EXHIBIT 4.1

NORTHEAST UTILITIES

and

THE BANK OF NEW YORK MELLON TRUST COMPANY, N.A., AS TRUSTEE

FOURTH SUPPLEMENTAL INDENTURE

Dated as of March 15, 2012

Supplemental to the Indenture dated as of April 1, 2002

Floating Rate Senior Notes, Series D, Due 2013

FOURTH SUPPLEMENTAL INDENTURE, dated as of March 15, 2012 (this “Fourth Supplemental Indenture”), between NORTHEAST UTILITIES, a voluntary association duly organized and existing under the laws of the Commonwealth of Massachusetts (the “Company”), and THE BANK OF NEW YORK MELLON TRUST COMPANY, N.A., formerly known as The Bank of New York Trust Company, N.A. (as successor trustee to The Bank of New York), a national banking association, as Trustee under the Original Indenture referred to below (the “Trustee”).

RECITALS OF THE COMPANY

The Company has heretofore executed and delivered to the Trustee an indenture dated as of April 1, 2002 (the “Original Indenture”), as supplemented and amended, to provide for the issuance from time to time of its notes, debentures or other evidences of indebtedness (the “Securities”), the form and terms of which are to be established as set forth in Sections 201 and 301 of the Original Indenture.

Section 901 of the Original Indenture provides, among other things, that the Company and the Trustee may enter into indentures supplemental to the Original Indenture for, among other things, (a) the purpose of establishing the form and terms of the Securities of any series as permitted by Sections 201 and 301 of the Original Indenture, (b) changing any of the provisions of the Original Indenture as they apply to any series of Securities created by such supplemental indenture and (c) amending the Original Indenture in a manner not materially adverse to Holders.

The Company has heretofore executed and delivered to the Trustee the following Supplemental Indentures for the purpose of creating the following series of Securities:

The Company desires to create a new series of Securities, in an initial aggregate principal amount of $300,000,000, to be designated the “Floating Rate Senior Notes, Series D, Due 2013” (the “Notes”), and all action on the part of the Company necessary to authorize the issuance of the Notes under the Original Indenture and this Fourth Supplemental Indenture has been duly taken.

All acts and things necessary to make the Notes, when executed by the Company and completed, authenticated and delivered by the Trustee as provided in the Original Indenture and this Fourth Supplemental Indenture, the valid and binding obligations of the Company and to constitute these presents a valid and binding supplemental indenture and agreement according to its terms, have been done and performed.

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NOW, THEREFORE, THIS FOURTH SUPPLEMENTAL INDENTURE WITNESSETH:

That in consideration of the premises and of the acceptance and purchase of the Notes by the Holders thereof and of the acceptance of this trust by the Trustee, the Company covenants and agrees with the Trustee, for the equal and ratable benefit of the Holders of the Notes, as follows:

ARTICLE ONE

Definitions

The use of the terms and expressions herein is in accordance with the definitions, uses and constructions contained in the Original Indenture and form of the Notes attached hereto as Exhibit A.

ARTICLE TWO

Terms and Issuance of the Floating Rate Senior Notes, Series D, Due 2013

SECTION 201. Issue of Notes.

A series of Securities which shall be designated the “Floating Rate Senior Notes, Series D, Due 2013” shall be executed, authenticated and delivered from time to time in accordance with the provisions of, and shall in all respects be subject to, the terms and conditions and covenants of, the Original Indenture and this Fourth Supplemental Indenture (including the form of Note attached hereto as Exhibit A). The aggregate principal amount of the Notes that will initially be authenticated and delivered under this Fourth Supplemental Indenture shall not, except as permitted by the provisions of the Original Indenture, exceed $300,000,000. Additional Notes, without limitation as to amount, having substantially the same terms as the Notes (except a different issue date, issue price and bearing interest from the last Interest Payment Date to which interest has been paid or duly provided for on the Outstanding Notes, and, if no interest has been paid, from March 22, 2012) may also be issued by the Company pursuant to this Fourth Supplemental Indenture without the consent of the existing Holders of the Notes, provided that an Event of Default has not occurred and is continuing with respect to the Notes. Such additional Notes shall be consolidated and form a part of the same series as the outstanding Notes.

SECTION 202. Form of Notes; Incorporation of Terms.

The Notes shall be in substantially the form set forth in Exhibit A attached hereto. The terms of the Notes contained in such form are hereby incorporated herein by reference and are made a part of this Fourth Supplemental Indenture.

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SECTION 203. Global Security; Depositary for Global Securities.

The Notes shall be issued initially in the form of a Global Security. The Depositary for any Global Securities of the series of which the Notes are a part shall be The Depository Trust Company, New York, New York.

SECTION 204. Limitation on Liens.

The provisions of Section 1007 of the Original Indenture shall be applicable to the Notes.

SECTION 205. Sale and Leaseback Transactions.

The provisions of Section 1012 of the Original Indenture shall be applicable to the Notes.

SECTION 206. Place of Payment.

The Place of Payment in respect of the Notes shall be at the Corporate Trust Office, which, at the date hereof, is located at 525 William Penn Place, 38th Floor, Pittsburgh, Pennsylvania 15259, Attention: Corporate Trust Administration.

SECTION 207. Section 401 of the Original Indenture.

Section 401 of the Original Indenture shall not apply to the Notes. Section 401 of the Original Indenture is hereby amended in its entirety with respect to the Notes to state:

“SECTION 401. Satisfaction and Discharge of Indenture.

This Indenture shall upon Company Request cease to be of further effect, and the Trustee, at the expense of the Company, shall execute proper instruments acknowledging satisfaction and discharge of this Indenture, when

(1) either (A) all Securities theretofore authenticated and delivered (other than (x) Securities which have been destroyed, lost or stolen and which have been replaced or paid as provided in Section 306 hereof and (y) Securities for whose payment money has theretofore been deposited in trust or segregated and held in trust by the Company and thereafter repaid to the Company or discharged from such trust, as provided in Section 1003 hereof) have been delivered to the Trustee for cancellation; or

(B) all such Securities not theretofore delivered to the Trustee for cancellation have become due and payable and the Company has irrevocably deposited or caused to be irrevocably deposited (in each case except as provided in Section 402(c) hereof and the last paragraph of Section 1003 hereof) with the Paying Agent or with the Trustee as trust funds in trust for the purpose an amount of money sufficient to pay and discharge, or has otherwise paid, the entire Indebtedness on such Securities for principal and interest, if any;

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(2) the Company has paid or caused to be paid all other sums payable hereunder by the Company; and

(3) the Company has delivered to the Trustee an Officers’ Certificate and an Opinion of Counsel, each stating that all conditions precedent herein provided for relating to the satisfaction and discharge of this Indenture have been complied with;

provided, however, that if the Trustee or any Paying Agent is required to return any money deposited with it as described in this Section 401 to the Company or its representative under any applicable Federal or state bankruptcy, insolvency or similar law, this Indenture shall retroactively be deemed not to have been satisfied and discharged and automatically shall be reinstated and shall remain in full force and effect without any further action, but the Company shall execute and deliver such instruments as the Trustee shall reasonably request to evidence and acknowledge the same.

Notwithstanding the satisfaction and discharge of this Indenture, the obligations of the Company to the Trustee under Section 607 hereof, the obligations of the Trustee to any Authenticating Agent under Section 614 hereof and, if money shall have been deposited with the Paying Agent or the Trustee pursuant to subclause (B) of clause (1) of this Section 401, the obligations of the Company and the Trustee under Sections 401, 402, 1002 and 1003 hereof shall survive.”

SECTION 208. Section 403 of the Original Indenture.

Section 403 of the Original Indenture shall not apply to the Notes. Section 403 of the Original Indenture is hereby amended in its entirety with respect to the Notes to state:

“SECTION 403. Satisfaction, Discharge and Defeasance of the Notes.

The Company shall be deemed to have paid and Discharged the entire Indebtedness on all the Outstanding Notes upon the deposit referred to in subparagraph (1) hereof, and the provisions of this Indenture, as they relate to such Outstanding Notes, shall no longer be in effect (and the Trustee, at the expense of the Company, shall at Company Request execute proper instruments acknowledging the same), except as to:

(a) the rights of Holders of the Notes to receive, from the trust funds described in subparagraph (1) hereof, payment of the principal of (and premium, if any) or interest, if any, on the Outstanding Notes on the Stated Maturity; or to and including the Redemption Date irrevocably designated by the Company pursuant to subparagraph (4) hereof;

(b) the Company’s obligations with respect to such Notes under Sections 305, 306, 1002 and 1003 hereof and, if the Company shall have irrevocably designated a Redemption Date pursuant to subparagraph (5) hereof, Sections 1101, 1104 and 1106 hereof as they apply to such Redemption Date;

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(c) the Company’s obligations with respect to the Trustee under Section 607 hereof; and

(d) the rights, powers, trust and immunities of the Trustee hereunder and the duties of the Trustee under Section 402 hereof and, if the Company shall have irrevocably designated a Redemption Date pursuant to subparagraph (5) hereof, Article 11 and the duty of the Trustee to authenticate Notes on registration of transfer or exchange;

provided that, the following conditions shall have been satisfied:

(1) the Company has irrevocably deposited or caused to be irrevocably deposited (in each case except as provided in Section 402(c) hereof and the last paragraph of Section 1003 hereof) with the Trustee as trust funds in trust, specifically pledged as security for, and dedicated solely to, the benefit of the Holders of the Notes, an amount of (i) money, or (ii) U.S. Government Obligations or a combination of money and U.S. Government Obligations, in each case sufficient, in the opinion of a nationally recognized firm of independent certified public accountants expressed in a written certification thereof delivered to the Trustee, to pay and discharge, and which the Trustee shall be instructed to apply to pay and discharge, the principal of and interest, if any, on the Notes on the Stated Maturity or to and including the Redemption Date irrevocably designated by the Company pursuant to subparagraph (4) hereof; provided, however, that (A) all money and U.S. Government Obligations deposited pursuant to this Section 403 shall be denominated in U.S. Dollars; and (B) U.S. Government Obligations shall be valued at the amount of money that they will provide through the payment of principal and interest in respect thereof in accordance with their terms no later than one day prior to the Stated Maturity or such Redemption Date, and shall not contain provisions permitting the redemption or other prepayment at the option of the issuer thereof prior to the Stated Maturity or such Redemption Date;

(2) no Event of Default or event which with notice or lapse of time would become an Event of Default (including by reason of such deposit) with respect to the Notes shall have occurred and be continuing on the date of such deposit;

(3) the Company has delivered to the Trustee an unqualified opinion, in form and substance reasonably acceptable to the Trustee, of independent counsel of national standing selected by the Company and satisfactory to the Trustee to the effect that (i) Holders of the Notes will not recognize income, gain or loss for Federal income tax purposes as a

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result of the deposit, defeasance and discharge, which opinion shall be based on a change in law or a ruling by the U.S. Internal Revenue Service after the date hereof and (ii) the defeasance trust is not, or is registered as, an investment company under the Investment Company Act of 1940;

(4) if the Company has deposited or caused to be deposited money or U.S. Government Obligations to pay or discharge the principal of (and premium, if any) and interest, if any, on the Outstanding Securities of a series to and including a Redemption Date on which all of the Outstanding Securities of such series are to be redeemed, such Redemption Date shall be irrevocably designated by a Board Resolution delivered to the Trustee on or prior to the date of deposit of such money or U.S. Government Obligations, and such Board Resolution shall be accompanied by an irrevocable Company Request that the Trustee give notice of such redemption in the name and at the expense of the Company not less than 30 nor more than 60 days prior to such Redemption Date in accordance with Section 1104 hereof;

(5) the Company has delivered to the Trustee an Officers’ Certificate and an Opinion of Counsel, each stating that all conditions precedent herein provided for relating to the satisfaction and discharge of the Securities have been complied with.

The condition set forth in clause (i) of subparagraph (3) hereof shall not apply if the Company shall have complied with the remaining conditions of subparagraphs 1-5 hereof as of a date which is no less than 60 days prior to the maturity date.

Anything herein to the contrary notwithstanding, (a) if the Trustee or any Paying Agent is required to return any money or U.S. Government Obligations deposited with it pursuant to this Section 403 to the Company or its representative under any Federal or state bankruptcy, insolvency or similar law, such Security shall thereupon be deemed retroactively not to have been paid and any satisfaction and discharge of the Company’s Indebtedness in respect thereof shall retroactively be deemed not to have been effected, and such Security shall be deemed to remain Outstanding and the provisions of the Indenture relating to such Security shall be reinstated and shall remain in full force and effect and (b) any satisfaction and discharge of the Company’s Indebtedness in respect of any Security shall be subject to the provisions of the last paragraph of Section 1003.”

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SECTION 209. Section 1009 of the Original Indenture.

Subparagraph (i) of Section 1009 of the Original Indenture shall not apply to the Notes. Subparagraph (i) of Section 1009 of the Original Indenture is hereby amended in its entirety with respect to the Notes to state:

“the Company has irrevocably deposited or caused to be irrevocably deposited (in each case except as provided in Section 402(c) hereof and the last paragraph of Section 1003 hereof) with the Trustee (specifying that each deposit is pursuant to this Section 1009) as trust funds in trust, specifically pledged as security for, and dedicated solely to, the benefit of the Holders of the Notes, an amount of (i) money or (ii) U.S. Government Obligations or a combination of money and U.S. Government Obligations, in each case sufficient, in the opinion of a nationally recognized firm of independent certified public accountants expressed in a written certification thereof delivered to the Trustee, to pay and discharge, and which the Trustee shall be instructed to apply to pay and discharge, the principal of and each installment of principal and interest, if any, on the Notes on the Stated Maturity of such principal or to and including the Redemption Date irrevocably designated by the Company pursuant to subparagraph (4) of this Section 1009; provided, however, that (A) all money and U.S. Government Obligations deposited pursuant to this Section 1009 shall be denominated in U.S. Dollars; and (B) U.S. Government Obligations shall be valued at the amount of money that they will provide through the payment of principal and interest in respect thereof in accordance with their terms no later than one day prior to the Stated Maturity or such Redemption Date and shall not contain provisions permitting the redemption or other prepayment at the option of the issuer thereof prior to the Stated Maturity;”

ARTICLE THREE

Amendment of Original Indenture

SECTION 301. Amendment to Section 105 of the Original Indenture.

Section 105 of the Original Indenture is amended by adding the following paragraph at the end of Section 105:

“In addition to the foregoing, the Trustee agrees to accept and act upon notice, instructions or directions pursuant to this Indenture sent by unsecured e-mail, facsimile transmission or other similar unsecured electronic methods. If the party elects to give the Trustee e-mail or facsimile instructions (or instructions by a similar electronic method) and the Trustee in its discretion elects to act upon such instructions, the Trustee’s understanding of such instructions shall be deemed controlling. The Trustee shall not be liable for any losses, costs or expenses arising directly or indirectly from the Trustee’s reliance upon and compliance with such instructions notwithstanding such instructions conflict or are inconsistent with a subsequent written instruction. The party providing electronic instructions agrees to assume all risks arising out of the use of such electronic methods to submit instructions and directions to the Trustee, including without limitation the risk of the Trustee acting on unauthorized instructions, and the risk or interception and misuse by third parties.”

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SECTION 302. Amendment of the Original Indenture by Adding Section 115 Thereto.

The Original Indenture is amended by adding the following Section 115:

“SECTION 115. Submission of Jurisdiction; Waiver of Jury Trial.

TO THE FULLEST EXTENT PERMITTED BY APPLICABLE LAW, EACH OF THE COMPANY AND THE TRUSTEE HEREBY IRREVOCABLY SUBMITS TO THE JURISDICTION OF ANY NEW YORK STATE COURT SITTING IN THE BOROUGH OF MANHATTAN IN THE CITY OF NEW YORK OR ANY FEDERAL COURT SITTING IN THE BOROUGH OF MANHATTAN IN THE CITY OF NEW YORK IN RESPECT OF ANY SUIT, ACTION OR PROCEEDING ARISING OUT OF OR RELATING TO THIS INDENTURE AND THE SECURITIES, AND IRREVOCABLY ACCEPTS FOR ITSELF AND IN RESPECT OF ITS PROPERTY, GENERALLY AND UNCONDITIONALLY, JURISDICTION OF THE AFORESAID COURTS. EACH OF THE COMPANY AND THE TRUSTEE HEREBY IRREVOCABLY WAIVES, TO THE FULLEST EXTENT PERMITTED BY APPLICABLE LAW, ANY AND ALL RIGHT TO TRIAL BY JURY IN ANY LEGAL PROCEEDING ARISING OUT OF OR RELATING TO THIS INDENTURE, THE SECURITIES OR THE TRANSACTION CONTEMPLATED HEREBY.”

SECTION 303. Amendment to 603 of the Original Indenture.

Section 603 of the Original Indenture is hereby amended by deleting “and” at the end of Section 603(g) thereto, deleting the period at the end of Section 603(h) thereto, and adding “;” at the end of such Section 603(h). Further, Section 603 of the Original Indenture is amended by adding the following clauses at the end of Section 603 of the Indenture:

“ (i) the Trustee shall not be liable for any action taken, suffered, or omitted to be taken by it in good faith and reasonably believed by it to be authorized or within the discretion or rights or powers conferred upon it by this Indenture;

(j) in no event shall the Trustee be responsible or liable for special, indirect, or consequential loss or damage of any kind whatsoever (including, but not limited to, loss of profit) irrespective of whether the Trustee has been advised of the likelihood of such loss or damage and regardless of the form of action; and

(k) in no event shall the Trustee be responsible or liable for any failure or delay in the performance of its obligations hereunder arising out of or caused by, directly or indirectly, forces beyond its control, including, without limitation, strikes, work stoppages, accidents, acts of war or terrorism, civil or military disturbances, nuclear or natural catastrophes or acts of God, and interruptions, loss or malfunctions of utilities, communications or computer (software and hardware) services.”

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SECTION 304. Except as provided in Sections 301, 302 and 303 hereof, each and every term and condition contained in this Fourth Supplemental Indenture that modifies, amends or supplements the terms and conditions of the Original Indenture shall apply only to Notes established hereby and not to any other Securities established under the Original Indenture. Except as specifically amended and supplemented by, or to the extent inconsistent with, this Fourth Supplemental Indenture, the Original Indenture shall remain in full force and effect and is hereby ratified and confirmed.

ARTICLE FOUR

Miscellaneous

SECTION 401. Execution as Supplemental Indenture.

This Fourth Supplemental Indenture is executed and shall be construed as an indenture supplemental to the Original Indenture and, as provided in the Original Indenture, this Fourth Supplemental Indenture forms a part thereof.

SECTION 402. Conflict with Trust Indenture Act.

If any provision hereof limits, qualifies or conflicts with another provision hereof which is required to be included in this Fourth Supplemental Indenture by any of the provisions of the Trust Indenture Act, such required provision shall control.

SECTION 403. Effect of Headings.

The Article and Section headings herein are for convenience only and shall not affect the construction hereof.

SECTION 404. Successors and Assigns.

All covenants and agreements by the Company in this Fourth Supplemental Indenture shall bind its successors and assigns, whether so expressed or not.

SECTION 405. Separability Clause.

In case any provision in this Fourth Supplemental Indenture or in the Notes shall be invalid, illegal or unenforceable, the validity, legality and enforceability of the remaining provisions shall not in any way be affected or impaired thereby.

SECTION 406. Benefits of Fourth Supplemental Indenture.

Nothing in this Fourth Supplemental Indenture or in the Notes, express or implied, shall give to any Person, other than the parties hereto and their successors hereunder and the Holders, any benefit or any legal or equitable right, remedy or claim under this Fourth Supplemental Indenture.

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SECTION 407. Recitals.

The Trustee shall have no responsibility for the recitals contained in this Fourth Supplemental Indenture, all of which shall be taken as the statements of the Company, or for the validity or sufficiency of this Fourth Supplemental Indenture.

SECTION 408. Governing Law.

This Fourth Supplemental Indenture shall be governed by and construed in accordance with the laws of the State of New York.

SECTION 409. Execution and Counterparts.

This Fourth Supplemental Indenture may be executed in any number of counterparts, each of which shall be deemed to be an original, but all such counterparts shall together constitute but one and the same instrument.

SECTION 410. Liability of Trustees and Shareholders.

The Declaration of Trust of the Company provides that no shareholder of the Company shall be held to any liability whatever for the payment of any sum of money, or for damages or otherwise under any contract, obligation or undertaking made, entered into or issued by the trustees of the Company or by any officer, agent or representative elected or appointed by the trustees and no such contract, obligation or undertaking shall be enforceable against the trustees or any of them in their or his individual capacities or capacity and all such contracts, obligations and undertakings shall be enforceable only against the trustees as such, and every person, firm, association, trust and corporation having any claim or demand arising out of any such contract, obligation or undertaking shall look only to the trust estate for the payment or satisfaction thereof.

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IN WITNESS WHEREOF, the parties hereto have caused this Fourth Supplemental Indenture to be duly executed, all as of the day and year first above written.

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EXHIBIT 4

EXHIBIT A

[Form of Face of Global Security]

THIS SECURITY IS A GLOBAL SECURITY WITHIN THE MEANING OF THE INDENTURE HEREINAFTER REFERRED TO AND IS REGISTERED IN THE NAME OF A DEPOSITARY OR A NOMINEE OF A DEPOSITARY. THIS SECURITY IS EXCHANGEABLE FOR SECURITIES REGISTERED IN THE NAME OF A PERSON OTHER THAN THE DEPOSITARY OR ITS NOMINEE ONLY IN THE LIMITED CIRCUMSTANCES DESCRIBED IN THE INDENTURE, AND NO TRANSFER OF THIS SECURITY (OTHER THAN A TRANSFER OF THIS SECURITY AS A WHOLE BY THE DEPOSITARY TO A NOMINEE OF THE DEPOSITARY OR BY A NOMINEE OF THE DEPOSITARY TO THE DEPOSITARY OR ANOTHER NOMINEE OF THE DEPOSITARY) MAY BE REGISTERED EXCEPT IN LIMITED CIRCUMSTANCES.

Unless this certificate is presented by an authorized representative of The Depository Trust Company, a New York corporation (“DTC”), to Northeast Utilities or its agent for registration of transfer, exchange, or payment, and any certificate issued is registered in the name of Cede & Co. or in such other name as is requested by an authorized representative of DTC (and any payment is made to Cede & Co. or to such other entity as is requested by an authorized representative of DTC), ANY TRANSFER, PLEDGE, OR OTHER USE HEREOF FOR VALUE OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL inasmuch as the registered owner hereof, Cede & Co., has an interest herein.

NORTHEAST UTILITIES

FLOATING RATE SENIOR NOTES, SERIES D, DUE 2013

No. 1

NORTHEAST UTILITIES, a voluntary association duly organized and existing under the laws of the Commonwealth of Massachusetts (the “Company,” which term includes any successor entity under the Indenture hereinafter referred to), for value received, hereby promises to pay to Cede & Co., or registered assigns, the principal sum of Three Hundred Million Dollars ($300,000,000.00) on September 20, 2013 (the “Final Maturity”), and to pay interest thereon from the date of original issuance of the Notes or from the most recent Interest Payment Date to which interest has been paid or duly provided for, quarterly in arrears, on March 20, June 20, September 20 and December 20 of each year (each, an “Interest Payment Date”), and on Final Maturity, commencing June 20, 2012, at a rate equal to LIBOR (as defined below) plus 0.75%, until the principal hereof is paid or made available for payment and, subject to the terms of the Indenture, at the same rate on any overdue principal and (to the extent that the payment of such interest shall be legally enforceable) on any overdue installment of interest.

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If any of the Interest Payment Dates (other than the Final Maturity) falls on a day that is not a Business Day (as defined below), the Interest Payment Date will be the next succeeding Business Day unless that Business Day is in the next succeeding calendar month, in which case the Interest Payment Date will be the immediately preceding Business Day. If the Final Maturity falls on a day that is not a Business Day, the payment of principal and interest will be made on the next succeeding Business Day, and no interest on such payment shall accrue for the period from and after the Final Maturity.

Interest on this Security will accrue from, and including, March 22, 2012, to, and excluding, the first Interest Payment Date and then from, and including, the immediately preceding Interest Payment Date to which interest has been paid or duly provided for to, but excluding, the next Interest Payment Date or the Final Maturity, as the case may be. Interest on this Security will be computed on the basis of a 360-day year and the actual number of days elapsed in each quarterly interest period. The accrued interest for any period will be calculated by multiplying the principal amount of this Security by an accrued interest factor. The accrued interest factor will be computed by summing the daily interest factor applied to each day from the start of the quarterly interest period to the date for which accrued interest is being calculated. The daily interest factor (expressed as a decimal rounded upwards if necessary) will be computed by dividing the interest rate then in effect (expressed as a decimal rounded upwards if necessary) by 360.

The Company will pay the interest payable for any Interest Payment Date to the person in whose name this Security is registered at the close of business (1) on the Business Day prior to each Interest Payment Date if this Security remains in book-entry only form or (2) on the fifteenth calendar day before each Interest Payment Date if this Security does not remain in book-entry only form. Any such interest not so punctually paid or duly provided for will forthwith cease to be payable to the Holder on such date and may either be paid to the person in whose name this Security is registered at the close of business on a Special Record Date for the payment of such Defaulted Interest to be fixed by the Trustee, notice whereof shall be given to Holders of Securities of this series not less than 10 days prior to such Special Record Date, or be paid at any time in any other lawful manner not inconsistent with the requirements of any securities exchange on which the Securities of this series may be listed, and upon such notice as may be required by such exchange, all as more fully provided in said Indenture.

A “Business Day” shall mean any day except a Saturday, a Sunday or a legal holiday in The City of New York or in Pittsburgh, Pennsylvania on which banking institutions are authorized or required by law, regulation or executive order to close; provided, that the day is also a London Business Day. “London Business Day” means any day on which dealings in United States dollars are transacted in the London interbank market.

The calculation agent appointed by the Company with respect to this Security, initially The Bank of New York Mellon Trust Company, N.A. (in such capacity, the “Calculation Agent”), will calculate the interest rate on this Security and, promptly upon such calculation, will notify the Company and the Trustee, if the Trustee is not then serving as the Calculation Agent, of such interest rate. The Calculation Agent will reset the interest rate on each Interest Payment Date, each of which is referred to as an “Interest Reset Date.” The second London Business Day preceding an Interest Reset Date will be the “Interest Determination Date” for that Interest Reset

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Date. The interest rate in effect on each day that is not an Interest Reset Date will be the interest rate determined as of the Interest Determination Date pertaining to the immediately preceding Interest Reset Date. The interest rate in effect on any day that is an Interest Reset Date will be the interest rate determined as of the Interest Determination Date pertaining to that Interest Reset Date, except that the interest rate in effect for the period from and including March 22, 2012 to the first Interest Reset Date will be the initial interest rate. The interest rate on this Security will in no event be higher than the maximum rate permitted by New York law as the same may be modified by United States law of general application.

The Calculation Agent will, upon the request of any Holder, provide the interest rate then in effect. All calculations made by the Calculation Agent in the absence of manifest error shall be conclusive for all purposes and binding on the Company and the Holders. The Company may appoint a successor calculation agent.

All percentages resulting from any calculation of the interest rate with respect to this Security will be rounded, if necessary, to the nearest one-hundred thousandth of a percentage point, with five one-millionths of a percentage point rounded upwards (for example, 9.876545% (or .09876545) being rounded to 9.87655% (or .0987655) and 9.876544% (or .09876544) being rounded to 9.87654% (or .0987654)), and all dollar amounts in or resulting from any such calculation will be rounded to the nearest cent (with one-half cent being rounded upwards).

“LIBOR” means the rate determined by the Calculation Agent in accordance with the following provisions:

(1) With respect to any Interest Determination Date, LIBOR will be the rate for deposits in United States dollars having a maturity of three months commencing on the first day of the applicable interest period that appears on Bloomberg US0003M Page as of 11:00 a.m., London time, on that Interest Determination Date. If no rate appears, then LIBOR, in respect of that Interest Determination Date, will be determined in accordance with the provisions described in (2) below.

(2) With respect to an Interest Determination Date on which no rate appears on Bloomberg US0003M Page, as specified in (1) above, the Calculation Agent will request the principal London offices of each of four major reference banks in the London interbank market, as selected by the Calculation Agent, to provide the Calculation Agent with its offered quotation for deposits in United States dollars for the period of three months, commencing on the first day of the applicable interest period, to prime banks in the London interbank market at approximately 11:00 a.m., London time, on that Interest Determination Date and in a principal amount that is representative for a single transaction in United States dollars in that market at that time. If at least two quotations are provided, then LIBOR on that Interest Determination Date will be the arithmetic mean of those quotations. If fewer than two quotations are provided, then LIBOR on the Interest Determination Date will be the arithmetic mean of the rates quoted at approximately 11:00 a.m., in the City of New York, on the Interest Determination Date by three major banks in the City of New York selected by the Calculation Agent for loans in United States dollars to leading European banks, having a three-month maturity and in a principal amount that is representative for a single transaction in United States dollars in that market at that time; provided, however, that if the banks selected by the Calculation Agent are not providing quotations in the manner described by this sentence, LIBOR will be the same as the rate determined for the immediately preceding Interest Reset Date.

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“Bloomberg US0003M Page” means the display designated on page “US0003M” on Bloomberg (or such other page as may replace the US0003M page on that service or any successor service for the purpose of displaying London interbank offered rates for U.S. dollar deposits of major banks).

Payment of the principal of and any interest on this Security will be made at the office or agency of the Company maintained for that purpose in Pittsburgh, Pennsylvania, in such coin or currency of the United States of America as at the time of payment is legal tender for payment of public and private debts; provided, however, that at the option of the Company payment of interest may be made by check mailed to the address of the Person entitled thereto as such address shall appear in the Security Register.

This Security has initially been issued in the form of a Global Security, and the Company has initially designated The Depository Trust Company, New York, New York (the “Depositary,” which term shall include any successor depositary) as the Depositary for this Security. For as long as this Security or any portion hereof is issued in such form, and notwithstanding the previous paragraph, all payments of interest, principal and other amounts in respect of this Security or portion thereof shall be made to the Depositary or its nominee in accordance with its applicable policies and procedures, in the coin or currency specified above and as further provided on the reverse hereof.

Reference is hereby made to the further provisions of this Security set forth on the reverse hereof, which further provisions shall for all purposes have the same effect as if set forth at this place.

Unless the certificate of authentication hereon has been executed by the Trustee referred to on the reverse hereof by manual signature, this Security shall not be entitled to any benefit under the Indenture or be valid or obligatory for any purpose.

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[Form of Reverse of Global Security]

NORTHEAST UTILITIES

FLOATING RATE SENIOR NOTES, SERIES D, DUE 2013

This Security is one of a duly authorized issue of securities of the Company (herein called the “Securities”), issued and to be issued in one or more series under an Indenture, dated as of April 1, 2002, as amended and supplemented from time to time and as amended and supplemented by the Fourth Supplemental Indenture dated as of March 15, 2012 (herein called the “Indenture”, which term shall have the meaning assigned to it in such instrument), between the Company and The Bank of New York Mellon Trust Company, N.A., formerly known as The Bank of New York Trust Company, N.A. (as successor trustee to The Bank of New York), as Trustee (herein called the “Trustee,” which term includes any successor trustee under Indenture), as to which Indenture and all indentures supplemental thereto reference is hereby made for a statement of the respective rights, limitations of rights, duties and immunities thereunder of the Company, the Trustee and the Holders and of the terms upon which the Securities are, and are to be, authenticated and delivered. This Security is one of the series designated on the face hereof, limited initially in aggregate principal amount to $300,000,000.00. The provisions of this Security, together with the provisions of the Indenture, shall govern the rights, obligations, duties and immunities of the Holder, the Company and the Trustee with respect to this Security, provided that, if any provision of this Security conflicts with any provision of the Indenture, the provision of this Security shall be controlling to the fullest extent permitted under the Indenture.

The Securities of this series will not be subject to any sinking fund and will not be subject to redemption prior to Final Maturity.

If an Event of Default with respect to Securities of this series shall occur and be continuing, the principal of the Securities of this series may be declared due and payable in the manner and with the effect provided in the Indenture.

The Indenture permits, with certain exceptions as therein provided, the amendment thereof and the modification of the rights and obligations of the Company and the rights of the Holders of the Securities of each series to be affected under the Indenture at any time by the Company and the Trustee with the consent of the Holders of a majority in principal amount of the Securities at the time Outstanding of all series to be affected (voting as one class). The Indenture also contains provisions permitting the Holders of specified percentages in principal amount of the Securities of each series at the time Outstanding, on behalf of the Holders of all Securities of such series, to waive compliance by the Company with certain provisions of the Indenture and certain past defaults under the Indenture and their consequences. Any such consent or waiver by the Holder of this Security shall be conclusive and binding upon such Holder and upon all future Holders of this Security and of any Security issued upon the registration of transfer hereof or in exchange herefor or in lieu hereof, whether or not notation of such consent or waiver is made upon this Security.

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No reference herein to the Indenture and no provision of this Security or of the Indenture shall alter or impair the obligation of the Company, which is absolute and unconditional, to pay the principal of (and the premium, if any) and interest, if any, on this Security at the time, place and rate, and in the coin or currency, herein prescribed.

This Security shall be exchangeable for Securities registered in the names of Persons other than the Depositary with respect to such series or its nominee only as provided in this paragraph. This Security shall be so exchangeable if (x) the Depositary notifies the Company that it is unwilling or unable to continue as Depositary for such series or at any time ceases to be a clearing agency registered as such under the Securities Exchange Act of 1934, (y) the Company executes and delivers to the Trustee an Officers’ Certificate providing that this Security shall be so exchangeable or (z) there shall have occurred and be continuing an Event of Default with respect to the Securities of the series of which this Security is a part. Securities so issued in exchange for this Security shall be of the same series, having the same interest rate, if any, and maturity and having the same terms as this Security, in authorized denominations and in the aggregate having the same principal amount as this Security and registered in such names as the Depositary for such Global Security shall direct.

As provided in the Indenture and subject to certain limitations therein set forth, the transfer of a Security of the series of which this Security is a part is registrable in the Security Register, upon surrender of this Security for registration of transfer at the office or agency of the Company in any place where the principal of (and any premium) and interest, if any, on this Security are payable, duly endorsed by, or accompanied by a written instrument of transfer in form satisfactory to the Company and the Security Registrar duly executed by, the Holder hereof or his attorney duly authorized in writing, and thereupon one or more new Securities of this series and of like tenor, of authorized denominations and for the same aggregate principal amount, will be issued to the designated transferee or transferees.

The Securities of the series of which this Security is a part are issuable only in registered form without coupons in denominations of $1,000 and any integral multiple thereof. As provided in the Indenture and subject to certain limitations therein set forth, Securities of this series are exchangeable for a like aggregate principal amount of Securities of this series and of like tenor of a different authorized denomination, as requested by the Holder surrendering the same.

No service charge shall be made for any such registration of transfer or exchange, but the Company may require payment of a sum sufficient to cover any tax or other governmental charge payable in connection therewith.

Prior to due presentment of this Security for registration of transfer, the Company, the Trustee and any agent of the Company or the Trustee may treat the Person in whose name this Security is registered as the owner hereof for all purposes, whether or not this Security be overdue, and neither the Company, the Trustee nor any such agent shall be affected by notice to the contrary.

For so long as this Security is issued in the form of a Global Security, neither the Company nor the Trustee will have any responsibility with respect to the policies and procedures of the Depositary or for any notices or other communications among the Depositary, its direct and indirect participants or the beneficial owners of this Security.

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Neither the failure to give any notice nor any defect in any notice given to the Holder of this Security or any other Security of this series will affect the sufficiency of any notice given to any other Holder of any Securities of this series.

The Indenture provides that the Company, at its option (a) will be discharged from any and all obligations in respect of the Securities (except for certain obligations to register the transfer or exchange of Securities, replace stolen, lost or mutilated Securities, maintain paying agencies and hold moneys for payment in trust) or (b) need not comply with certain restrictive covenants of the Indenture, in each case if the Company deposits, in trust, with the Trustee money or U.S. Government Obligations which, through the payment of interest thereon and principal thereof in accordance with their terms, will provide money, in an amount sufficient to pay all the principal of and premium, if any and interest, if any, on the Securities on the dates such payments are due in accordance with the terms of such Securities, and certain other conditions are satisfied.

No recourse shall be had for the payment of the principal of or the interest on this Security, or for any claim based hereon, or otherwise in respect hereof, or based on or in respect of the Indenture or any indenture supplemental thereto, against any trustee, incorporator, stockholder, officer or director, as such, past, present or future, of the Company or any successor corporation, either directly or through the Company or any successor corporation, whether by virtue of any constitution, statute or rule of law, or by the enforcement of any assessment or penalty or otherwise, all such liability being, by the acceptance hereof and as part of the consideration for the issuance hereof, expressly waived and released.

The Declaration of Trust of the Company provides that no shareholder of the Company shall be held to any liability whatsoever for the payment of any sum of money, or for damages or otherwise under any contract, obligation or undertaking made, entered into or issued by the trustees of the Company or by any officer, agent or representative elected or appointed by the trustees and no such contract, obligation or undertaking shall be enforceable against the trustees or any of them in their or his individual capacities or capacity and all such contracts, obligations and undertakings shall be enforceable only against the trustees as such, and every person, firm, association, trust and corporation having any claim or demand arising out of any such contract, obligation or undertaking shall look only to the trust estate for the payment or satisfaction thereof.

This Security shall be governed by and construed in accordance with the laws of the State of New York.

All terms used in this Security not defined herein which are defined in the Indenture shall have the meanings assigned to them in the Indenture.

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IN WITNESS WHEREOF, Northeast Utilities has caused this instrument to be duly executed.

Dated: March 22, 2012

TRUSTEE’S CERTIFICATE OF AUTHENTICATION

This is one of the Securities of the series designated therein referred to in the within mentioned Indenture.

Dated: March 22, 2012

THE BANK OF NEW YORK MELLON TRUST COMPANY, N.A., as Trustee

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