Exhibit 5.1

Client: 64901-00052                

December 12, 2014

Berkshire Hathaway Energy Company

666 Grand Avenue, Suite 500

Des Moines, Iowa 50309-2580

Re: Berkshire Hathaway Energy Company

Registration Statement on Form S-4

Ladies and Gentlemen:

We have acted as special counsel to Berkshire Hathaway Energy Company, an Iowa corporation (the “Company”) in connection with the preparation and filing with the Securities and Exchange Commission (the “Commission”) of a Registration Statement on Form S-4, filed on December 12, 2014 (the “Registration Statement”), under the Securities Act of 1933, as amended (the “Securities Act”), and the offering by the Company pursuant thereto of up to $350,000 aggregate principal amount of its 2.40% Senior Notes due 2020 (the “2020 Exchange Notes”), $400,000,000 aggregate principal amount of its 3.50% Senior Notes due 2025 (the “2025 Exchange Notes”) and $750,000,000 aggregate principal amount of its 4.50% Senior Notes due 2045 (the “2045 Exchange Notes” and, together with the 2020 Exchange Notes and the 2025 Exchange Notes, the “Exchange Notes”) in exchange for up to $350,000,000 aggregate principal amount of the Company’s outstanding Senior Notes due 2020 (the “2020 Initial Notes”), $400,000,000 aggregate principal amount of its Senior Notes due 2025 (the “2025 Initial Notes”) and $750,000,000 aggregate principal amount of its Senior Notes due 2045 (the “2045 Initial Notes” and, together with the 2020 Initial Notes and the 2025 Initial Notes, the “Initial Notes”).

The Exchange Notes will be issued pursuant to the Indenture, dated as of October 4, 2002, between the Company and The Bank of New York Mellon Trust Company, N.A., as Trustee (the “Trustee”), as amended by the Second Supplemental Indenture thereto, dated as of May 16, 2003, the Fourth Supplemental Indenture, dated March 24, 2006, the Fifth Supplemental Indenture, dated as of May 11, 2007 (as so amended, the “Base Indenture”), as supplemented with respect to the Initial Notes by the Tenth Supplemental Indenture, dated as of December 4, 2014 (the “Supplemental Indenture”), by and between the Company and the Trustee. The Base Indenture, as supplemented by the Supplemental Indenture, is referred to herein as the “Indenture”.

Brussels — Century City — Dallas — Denver — Dubai — Hong Kong — London — Los Angeles — Munich — New York

Orange County — Palo Alto — Paris — San Francisco — São Paulo — Singapore — Washington, D.C.

Berkshire Hathaway Energy Company

December 12, 2014

Page 2

In arriving at the opinions expressed below, we have examined originals, or copies certified or otherwise identified to our satisfaction as being true and complete copies of the originals, of the Indenture, the Initial Notes and the Exchange Notes, and such other documents, corporate records, certificates of officers of the Company and of public officials and other instruments as we have deemed necessary or advisable to enable us to render these opinions. In our examination, we have assumed, without independent investigation, the genuineness of all signatures, the legal capacity and competency of all natural persons, the authenticity of all documents submitted to us as originals and the conformity to original documents of all documents submitted to us as copies. As to any facts material to these opinions, we have relied to the extent we deemed appropriate and without independent investigation upon statements and representations of officers and other representatives of the Company and others.

Based upon the foregoing, and subject to the assumptions, exceptions, qualifications and limitations set forth herein, we are of the opinion that, when the Exchange Notes are executed and authenticated in accordance with the provisions of the Indenture and issued and delivered in exchange for the Initial Notes in the manner described in the Registration Statement, the Exchange Notes will be legal, valid and binding obligations of the Company, enforceable against the Company in accordance with their respective terms.

The opinions expressed above are subject to the following additional exceptions, qualifications, limitations and assumptions:

A. We render no opinion herein as to matters involving the laws of any jurisdiction other than the State of New York. This opinion is limited to the effect of the current state of the laws of the State of New York and the facts as they currently exist. We assume no obligation to revise or supplement this opinion in the event of future changes in such laws or the interpretations thereof or such facts after such time as the Registration Statement is declared effective.

B. Our opinions above are each subject to (i) the effect of any bankruptcy, insolvency, reorganization, moratorium, arrangement or similar laws affecting the rights and remedies of creditors’ generally, including without limitation the effect of statutory or other laws regarding fraudulent transfers or preferential transfers and (ii) general principles of equity, including without limitation concepts of materiality, reasonableness, good faith and fair dealing and the possible unavailability of specific performance, injunctive relief or other equitable remedies regardless of whether enforceability is considered in a proceeding in equity or at law.

C. We express no opinion regarding the effectiveness of (i) any waiver of stay, extension or usury laws; (ii) provisions relating to indemnification, exculpation or contribution, to the extent such provisions may be held unenforceable as contrary to public

Berkshire Hathaway Energy Company

December 12, 2014

Page 3

policy or federal or state securities laws or due to the negligence or willful misconduct of the indemnified party; (iii) any provision waiving the right to object to venue in any court; (iv) any agreement to submit to the jurisdiction of any Federal court; (v) any waiver of the right to jury trial or (vi) any provision to the effect that every right or remedy is cumulative and may be exercised in addition to any other right or remedy or that the election of some particular remedy does not preclude recourse to one or more others.

We consent to the filing of this opinion as an exhibit to the Registration Statement, and we further consent to the use of our name under the caption “Legal Matters” in the Registration Statement and the prospectus that forms a part thereof. In giving these consents, we do not thereby admit that we are within the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations of the Commission promulgated thereunder.

Very truly yours,

/s/ GIBSON, DUNN & CRUTCHER LLP