10-K/A

UNITED STATES SECURITIES AND

EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K/A

Amendment No. 1

x ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the fiscal year ended December 31, 2005

or

¨ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the transition period from                      to                     

Commission file number 1-14768

NSTAR

(Exact name of registrant as specified in its charter)

Massachusetts	04-3466300
(State or other jurisdiction of incorporation or organization)	(I.R.S. Employer Identification Number)
800 Boylston Street, Boston, Massachusetts	02199
(Address of principal executive offices)	(Zip code)

617 424-2000

(Registrant’s telephone number, including area code)

Securities registered pursuant to Section 12(b) of the Act:

Title of each class	Name of each exchange on which registered
Common Shares, Par Value $1 per share	New York Stock Exchange Boston Stock Exchange

Securities registered pursuant to Section 12(g) of the Act: None

Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act.

x  Yes    ¨  No

Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act.

¨  Yes    x  No

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.

x  Yes    ¨  No

Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K is not contained herein, and will not be contained, to the best of registrant’s knowledge, in definitive proxy or information statements incorporated by reference in Part III of this Form 10-K or any amendment to this Form 10-K.  x

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, or a non-accelerated filer, as defined in Rule 12b-2 of the Exchange Act.

Large accelerated filer  x            Accelerated filer  ¨            Non-accelerated filer  ¨

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Act)

¨  Yes    x  No

The aggregate market value of the 106,808,376 shares of voting stock of the registrant held by non-affiliates of the registrant, computed as the average of the high and low market prices of the common shares as reported on the New York Stock Exchange consolidated transaction reporting system for NSTAR Common Shares as of the last business day of the registrant’s most recently completed second fiscal quarter: $3,291,834,148.

Indicate the number of shares outstanding of each of the registrant’s classes of common stock, as of the latest practicable date:

Class	Outstanding at February 17, 2006
Common Shares, $1 par value	106,808,376 Shares

Documents Incorporated by Reference

Sections of NSTAR’s Definitive Proxy Statement for the 2006 Annual Meeting of Shareholders to be held on May 4, 2006 are incorporated by reference into Parts I and III of this Form 10-K.

NSTAR

Form 10-K/A

Amendment No. 1

Table of Contents

	Page
Explanatory Note	2
Item 8. Financial Statements and Supplementary Data
—Consolidated Balance Sheets (replaces page 51 in original filing)	3
Item 15. Exhibits and Financial Statement Schedules	4
Signature	5
Exhibit 31—Rule 13a – 15/15d-15(e) Certifications
Exhibit 32—Section 1350 Certifications

1

Explanatory Note

This Amendment No. 1 to NSTAR’s Annual Report on Form 10-K for the fiscal year ended December 31, 2005 (the “Annual Report”) is being filed solely to amend a single amount on the Consolidated Balance Sheets reflecting the Utility plant in service, at original cost, at December 31, 2005 included in Item 8. As a result of a typographical error by NSTAR’s printer/filing agent made in the process of converting and formatting the Annual Report to an electronic format suitable for filing with the Commission, the EDGAR version of the Form 10-K reflected an incorrect amount for Utility plant in service, at original cost, for 2005 and was filed in the original Form 10-K on February 17, 2006 as $4,454,774 (in thousands). The correct amount should have been $4,671,059 (in thousands). The detailed description of Utility Plant included in the original filing in Note A. “Business Organization and Summary of Significant Accounting Policies,” reflects the correct amount.

Except as described above, no other changes or amendments have been made to the Annual Report as previously filed for changes in events, estimates or other developments subsequent to February 17, 2006, the date of the original filing of the Annual Report. For a discussion of any potential subsequent events and developments that may be material to investors, please refer to the NSTAR’s filings with the Securities and Exchange Commission subsequent to February 17, 2006.

2

Item 8.    Financial Statements and Supplementary Data

NSTAR

Consolidated Balance Sheets

	December 31,
	2005					2004
Assets	(in thousands)
Utility plant in service, at original cost	$	4,671,059				$	4,454,774
Less: accumulated depreciation		1,178,259			3,492,800		1,122,810			3,331,964
Construction work in progress					208,957					103,866
Net utility plant					3,701,757					3,435,830
Non-utility property, net					138,222					144,148
Equity investments					13,705					13,887
Other investments					63,441					59,096
Current assets:
Cash and cash equivalents		15,612					12,497
Restricted cash		14,282					10,254
Accounts receivable, net of allowance of $24,504 and $21,804, respectively		305,441					302,194
Accrued unbilled revenues		59,400					53,752
Regulatory assets		446,286					300,238
Inventory, at average cost		120,924					86,397
Income taxes		57,444					21,063
Other		16,894			1,036,283		11,434			797,829
Deferred debits:
Regulatory assets - energy contracts					683,193					1,269,651
Regulatory asset - goodwill					658,538					678,698
Regulatory assets - other					924,693					607,037
Prepaid pension					346,889					297,746
Other					78,843					87,434
Total assets				$	7,645,564				$	7,391,356
Capitalization and Liabilities
Common equity:
Common shares, par value $1 per share, 200,000,000 shares authorized; 106,808,376 shares in 2005 and 106,550,282 shares in 2004 issued and outstanding	$	106,808				$	106,550
Premium on common shares		813,099					819,454
Retained earnings		621,500					518,252
Accumulated other comprehensive loss		(6,392	)		1,535,015		(3,374	)		1,440,882
Cumulative non-mandatory redeemable preferred stock of subsidiary					43,000					43,000
Long-term debt					1,614,411					1,792,654
Transition property securitization					787,966					308,748
Current liabilities:
Long-term debt		28,457					108,197
Transition property securitization		94,683					41,048
Notes payable		417,500					161,400
Deferred income taxes		7,232					8,072
Accounts payable		320,960					239,613
Energy contracts		183,674					171,312
Accrued interest		33,114					33,073
Dividends payable		327					31,227
Accrued expenses		20,729					30,654
Other		62,769			1,169,445		73,346			897,942
Deferred credits:
Accumulated deferred income taxes and unamortized investment tax credits					1,273,456					1,114,588
Energy contracts					683,193					1,269,651
Pension liability					37,351					31,296
Regulatory liability - cost of removal					258,782					258,722
Other					242,945					233,873
Commitments and contingencies
Total capitalization and liabilities				$	7,645,564				$	7,391,356

The accompanying notes are an integral part of the consolidated financial statements.

3

Item 15. Exhibits and Financial Statement Schedules

NSTAR and its subsidiaries

Exhibit 31	Rule 13a - 15/15d-15(e) Certifications (filed herewith)
31.1	Certification Statement of Chief Executive Officer of NSTAR pursuant to Section 302 of the Sarbanes-Oxley Act of 2002
31.2	Certification Statement of Chief Financial Officer of NSTAR pursuant to Section 302 of the Sarbanes-Oxley Act of 2002
Exhibit 32	Section 1350 Certifications (filed herewith)
32.1	Certification Statement of Chief Executive Officer of NSTAR pursuant to Section 906 of the Sarbanes-Oxley Act of 2002
32.2	Certification Statement of Chief Financial Officer of NSTAR pursuant to Section 906 of the Sarbanes-Oxley Act of 2002

4

FORM 10-K/A NSTAR DECEMBER 31, 2005

SIGNATURE

Pursuant to the requirements of Section 13 or 15(d) 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.

		NSTAR
		(Registrant)
Date: February 27, 2006	By:	/s/    ROBERT J. WEAFER, JR.
		Robert J. Weafer, Jr.
		Vice President, Controller and
		Chief Accounting Officer

5

EX-31.1

Exhibit 31.1

Sarbanes-Oxley Section 302 Certification

I, Thomas J. May, certify that:

1. I have reviewed this annual report on Form 10-K/A of NSTAR;

2. Based on my knowledge, this annual report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this annual report;

3. Based on my knowledge, the financial statements, and other financial information included in this annual report, fairly present in all material respects the financial condition, results of operations and cash flows of NSTAR as of, and for, the periods presented in this annual report;

4. NSTAR’s other certifying officer and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for NSTAR and have:

a) designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to NSTAR, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this annual report is being prepared;

b) designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

c) evaluated the effectiveness of NSTAR’s disclosure controls and procedures and presented in this annual report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this annual report, based on such evaluation; and

d) disclosed in this annual report any change in NSTAR’s internal control over financial reporting that occurred during NSTAR’s most recent fiscal quarter that has materially affected, or is reasonably likely to materially affect, NSTAR’s internal control over financial reporting; and

5. NSTAR’s other certifying officer and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to NSTAR’s auditors and the audit committee of NSTAR’s board of trustees:

a) all significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect NSTAR’s ability to record, process, summarize and report financial information; and

b) any fraud, whether or not material, that involves management or other employees who have a significant role in NSTAR’s internal control over financial reporting.

Date: February 27, 2006	/S/    THOMAS J. MAY
	Thomas J. May Chairman, President and Chief Executive Officer

EX-31.2

Exhibit 31.2

Sarbanes-Oxley Section 302 Certification

I, James J. Judge, certify that:

1. I have reviewed this annual report on Form 10-K/A of NSTAR;

2. Based on my knowledge, this annual report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this annual report;

3. Based on my knowledge, the financial statements, and other financial information included in this annual report, fairly present in all material respects the financial condition, results of operations and cash flows of NSTAR as of, and for, the periods presented in this annual report;

4. NSTAR’s other certifying officer and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for NSTAR and have:

a) designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to NSTAR, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this annual report is being prepared;

b) designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

c) evaluated the effectiveness of NSTAR’s disclosure controls and procedures and presented in this annual report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this annual report, based on such evaluation; and

d) disclosed in this annual report any change in NSTAR’s internal control over financial reporting that occurred during NSTAR’s most recent fiscal quarter that has materially affected, or is reasonably likely to materially affect, NSTAR’s internal control over financial reporting; and

5. NSTAR’s other certifying officer and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to NSTAR’s auditors and the audit committee of NSTAR’s board of trustees:

a) all significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect NSTAR’s ability to record, process, summarize and report financial information; and

b) any fraud, whether or not material, that involves management or other employees who have a significant role in NSTAR’s internal control over financial reporting.

Date: February 27, 2006	/S/    JAMES J. JUDGE
	James J. Judge Senior Vice President, Treasurer and Chief Financial Officer

EX-32.1

Exhibit 32.1

Certification Pursuant To

18 U.S.C. Section 1350,

As Adopted Pursuant To

Section 906 of the Sarbanes-Oxley Act of 2002

The undersigned hereby certifies, in my capacity as an officer of NSTAR, for purposes of 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that to the best of my knowledge:

(i) the enclosed Annual Report of NSTAR on Form 10-K/A for the period ended December 31, 2005 fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

(ii) the information contained in such Annual Report fairly presents, in all material respects, the financial condition and results of operation of NSTAR.

Dated: February 27, 2006

/s/  THOMAS J. MAY            

Thomas J. May

Chairman, President and

Chief Executive Officer

EX-32.2

Exhibit 32.2

Certification Pursuant To

18 U.S.C. Section 1350,

As Adopted Pursuant To

Section 906 of the Sarbanes-Oxley Act of 2002

The undersigned hereby certifies, in my capacity as an officer of NSTAR, for purposes of 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that to the best of my knowledge:

(i) the enclosed Annual Report of NSTAR on Form 10-K/A for the period ended December 31, 2005 fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

(ii) the information contained in such Annual Report fairly presents, in all material respects, the financial condition and results of operation of NSTAR.

Dated: February 27, 2006

/s/  JAMES J. JUDGE            

James J. Judge

Senior Vice President, Treasurer

and Chief Financial Officer