in Q1 2023. Q1 2023 dividend of $0.445 per share +12.1% year-over-year CAFD growth in Q1 2023 up to $61.0 million and +4.6%2 year-over-year growth on a comparable basis

∆ Excluding FX impact US$ in million (except CAFD per share) 2023 2022 ∆ Reported Revenue 242.5 247.5 (2.0)% Adjusted EBITDA 174.2 173.6 0.3% CAFD 61.0 54.4 12.1% CAFD per share2 0.53 0.48 8.9% HIGHLIGHTS 12.1% CAFD Growth in Q1 2023 Compared to Q1 2022, on a constant currency basis. CAFD per share is calculated by dividing CAFD for the period by the weighted average number of shares for the period (see reconciliation on page 23). Compared to Q1 2022, excluding $4.1 million from the sale of part of our equity interest in our development company in Colombia to a partner in Q1 2023. 1.5%1 4.0%1 First Quarter 4.6%3 1.5%3

HIGHLIGHTS Performance by Region and Sector WATER Q1 2023 Q1 2022 ∆ 13.7 13.5 +1% 9.0 9.2 (2)% RENEWABLES US$ in million Q1 2023 Q1 2022 ∆ ∆ Excl. FX impact1 Revenue 172.6 182.1 (5)% 0% Adjusted EBITDA 119.1 122.2 (3)% +3% EFFICIENT NAT. GAS & HEAT Q1 2023 Q1 2022 ∆ 27.4 25.3 +8% 22.6 21.7 +4% TRANSMISSION LINES Q1 2023 Q1 2022 ∆ 28.8 26.6 +8% 23.5 20.5 15% By Sector EMEA NORTH AMERICA US$ in million Q1 2023 Q1 2022 ∆ Revenue 72.8 74.4 (2)% Adjusted EBITDA 52.0 58.3 (11%) SOUTH AMERICA Q1 2023 Q1 2022 ∆ ∆ Excl. FX impact1 126.0 134.6 (6)% 0% 88.4 86.2 +3% +10% By Region Q1 2023 Q1 2022 ∆ 43.7 38.5 +14% 33.8 29.1 +16% Compared to Q1 2022, on a constant currency basis.

Includes 49% of Vento II production since its acquisition. Includes curtailment in wind assets for which we receive compensation. 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, except for Vento II, for which we have included our 49% interest. GWh produced includes 30% share 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 and 55 MWt corresponding to thermal capacity from Calgary District Heating. WATER RENEWABLES TRANSMISSION LINES EFFICIENT NATURAL GAS & HEAT Q1 2023 Q1 2022 Availability4 100.8% 104.5% M ft3 in operation2 17.5 17.5 Q1 2023 Q1 2022 GWh produced1 1,192 1,094 MW in operation2 2,161 2,044 Q1 2023 Q1 2022 GWh produced3 600 625 Availability4 94.9% 100.3% MW in operation5 398 398 Q1 2023 Q1 2022 Availability4 100.0% 99.9% Miles in operation 1,229 1,229 KEY OPERATIONAL METRICS Steady Operational Performance

Net debt corresponds to gross debt including accrued interest less cash and cash equivalents. Net corporate debt is calculated as long-term corporate debt plus short-term corporate debt minus cash and cash equivalents at Atlantica’s corporate level. Net project debt is calculated as long-term project debt plus short-term project debt minus cash and cash equivalents at the consolidated project level. Net corporate leverage is calculated as net corporate debt divided by midpoint 2023 CAFD guidance before corporate debt service. CAFD before corporate debt service is calculated as CAFD plus corporate debt interest paid by Atlantica. US$ in million As of Mar. 31, 2023 As of Dec. 31, 2022 Net Corporate Debt2 968.0 956.4 Net Project Debt3 4,103.1 4,012.9 Net Corporate debt / CAFD pre corporate debt service4 3.3x NET DEBT Net Corporate Debt to CAFD pre corporate interest at 3.3x Net Debt Position1

Appendix

CURRENCY SECTOR GEOGRAPHY Based on CAFD estimates for the 2023-2026 period as of March 1, 2023, for the assets as of December 31, 2022, including assets that have reached COD before March 1, 2023. See “Disclaimer – Forward Looking Statements”. Euro denominated cash flows from Spanish assets, net of euro-denominated corporate interest payments and general and administrative expenses, are hedged through currency options on a rolling basis 100% for the next 12 months and 75% for the following 12 months. Based on weighted outstanding debt as of March 31, 2023. of interest rates in project debt are fixed or hedged3 90 Denominated in USD or hedged1,2 % > 70% Renewable 15% Eff. Natural Gas & Heat 12% Transmission Lines 3% Water 40% North America 34% Europe 18% South America 8% RoW SIZEABLE AND DIVERSIFIED ASSET PORTFOLIO Portfolio Breakdown Based on Estimated CAFD1 INTEREST RATES ~92 %

Consolidated cash as of March 31, 2023, increase by $1.9 million vs December 31, 2022, including FX translation differences of $1.4 million. CASH FLOW Operating Cash Flow US$ in million 2023 2022 Adjusted EBITDA 174.2 XX 173.6 Share in Adjusted EBITDA of unconsolidated affiliates (11.8) (14.2) Net interest and income tax paid (30.2) (16.5) Changes in working capital (93.3) ) (19.0) Non-monetary adjustments and other 2.8 13.4 OPERATING CASH FLOW 41.7 137.3 Acquisitions of subsidiaries and entities under the equity method and investments in assets under development and construction (9.5) (42.6) Distributions from entities under the equity method & other 10.4 29.7 INVESTING CASH FLOW 0.9 (12.9) FINANCING CASH FLOW (42.1) (8.8) Net change in consolidated cash1 0.4 115.6 First Quarter

HISTORICAL FINANCIAL REVIEW Key Financials by Quarter (1/2) “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 to this presentation. Dividends are paid to shareholders in the quarter after they are declared. (3) Number of shares outstanding on the record date corresponding to each dividend, except the shares issued under the ATM program between the dividend declaration date and the dividend record date, as applicable. 1Q21 2Q21 3Q21 4Q21 2021 1Q22 2Q22 3Q22 4Q22 2022 1Q23 Revenue 268,178 342,997 329,244 271,331 1,211,749 247,452 307,832 303,121 243,624 1,102,029 242,509 Adjusted EBITDA 171,249 232,985 229,846 190,307 824,388 173,626 228,678 228,336 166,459 797,100 174,204 Atlantica’s pro-rata share of EBITDA from unconsolidated affiliates (3,298) (4,295) (8,451) (15,013) (31,057) (14,202) (15,988) (7,387) (8,192) (45,769) (11,796) Non-monetary items (6,834) 8,625 33,675 20,346 55,809 10,413 10,940 10,839 (4,196) 27,996 649 Accounting provision for electricity market prices in Spain (659) 11,643 41,582 24,489 77,055 7,141 10,585 10,507 (2,980) 25,253 (1,153) Difference between billings and revenue in assets accounted for as concessional financial assets 8,501 11,659 6,771 11,959 38,890 18,169 15,050 14,978 13,434 61,630 16,441 Income from cash grants in the US (14,678) (14,678) (14,678) (14,678) (58,711) (14,897) (14,695) (14,645) (14,650) (58,888) (14,639) Other non-monetary items - - - (1,424) (1,424) - - - - - - Maintenance Capex (3,278) (1,098) (246) (13,100) (17,722) (2,844) (3,614) (7,283) (4,847) (18,588) (7,630) Dividends from unconsolidated affiliates 8,799 4,431 11,385 10,268 34,883 31,870 11,921 12,411 11,493 67,695 12,401 Net interest and income tax paid (30,872) (132,857) (45,301) (133,234) (342,263) (16,546) (112,705) (32,885) (115,148) (277,284) (30,179) Changes in other assets and liabilities 35,459 (1,699) (11,873) 21,806 43,696 (5,588) 6,415 52,186 49,885 102,896 (92,980) Deposits into/withdrawals from debt service accounts1 (29,639) 17,229 (8,456) 23,595 2,729 11,805 8,020 (20,503) 33,696 33,018 9,820 Change in non-restricted cash at project companies1 (71,162) 47,730 (89,947) 115,588 2,209 (103,116) 51,501 (135,718) 125,662 (61,672) 43,114 Dividends paid to non-controlling interests (4,215) (7,395) (11,717) (4,807) (28,134) (6,221) (9,800) (10,421) (12,767) (39,209) (6,011) Principal amortization of indebtedness net of new indebtedness at projects (14,972) (104,999) (40,336) (158,684) (318,991) (24,789) (112,427) (27,912) (183,183) (348,311) (30,543) Cash Available For Distribution (CAFD) 51,237 58,657 58,580 57,073 225,547 54,407 62,941 61,662 58,862 237,872 61,049 Dividends declared2 47,643 47,807 48,493 49,479 193,422 50,202 51,332 51,645 51,645 204,824 51,688 # of shares3 110,797,738 111,178,846 111,477,263 112,451,438 114,095,845 115,352,085 116,055,126 116,055,126 116,153,273 DPS (in $ per share) 0.43 0.43 0.435 0.44 1.735 0.44 0.445 0.445 0.445 1.775 0.445 Key Financials US$ in thousands

Debt Details 1Q21 2Q21 3Q21 4Q21 2021 1Q22 2Q22 3Q22 4Q22 2022 1Q23 Project Debt 5,200.2 5,374.2 5,278.9 5,036.2 5,036.2 5,037.0 4,735.5 4,621.9 4,553.1 4,553.1 4,596.6 Project Cash (624.6) (603.1) (685.0) (534.4) (534.4) (625.9) (545.1) (675.8) (540.2) (540.2) (493.5) Net Project Debt 4,575.6 4,771.1 4,593,9 4,501.8 4,501.8 4,411.1 4,190.4 3,946.1 4,012.9 4,012.9 4,103.1 Corporate Debt 965.3 1,025.1 1,030.1 1,023.1 1,023.1 1,056.1 1,000.1 955.5 1,017.2 1,017.2 1,077.4 Corporate Cash (434.2) (83.2) (78.6) (88.3) (88.3) (113.1) (123.1) (105.8) (60.8) (60.8) (109.4) Net Corporate Debt 531.1 941.8 951.5 934.8 934.8 943.0 877.0 849.7 956.4 956.4 968.0 Total Net Debt 5,106.7 5,713.0 5,545.1 5,436.6 5,436.6 5,354.1 5,067.4 4,795.8 4,969.3 4,969.3 5,071.1 Net Corporate Debt / CAFD pre corporate interests1 2.6x2 3.4x 3.5x 3.5x 3.5x 3.3x 3.1x 3.0x 3.4x 3.4x 3.3x HISTORICAL FINANCIAL REVIEW Key Financials by Quarter (2/2) US$ in million (1) Ratios presented are the ratios shown on each earnings presentation relating to such period. (2) Net corporate debt as of March 31, 2021, was calculated pro-forma including the payment of $170 million for the Coso investment ($130 million equity investment paid in April 2021 and additional $40 million paid in July 2021 to reduce debt).

HISTORICAL FINANCIAL REVIEW Segment Financials by Quarter 1Q21 2Q21 3Q21 4Q21 2021 1Q22 2Q22 3Q22 4Q22 2022 1Q23 by Geography NORTH AMERICA 60,585 118,216 129,860 87,114 395,775 74,304 124,968 124,423 81,352 405,047 72,840 SOUTH AMERICA 38,308 40,043 38,778 37,856 154,985 38,528 39,804 44,217 43,892 166,441 43,720 EMEA 169,285 217,726 160,606 146,361 660,989 134,620 143,060 134,481 118,380 530,541 125,949 by Business Sector RENEWABLES 199,679 271,945 254,132 202,768 928,525 182,101 238,234 232,423 168,619 821,377 172,600 EFFICIENT NAT. GAS & HEAT 28,408 30,097 35,019 30,168 123,692 25,327 28,091 28,526 31,647 113,591 27,403 TRANSMISSION LINES 26,614 26,975 26,840 25,251 105,680 26,620 28,234 28,425 29,994 113,273 28,831 WATER 13,477 13,979 13,253 13,143 53,852 13,404 13,273 13,747 13,364 53,788 13,674 Total Revenue 268,178 342,996 329,244 271,331 1,211,749 247,452 307,832 303,121 243,624 1,102,029 242,509 1Q21 2Q21 3Q21 4Q21 2021 1Q22 2Q22 3Q22 4Q22 2022 1Q23 by Geography NORTH AMERICA 40,287 94,574 108,500 68,442 311,803 58,266 102,913 96,981 51,828 309,988 51,969 SOUTH AMERICA 29,943 30,279 30,404 28,921 119,547 29,129 29,715 36,236 31,471 126,551 33,788 EMEA 101,019 108,133 90,942 92,944 393,038 86,231 96,051 95,118 83,161 360,561 88,447 by Business Sector RENEWABLES 117,036 177,995 169,830 137,722 602,583 122,223 174,606 173,022 118,165 588,016 119,122 EFFICIENT NAT. GAS & HEAT 23,182 24,039 29,166 23,548 99,935 21,699 22,315 22,794 17,752 84,560 22,610 TRANSMISSION LINES 21,203 21,319 21,721 19,392 83,635 20,523 22,656 23,047 21,784 88,010 23,470 WATER 9,828 9,633 9,129 9,645 38,235 9,181 9,102 9,473 8,758 36,514 9,002 Total Adjusted EBITDA 171,249 232,985 229,846 190,307 824,388 173,626 228,678 228,336 166,459 797,100 174,204 Adjusted EBITDA Revenue US $ in thousands

1Q21 2Q21 3Q21 4Q21 2021 1Q22 2Q22 3Q22 4Q22 2022 1Q23 RENEWABLES3 (GWh) 606 1,377 1,477 1,195 4,655 1,094 1,554 1,507 1,164 5,319 1,192 (GWh)4 542 501 622 627 2,292 625 626 647 603 2,501 600 (availability %)5 98.3% 100.1% 101.1% 103.0% 100.6% 100.3% 99.9% 101.1% 95.1% 98.9% 94.9% TRANSMISSION LINES (availability %)5 100.0% 99.9% 100.0% 100.0% 100.0% 99.9% 99.9% 100.0% 100.0% 100.0% 100.0% WATER (availability %)5 97.5% 101.9% 99.8% 91.9% 97.9% 104.5% 99.9% 103.3% 101.4% 102.3% 100.8% 1Q21 2Q21 3Q21 4Q21 2021 1Q22 2Q22 3Q22 4Q22 2022 1Q23 RENEWABLES1 (MW) 1,591 2,018 2,022 2,044 2,044 2,044 2,048 2,121 2,121 2,121 2,161 EFFICIENT NAT. GAS & HEAT2 (MW) 343 398 398 398 398 398 398 398 398 398 398 TRANSMISSION LINES (Miles) 1,166 1,166 1,166 1,166 1,166 1,229 1,229 1,229 1,229 1,229 1,229 WATER1 (Mft3/day) 17.5 17.5 17.5 17.5 17.5 17.5 17.5 17.5 17.5 17.5 17.5 Capacity in operation (at the end of the period) Production / Availability 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, except for Vento II, for which we have included our 49% interest. Includes 43 MW corresponding to our 30% share in Monterrey and 55 MWt corresponding to thermal capacity from Calgary District Heating since May 14, 2021. Includes 49% of Vento II production since its acquisition. Includes curtailment in wind assets for which we receive compensation. GWh produced includes 30% share 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. EFFICIENT NAT. GAS & HEAT HISTORICAL FINANCIAL REVIEW Key Performance Indicators

Historical Capacity Factors1 1Q21 2Q21 3Q21 4Q21 2021 1Q22 2Q22 3Q22 4Q22 2022 1Q23 SOLAR US 18.0% 38.6% 31.0% 17.0% 26.1% 17.2% 39.1% 32.4% 16.6% 26.3% 15.2% Chile2 28.4% 20.9% 20.6% 25.8% 23.9% 25.3% 20.4% 24.6% 28.8% 24.8% 27.6% Spain 9.1% 24.8% 29.6% 10.7% 18.6% 7.3% 23.6% 27.9% 5.8% 16.2% 11.7% Italy - - 18.6% 8.3% 16.5% 12.7% 19.7% 20.0% 9.2% 15.4% 11.8% Kaxu 38.9% 26.9% 20.2% 48.4% 33.6% 36.9% 27.2% 28.8% 44.6% 34.4% 45.2% US - - 21.6% 35.4% 28.3% 38.1% 35.6% 20.3% 34.8% 32.2% 37.7% Uruguay3 32.6% 38.3% 38.2% 38.3% 36.9% 34.5% 27.7% 38.2% 41.8% 35.6% 33.6% Capacity factor ratio represents actual electrical energy output over a given period of time divided by 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 Chile PV 2 since Q1 2021 and Chile PV 3 since Q3 2022. Includes curtailment production in wind assets for which we receive compensation. WIND HISTORICAL FINANCIAL REVIEW Capacity Factors

Exchange rates as of March 31, 2023 (EUR/USD = 1.0730) and December 31, 2022 (EUR/USD = 1.0705). Restricted cash is cash which is restricted generally due to requirements of certain project finance agreements. US $ in million1 As of Mar. 31 2023 As of Dec. 31 2022 Corporate cash at Atlantica 109.4 60.8 Existing available revolver capacity 365.1 385.1 Total Corporate Liquidity 474.5 445.9 Cash at project companies 493.5 540.2 - Restricted2 202.0 207.6 - Other 291.5 332.6 LIQUIDITY Liquidity Position

Key principle: non-recourse project financing in ring-fenced subsidiaries 100% project debt self-amortizing progressively before the end of the contracted life Low interest rate risk, with +92% of interest rates fixed or hedged ~$2bn planned debt reduction in the next 5 years1 FINANCING Self-Amortizing Project Debt Structure Project debt amortization schedule as of December 31, 2022. Does not include new project debt.

Weighted Average Life Project debt term PPAs with predefined prices for ~14 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 Calculated as weighted average years remaining as of March 31, 2023 based on CAFD estimates for the 2023-2026 period, including assets that have reached COD before March 1, 2023. See “Disclaimer – Forward Looking Statements”. Regulation term in the case of Spain and Chile TL3. (3) From the total amount of $211 million project debt, $74 million are progressively repaid following a theoretical 2036 maturity, with a legal maturity in 2027. The remaining $137 million are expected to be refinanced in or before 2027. LONG-TERM STABLE CASH FLOW Portfolio of Assets 3

CORPORATE DEBT DETAILS Corporate Debt as of March 31, 2023 No significant maturities in the near term Exchange rates as of March 31, 2023 (EUR/USD = 1.0905). Amounts include principal amounts outstanding, unless stated otherwise. As of March 31, 2023, letters of credit with face value in an amount equal to $24.9 million were outstanding and $365.1 million was available under the Revolving Credit Facility. The latter has a total limit of $450 million. US $ in million1 Maturity Amounts2 Credit Facilities (Revolving Credit Facility)3 2024 59.5 (Other facilities)4 2023 – 2028 50.4 Green Exchangeable Notes5 2025 107.8 2020 Green Private Placement6 (€ denominated) 2026 314.3 Note Issuance Facility 20207 (€ denominated) 2027 150.1 Green Senior Notes8 2028 395.3 Total 1,077.4 Other facilities include the Commercial Paper Program, accrued interest payable and other debt. 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. Senior unsecured note facility dated July 8, 2020, of €140 million. Green Senior Unsecured Notes dated May 18, 2021, of $400 million.

Our management believes Adjusted EBITDA, CAFD and CAFD per share are useful to investors and other users of our financial statements in evaluating our operating performance because such measures provide investors with additional tools 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 and CAFD per share are 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 and CAFD per share are used by our management team for determining future acquisitions and managing our growth. Our management uses Adjusted EBITDA, CAFD and CAFD per share as measures of operating performance to assist in comparing performance from period to period and aims to use them on a consistent basis moving forward. 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. Adjusted EBITDA, CAFD and CAFD per share are widely used by other companies in the same industry. 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, CAFD and CAFD per share 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; and the fact that other companies in our industry may calculate Adjusted EBITDA, CAFD and CAFD per share differently than we do, which limits their usefulness as comparative measures. We define Adjusted EBITDA as profit/(loss) for the period attributable to the parent company, after previously adding back loss/(profit) attributable to non-controlling interest, income tax expense, financial expense (net), depreciation, amortization and impairment charges of entities included in our consolidated financial statements and depreciation and amortization, financial expense and income tax expense of unconsolidated affiliates (pro-rata of our equity ownership). CAFD is calculated as cash distributions received by the Company from its subsidiaries minus cash expenses of the Company, including debt service and general and administrative expenses. CAFD per share is calculated by dividing CAFD for the period by weighted average number of shares for the period. NON-GAAP FINANCIAL INFORMATION Reconciliation of Non-GAAP Measures

Information presented as the pro-rata share of our unconsolidated affiliates reflects our proportionate ownership of each asset in our property portfolio that we do not consolidate and has been calculated by multiplying our unconsolidated affiliates’ financial statement line items by our percentage ownership thereto. Note 7 to our consolidated financial statements as of and for the period ended March 31, 2023 includes a description of our unconsolidated affiliates and our pro rata share thereof. We do not control the unconsolidated affiliates. Multiplying our unconsolidated affiliates’ financial statement line items by our percentage ownership may not accurately represent the legal and economic implications of holding a noncontrolling interest in an unconsolidated affiliate. We include pro-rata share of depreciation and amortization, financial expense and income tax expense of unconsolidated affiliates because we believe it assists investors in estimating the effect of such items in the profit/(loss) of entities carried under the equity method (which is included in the calculation of our Adjusted EBITDA) based on our economic interest in such unconsolidated affiliates. Each unconsolidated affiliate may report a specific line item in its financial statements in a different manner. In addition, other companies in our industry may calculate their proportionate interest in unconsolidated affiliates differently than we do, limiting the usefulness of such information as a comparative measure. Because of these limitations, the information presented as the pro-rata share of our unconsolidated affiliates should not be considered in isolation or as a substitute for our or such unconsolidated affiliates’ financial statements as reported under applicable accounting principles. NON-GAAP FINANCIAL INFORMATION Reconciliation of Non-GAAP Measures

“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 2023 2022 Profit/(loss) for the period attributable to the Company (10,990) (12,042) Profit/(loss) attributable to non-controlling interest 5,017 2,200 Income tax (9,656) (3,906) Depreciation and amortization, financial expense and income tax expense of unconsolidated affiliates (pro rata of our equity ownership) 5,609 5,982 Financial expense, net 80,434 80,467 Depreciation, amortization, and impairment charges 103,790 100,925 Adjusted EBITDA 174,204 173,626 Atlantica’s pro-rata share of EBITDA from unconsolidated affiliates (11,796) (14,202) Non-monetary items 649 10,413 Accounting provision for electricity market prices in Spain (1,153) 7,141 Difference between billings and revenue in assets accounted for as concessional financial assets 16,441 18,169 Income from cash grants in the US (14,639) (14,897) Maintenance Capex (7,630) (2,844) Dividends from equity method investments 12,401 31,870 Net interest and income tax paid (30,179) (16,546) Changes in other assets and liabilities (92,980) (5,588) Deposits into/ withdrawals from restricted accounts1 9,820 11,805 Change in non-restricted cash at project level1 43,114 (103,116) Dividends paid to non-controlling interests (6,011) (6,221) Debt principal repayments (30,543) (24,789) Cash Available For Distribution 61,049 54,407 RECONCILIATION Reconciliation of CAFD and Adjusted EBITDA to Profit for the period attributable to the Company

RECONCILIATION Reconciliation of Adjusted EBITDA to Net Cash Provided by Operating Activities (in thousands of U.S. dollars) For the three-month period ended March 31 For the three-month period ended June 30 2023 2022 Net cash provided by operating activities 41,706 137,315 Net interest and income tax paid 30,179 16,546 Changes in working capital 93,263 19,047 Non-monetary items & other (2,740) (13,484) Atlantica’s pro-rata share of EBITDA from unconsolidated affiliates 11,796 14,202 Adjusted EBITDA 174,204 173,626 Reconciliation of CAFD to CAFD per share For the three-month period ended March 31 2023 2022 CAFD (in thousands of U.S. dollars) 61,049 54,407 Weighted average number of shares (basic) for the period (in thousands) 116,140 112,741 CAFD per share (in U.S. dollars) 0.5257 0.4826

As of May 5, 2023 ASSET TYPE STAKE LOCATION GROSSCAPACITY OFFTAKER RATING1 YEARS INCONTRACT LEFT6 CURRENCY RENEWABLE ENERGY Solana 100% USA (Arizona) 280 MW APS BBB+/A3/BBB+ 21 USD Mojave 100% USA (California) 280 MW PG&E BB-/Ba2/BB+ 17 USD Coso 100% USA (California) 135 MW SCPPA & two CCAs4 Investment grade4 19 USD Elkhorn Valley7 49% USA (Oregon) 101 MW Idaho Power Company BBB/Baa1/-- 5 USD Prairie Star7 49% USA (Minnesota) 101 MW Great River Energy --/A3/A- 5 USD Twin Groves II7 49% USA (Illinois) 198 MW Exelon Generation Co. BBB/Baa2/-- 3 USD Lone Star II7 49% USA (Texas) 196 MW n/a n/a n/a USD Chile PV 1 35% Chile 55 MW n/a n/a n/a USD3 Chile PV 2 35% Chile 40 MW n/a Not rated 8 USD3 Chile PV 3 35% Chile 73 MW n/a n/a n/a USD3 La Sierpe 100% Colombia 20 MW Coenersa5 Not rated 13 COP La Tolua 100% Colombia 20 MW Coenersa5 Not rated 10 COP Tierra Linda 100% Colombia 10 MW Coenersa5 Not rated 10 COP Albisu 100% Uruguay 10 MW Montevideo Refrescos Not rated 15 UYU Palmatir 100% Uruguay 50 MW UTE BBB+/Baa2/BBB-2 11 USD Cadonal 100% Uruguay 50 MW UTE BBB+/Baa2/BBB-2 12 USD Melowind 100% Uruguay 50 MW UTE BBB+/Baa2/BBB-2 13 USD Mini-Hydro 100% Peru 4 MW Peru BBB/Baa1/BBB 10 USD3 Reflects the counterparties’ issuer credit ratings issued by S&P, Moody’s and Fitch, respectively, as of May 3, 2023. It refers to the credit rating of Uruguay, as UTE is unrated. USD denominated but payable in local currency. Refers to the credit rating of two Community Choice Aggregators: Silicon Valley Clean Energy and Monterrey Bar Community Power, both with A rating from S&P; Southern California Public Power Authority, the third off-taker, is not rated. AT A GLANCE Sizeable and Diversified Asset Portfolio (5) Largest electricity wholesaler in Colombia. (6) As of March 31, 2023. (7) Part of Vento II portfolio.

As of May 5, 2023 ASSET TYPE STAKE LOCATION GROSSCAPACITY OFFTAKER RATING1 YEARS INCONTRACT LEFT6 CURRENCY RENEWABLE ENERGY Solaben 2/3 70% Spain 2x50 MW Kingdom of Spain A/Baa1/A- 14/15 EUR4 Solacor 1/2 87% Spain 2x50 MW Kingdom of Spain A/Baa1/A- 14/14 EUR4 PS 10/20 100% Spain 31 MW Kingdom of Spain A/Baa1/A- 9/11 EUR4 Helioenergy 1/2 100% Spain 2x50 MW Kingdom of Spain A/Baa1/A- 14/14 EUR4 Helios 1/2 100% Spain 2x50 MW Kingdom of Spain A/Baa1/A- 14/14 EUR4 Solnova 1/3/4 100% Spain 3x50 MW Kingdom of Spain A/Baa1/A- 12/12/12 EUR4 Solaben 1/6 100% Spain 2x50 MW Kingdom of Spain A/Baa1/A- 15/15 EUR4 Seville PV 80% Spain 1 MW Kingdom of Spain A/Baa1/A- 13 EUR4 Italy PV 1 100% Italy 1.6 MW Italy BBB/Baa3/BBB 8 EUR4 Italy PV 2 100% Italy 2.1 MW Italy BBB/Baa3/BBB 8 EUR4 Italy PV 3 100% Italy 2.5 MW Italy BBB/Baa3/BBB 9 EUR4 Italy PV 4 100% Italy 3.6 MW Italy BBB/Baa3/BBB 8 EUR4 Kaxu 51% South Africa 100 MW Eskom BB-/Ba2/BB-2 12 ZAR EFFICIENT NAT. GAS & HEAT Calgary 100% Canada 55 MWt 22 High quality clients3 ~41% A+ or higher3 18 CAD ACT 100% Mexico 300 MW Pemex BBB/B1/BB- 10 USD5 Monterrey 30% Mexico 142 MW Industrial Customers Not rated 23 USD5 TRANSMISSION LINES ATN 100% Peru 379 miles Peru BBB/Baa1/BBB 18 USD5 ATS 100% Peru 569 miles Peru BBB/Baa1/BBB 21 USD5 ATN 2 100% Peru 81 miles Minera Las Bambas Not rated 10 USD5 Quadra 1/2 100% Chile 49 miles / 32 miles Sierra Gorda Not rated 12/12 USD5 Palmucho 100% Chile 6 miles Enel Generacion Chile BBB/-/BBB+ 15 USD5 Chile TL 3 100% Chile 50 miles CNE A/A2/A- n/a USD5 Chile TL 4 100% Chile 63 miles Several Mini-hydro plants Not rated 49 USD WATER Skikda 34% Algeria 3.5 Mft3/day Sonatrach & ADE Not rated 11 USD5 Honaine 26% Algeria 7 Mft3/day Sonatrach & ADE Not rated 14 USD5 Tenes 51% Algeria 7 Mft3/day Sonatrach & ADE Not rated 17 USD5 Reflects the counterparties’ issuer credit ratings issued by S&P, Moody’s and Fitch, respectively, as of May 3, 2023. It refers to the credit rating of the Republic of South Africa. Diversified mix of 22 high credit quality clients (~41% A+ rating or higher, the rest unrated). AT A GLANCE Sizeable and Diversified Asset Portfolio (4) Gross cash in euros dollarized through currency hedges. (5) USD denominated but payable in local currency. (6) As of March 31, 2023.

Great West House, GW1, 17th floor, Great West Road Brentford TW8 9DF London (United Kingdom)

SIGNATURES
Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

| ATLANTICA SUSTAINABLE INFRASTRUCTURE PLC
| /s/ Santiago Seage
| Name: | Santiago Seage
| Title: | Chief Executive Officer
Date: May 5, 2023 |