6-K

SECURITIES AND EXCHANGECOMMISSION

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 2025

Commission File Number: 333-225519-01

HYDRO ONE LIMITED

(Translation of Registrant’s name into English)

483 Bay Street, South Tower, 8th Floor, Toronto Ontario M5G 2P5 Canada

(Address of principal executive offices)

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 ☒

SIGNATURE

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.

EXHIBIT INDEX

EX-99.1

Exhibit 99.1

Hydro One and the Power Workers’ Union reach tentative agreements

Toronto, May 5, 2025 – Hydro One Inc. (Hydro One) and the Power Workers’ Union (PWU) are pleased to announce that tentative agreements have been reached for the two collective agreements covering employees in front-line roles across the company’s operations in Ontario. Both tentative agreements remain subject to ratification by the PWU membership.

Negotiations covered the renewal of two collective agreements: the main collective agreement and the Customer Service Operations collective agreement.

PWU members will vote on these agreements and once ratified, these agreements will be effective October 1, 2025.

Hydro One Limited (TSX: H)

Hydro One Limited, through its wholly-owned subsidiaries, is Ontario’s largest electricity transmission and distribution provider with 1.5 million valued customers, $36.7 billion in assets as at December 31, 2024, and annual revenues in 2024 of approximately $8.5 billion.

Our team of 10,100 skilled and dedicated employees proudly build and maintain a safe and reliable electricity system which is essential to supporting strong and successful communities. In 2024, Hydro One invested $3.1 billion in its transmission and distribution networks, and supported the economy through buying $2.9 billion of goods and services.

We are committed to the communities where we live and work through community investment, sustainability and diversity initiatives.

Hydro One Limited’s common shares are listed on the TSX and certain of Hydro One Inc.’s medium term notes are listed on the NYSE. Additional information can be accessed at www.hydroone.com, www.sedarplus.com or www.sec.gov.

Forward-Looking Statements and Information:

This press release may contain “forward-looking information” within the meaning of applicable Canadian securities laws and “forward-looking statements” within the meaning of applicable U.S. securities laws (collectively, “forward-looking information”). Statements containing forward-looking information are made pursuant to the “safe harbour” provisions of applicable Canadian and U.S. securities laws. Words such as “expect”, “anticipate”, “intend”, “attempt”, “may”, “plan”, “will”, “can”, “believe”, “seek”, “estimate”, and variations of such words and similar expressions are intended to identify such forward-looking information. These statements are not guarantees of future performance or actions and involve assumptions and risks and uncertainties that are difficult to predict. Therefore, actual outcomes and results may differ materially from

what is expressed, implied or forecasted in such forward-looking information. Some of the factors that could cause actual results or outcomes to differ materially from the results expressed, implied or forecasted by such forward-looking information, including some of the assumptions used in making such statements, are discussed more fully in Hydro One’s filings with the securities regulatory authorities in Canada, which are available on SEDAR+ at www.sedarplus.com. Hydro One does not intend, and it disclaims any obligation, to update any forward-looking information, except as required by law.

For More Information

For more information about everything Hydro One, please visit www.hydroone.com where you can find additional information including links to securities filings, historical financial reports, and information about the Company’s governance practices, corporate social responsibility, customer solutions, and further information about its business.

Please contact Hydro One Media Relations 24 hours a day at 1-877-506-7584 (toll-free in Ontario only) or 416-345-6868