We have acted as counsel to AvalonBay Communities, Inc., a Maryland corporation (the “Company”), in connection with the merger (the “Merger”) of the Company with and into Canopy Merger Sub LLC, a Maryland limited liability company (“Merger Sub”) and a wholly-owned subsidiary of Equity Residential, a Maryland real estate investment trust (“Parent”), pursuant to the Agreement and Plan of Merger, dated as of May 20, 2026 (the “Merger Agreement”), by and among Parent, Merger Sub, ERP Operating Limited Partnership, an Illinois limited partnership (“Parent OP”), and the Company.

We are providing this opinion letter to be filed as an exhibit to the registration statement on Form S-4 (File No. 333-297128), including the joint proxy statement/prospectus contained therein at the time the Registration Statement (as defined below) is declared effective, initially filed with the Securities and Exchange Commission (the “Commission”) under the Securities Act of 1933, as amended (the “Securities Act”), on June 29, 2026, as amended by Amendment No. 1 thereto filed with the Commission on the date hereof (as amended, excluding the documents incorporated by reference therein, the “Registration Statement”) with respect to the transactions contemplated by the Merger Agreement.  This opinion relates to the Company’s qualification for U.S. federal income tax purposes as a real estate investment trust (a “REIT”) under the Internal Revenue Code of 1986, as amended (the “Code”), for the taxable years commencing with the Company’s taxable year ended December 31, 1994 through the Company’s taxable year ending with the Merger.  Capitalized terms not otherwise defined herein shall have the meaning ascribed to them in the Merger Agreement.

Equity Residential

As of July 9, 2026

Page 2

We also assume that (i) each of the Asset Contribution and the Merger will be consummated in accordance with the Merger Agreement without waiver or modification of any conditions or other requirements that would be material to our opinion, (ii) the Merger will constitute a reorganization within the meaning of Section 368(a) of the Code in which the Company does not recognize income or gain for U.S. federal income tax purposes, (iii)  Parent OP has qualified and at the time of the Asset Contribution will qualify as a partnership for U.S. federal income tax purposes and not as a publicly traded partnership under Section 7704(b) of the Code, (iv) beginning with the date of its formation until the Effective Time of the Merger, Merger Sub, has been and will be disregarded as an entity separate from its owner for U.S. federal income tax purposes, (v) no transaction, agreement or other action has been or will be taken prior to the Effective Time of the Merger pursuant to Section 7.1 or Section 7.2 of the Merger Agreement that causes any representation or covenant in the REIT Certificate (as defined below) to be incorrect or incomplete, (vi) the Company and Parent have complied and will comply with their obligations under Section 7.3 of the Merger Agreement (such that without limitation (A) all steps requested by the Company pursuant Section 7.3(g) of the Merger Agreement in order to ensure that the Asset Contribution does not prevent the Company from qualifying as REIT for its taxable year ending with the Merger are completed prior to the Effective Time, (B) all taxable REIT subsidiary elections contemplated by Section 7.3(h) of the Merger Agreement are made effective not later than the Effective Time and (C) if timely requested by the Company, the election contemplated by Section 7.3(i) is timely made), (vii) in addition to the election contemplated by Section 7.3(i) of the Merger Agreement with respect to investment banker fees, Parent will cause the Company to elect to apply the safe harbor provided in Revenue Procedure 2011-29 with respect to any other fees paid by the Company on or after the Closing that are contingent on the successful closing of the transactions contemplated by the Merger Agreement and otherwise within the scope of such Revenue Procedure, (viii) Parent qualified to be taxed as a REIT under the Code for its taxable year commencing with January 1, 2026 and will continue to satisfy the requirements for qualification and taxation as a REIT under the Code for its taxable year that includes the Merger and for its taxable years thereafter, and (ix) following the Merger, none of Parent, Parent OP and their affiliates shall take any action, or fail to take any action within their control, which would cause the Company to fail to qualify for taxation as a REIT for any Company taxable year.

We also have reviewed and relied upon the representations, statements and covenants of the Company contained in a letter that it provided to us in connection with the preparation of this opinion letter regarding the formation and the prior, current and proposed organization, ownership and operation of the Company and other matters affecting the Company’s ability to qualify as a REIT (such certificate, the “REIT Certificate”).  We assume that each such representation, statement and covenant has been, is, and will be true, correct and complete, that the Company and its subsidiaries have been, are and will be owned and/or operated in accordance with the REIT Certificate (including Parent OP for the period from the Asset Contribution to the Effective Time), and that all representations, statements and covenants that speak to the best of the knowledge and/or belief (or mere belief and/or knowledge) of the Company, or are otherwise qualified as to knowledge, belief or similar qualification, have been, are and will continue to be true, correct and complete as if made without such qualification.  To the extent that the REIT Certificate speaks to the intended or future organization, ownership or operations of the Company, we assume that the Company will in fact be organized, owned and/or operated in accordance with such stated intent.

We express no opinion other than the opinion expressly set forth herein.  Our opinion is not binding on the Internal Revenue Service or a court, and the Internal Revenue Service or a court may disagree with the opinion contained herein.  Although we believe that our opinion will be sustained if challenged, there can be no assurances to this effect.  Furthermore, for purposes of our opinion we have relied solely on the Organizational Documents, the REIT Certificate, the Merger Agreement, the Registration Statement and the assumptions set forth herein.  The Company’s actual qualification as a REIT depends on the Company meeting and having met, in its actual ownership and operations, the applicable asset composition, source of income, shareholder diversification, distribution, record keeping and other requirements of the Code necessary for a corporation to qualify as a REIT.  We have not verified and will not verify the Company’s compliance with those requirements, and no assurance can be given that the actual ownership and operations of the Company and its affiliates have satisfied or will satisfy those requirements or the representations made to us with respect thereto.

This opinion letter speaks only as of the date hereof, and we undertake no obligation to update this opinion letter or to notify any person of any changes in facts, circumstances or applicable law (including without limitation any discovery of any facts that are inconsistent with the REIT Certificate or our assumptions).