Exhibit 99.1

THIRD AMENDING AGREEMENT RE: FOURTH AMENDED AND RESTATED CREDIT AGREEMENT

THIS THIRD AMENDING AGREEMENT made as of the 7th day of May, 2025 (this “Amendment”).

BETWEEN:

THE BANK OF NOVA SCOTIA,
a Canadian chartered bank

(herein, in its capacity as administrative agent of the Lenders, called the “Agent”)

– and –

THE BANK OF NOVA SCOTIA,
CANADIAN IMPERIAL BANK OF COMMERCE,
ROYAL BANK OF CANADA,
BANK OF MONTREAL,
THE TORONTO-DOMINION BANK,
NATIONAL BANK OF CANADA,
MUFG BANK, LTD., CANADA BRANCH,
BANK OF AMERICA, N.A., CANADA BRANCH,
MORGAN STANLEY BANK, N.A.,
FÉDÉRATION DES CAISSES DESJARDINS DU QUÉBEC and
WELLS FARGO BANK, N.A., CANADIAN BRANCH

(herein, in their capacities as lenders to the Borrower, collectively called the “Lenders” and individually called a “Lender”)

– and –

FORTIS INC.,

a corporation existing under the laws of the Province of Newfoundland and Labrador

(herein called the “Borrower”)

WHEREAS pursuant to a fourth amended and restated credit agreement made as of May 4, 2022 among the Borrower, the Agent and the Lenders (as amended by a first amending agreement dated May 4, 2023 and a second amending agreement dated June 6, 2024, the “Existing Credit Agreement”), the Lenders established a certain credit facility in favour of the Borrower on the terms and conditions set forth therein; All capitalized terms which are used herein without being specifically defined herein shall have the meaning ascribed thereto in the Existing Credit Agreement as amended hereby (as so amended, the “Credit Agreement”).

AND WHEREAS the parties hereto wish to amend certain provisions of the Existing Credit Agreement.

NOW THEREFORE THIS AMENDMENT WITNESSES that, in consideration of the mutual covenants and agreements contained herein (the receipt and sufficiency of which is hereby acknowledged), the parties hereto covenant and agree as follows:

ARTICLE 1 DEFINED TERMS

ARTICLE 2 AMENDMENTS

Subject to the terms and conditions herein contained, the Existing Credit Agreement is hereby amended to the extent necessary to give effect to the provisions of this Amendment and to incorporate the provisions of this Amendment into the Existing Credit Agreement.

““Adjusted Term SOFR Rate” means:

provided that, in each case, if the Adjusted Term SOFR Rate as so determined would be less than the Floor, such rate shall be deemed to be equal to the Floor for the purposes of this Agreement.”

“(a)      with respect to any Term Benchmark Loan, the period commencing on the date of such Term Benchmark Loan and ending on the numerically corresponding day in the calendar month that is one (1), three (3) or six (6) months or a SOFR Non-Standard Interest Period as the Agent may agree to (in each case, subject to the availability thereof), as the Borrower may elect; provided, that (i) if any Interest Period would end on a day other than a Business Day, such Interest Period shall be extended to the next succeeding Business Day unless such next succeeding Business Day would fall in the next calendar month, in which case such Interest Period shall end on the next preceding Business Day, (ii) any Interest Period that commences on the last Business Day of a calendar month (or on a day for which there is no numerically corresponding day in the last calendar month of such Interest Period) shall end on the last Business Day of the last calendar month of such Interest Period and (iii) no tenor that has been removed from this definition pursuant to clause (e) of Section 1.17 shall be available for specification in any request for a Term Benchmark Loan or rollover of, or conversion into, a Term Benchmark Loan. For purposes hereof, the date of a Term Benchmark Loan initially shall be the date on which such Term Benchmark Loan is made and thereafter shall be the effective date of the most recent conversion or rollover of such Term Benchmark Loan;”

““Term SOFR Rate” means, with respect to any Term Benchmark Loan for a SOFR Standard Interest Period and for any tenor comparable to the applicable SOFR Standard Interest Period, the Term SOFR Reference Rate at approximately 5:00 a.m. New York time two Business Days prior to the commencement of such tenor comparable to the applicable Interest Period, as such rate is published by the Term SOFR Administrator.”

““SOFR Interpolated Rate” means, for any Term Benchmark Loan for a SOFR Non-Standard Interest Period, the rate per annum determined by the Agent (which determination shall be conclusive and binding absent manifest error) to be equal to the rate that results from interpolating on a linear basis between: (a) (i) Term SOFR Rate for the longest SOFR Standard Interest Period for which the Term SOFR Rate is available that is shorter than the SOFR Non-Standard Interest Period of such Term Benchmark Loan plus (ii) the Term SOFR Adjustment applicable to such SOFR Standard Interest Period and (b) (i) the Term SOFR Rate, for the shortest SOFR Standard Interest Period for which the Term SOFR Rate is available that exceeds the SOFR Non-Standard Interest Period of such Term Benchmark Loan, plus (ii) the Term SOFR Adjustment applicable to such SOFR Standard Interest Period, in each case, at such time; provided that when determining the SOFR Interpolated Rate for a SOFR Non-Standard Interest Period which is less than one (1) month, the SOFR Interpolated Rate shall be deemed to be the Term SOFR Rate for a SOFR Standard Interest Period of one (1) month’s duration plus the Term SOFR Adjustment applicable to such SOFR Standard Interest Period.

“SOFR Non-Standard Interest Period” means with respect to a Term Benchmark Loan, an Interest Period which is for a term other than one (1) month, three (3) months or six (6) months and which such Term Benchmark Loan shall bear interest at the SOFR Interpolated Rate.

“SOFR Standard Interest Period” means, with respect to a Term Benchmark Loan, an Interest Period which is for a term of one (1) month, three (3) months or six (6) months.”

“(i)      Interest Periods for Term Benchmark Loans shall have a duration of one (1) month, three (3) months or six (6) months or a SOFR Non-Standard Interest Period as the Agent may agree to, subject to availability, provided that in the event the Borrower fails to specify an Interest Period for any Term Benchmark Loan in the applicable Drawdown Notice, Conversion Notice or Rollover Notice, the Borrower shall be deemed to have selected an Interest Period of one month;”

ARTICLE 3 REPRESENTATIONS AND WARRANTIES

To induce the Lenders and the Agent to enter into this Amendment, the Borrower hereby represents and warrants to the Lenders and the Agent that:

The representations and warranties in this Section 3.1 are given solely as of the date of this Amendment and the provisions of Section 12.1(c) of the Existing Credit Agreement do not apply to the representations and warranties in this Section 3.1.

ARTICLE 4 CONDITIONS PRECEDENT TO EFFECTIVENESS OF AMENDMENT

This Amendment shall not become effective until the date on which the following conditions precedent are fulfilled:

ARTICLE 5 FEES

On the execution and delivery of this Amendment, the Borrower shall pay to the Agent for the account of the Lenders an extension fee of 3.5 basis points per annum on the Individual Commitment of each Lender, calculated for the period commencing on and including the Maturity Date (as defined in the Existing Credit Agreement) and ending on and including the first day immediately preceding the Maturity Date, the entirety of which extension fee shall be due and payable upon execution of this Amendment and which such extension fee shall be non-refundable and fully earned when due.

ARTICLE 6 MISCELLANEOUS

On and after the date of this Amendment, each reference in the Existing Credit Agreement to “this Agreement”, “hereunder”, “hereof”, or words of like import referring to the Existing Credit Agreement and each reference in any related document to the “Credit Agreement”, “thereunder”, “thereof”, or words of like import referring to the Existing Credit Agreement, shall mean and be a reference to the Existing Credit Agreement as amended hereby. The Existing Credit Agreement, as amended hereby, is and shall continue to be in full force and effect and is hereby in all respects ratified and confirmed.

This Amendment shall be governed by and construed in accordance with the Laws of the Province of Ontario and the federal Laws of Canada applicable therein.

This Amendment shall enure to the benefit of and shall be binding upon the parties hereto and their respective successors and permitted assigns.

If any provision of this Amendment is inconsistent or conflicts with any provision of the Existing Credit Agreement, the relevant provision of this Amendment shall prevail and be paramount.

The Borrower shall do, execute and deliver or shall cause to be done, executed and delivered all such further acts, documents and things as the Agent may reasonably request for the purpose of giving effect to this Amendment and to each and every provision hereof.

The execution, delivery and effectiveness of this Amendment shall not, except as expressly provided herein, operate as a waiver of any right, power or remedy of any Lender or the Agent under any of the Loan Documents, nor constitute a waiver of any provision of any of the Loan Documents.

This Amendment may be executed in one or more counterparts, each of which shall be deemed to be an original and all of which taken together shall be deemed to constitute one and the same instrument. Delivery of an executed signature page of this Amendment by e-mail in pdf format shall be as effective as delivery of a manually executed counterpart thereof. The words “execution”, “signed”, “signature” and words of like import in this Amendment shall be deemed to include electronic signatures or the keeping of records in electronic form, each of which shall be of the same legal effect, validity or enforceability as a manually executed signature or the use of a paper-based recordkeeping system, as the case may be, to the extent and as provided for in any applicable law.

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IN WITNESS WHEREOF the parties hereto have executed and delivered this Amendment on the date first above written.