Filed by Northeast Utilities Pursuant to Rule 425

Under the Securities Act of 1933

And Deemed Filed Pursuant to Rule 14a-6

Under the Securities Exchange Act of 1934

Subject Company: NSTAR

Commission File No.: 333-170754

NU-NSTAR merger vote

Proxy materials for the Special Meeting of NU Shareholders to approve the proposed NU-NSTAR merger, scheduled for March 4, 2011, were first sent to NU shareholders on January 5, 2011. Employees and retirees who previously elected to obtain proxy materials electronically using the Internet should have received an e-mail from eproxy@mobular.com during the week of January 10 informing them of their control number and asking them to vote their NU common shares online. NU shareholders, including employees and retirees, who did not elect electronic delivery will receive their joint proxy statement/prospectus and proxy card for the Special Meeting through the mail. Employees may receive more than one set of proxy materials if they own NU common shares through our 401K Plan and through another plan, such as the Employee Share Purchase Plan. Please vote all proxies you receive.

Your vote is very important as approval of the merger proposal requires the affirmative vote of the holders of at least two-thirds of the outstanding NU common shares entitled to vote. Please remember to vote, and if you have questions concerning the proposed NU-NSTAR merger, please contact your Investor Relations group at (860) 728-4652 or (860) 728-4650.

Information Concerning Forward-Looking Statements

In addition to historical information, this communication may contain a number of “forward-looking statements” as defined in the Private Securities Litigation Reform Act of 1995. Words such as anticipate, expect, project, intend, plan, believe, and words and terms of similar substance used in connection with any discussion of future plans, actions, or events identify forward-looking statements. Forward-looking statements relating to the proposed merger include, but are not limited to: statements about the benefits of the proposed merger involving NSTAR and Northeast Utilities, including future financial and operating results; NSTAR’s and Northeast Utilities’ plans, objectives, expectations and intentions; the expected timing of completion of the transaction; and other statements relating to the merger that are not historical facts. Forward-looking statements involve estimates, expectations and projections and, as a result, are subject to risks and uncertainties. There can be no assurance that actual results will not materially differ from expectations. Important factors could cause actual results to differ materially from those indicated by such forward-looking statements. With respect to the proposed merger, these factors include, but are not limited to: risks and uncertainties relating to the ability to obtain the requisite NSTAR and Northeast Utilities shareholder approvals; the risk that NSTAR or Northeast Utilities may be unable to obtain governmental and regulatory approvals required for the merger, or required governmental and regulatory approvals may delay the merger or result in the imposition of conditions that could reduce the anticipated benefits from the merger or cause the parties to abandon the merger; the risk that a condition to closing of the merger may not be satisfied; the length of time necessary to consummate the proposed merger; the risk that the businesses will not be integrated successfully; the risk that the cost savings and any other synergies from the transaction may not be fully realized or may take longer to realize than expected; disruption from the transaction making it more difficult to maintain relationships with customers, employees or suppliers; the diversion of management time on merger-related issues; the effect of future regulatory or legislative actions on the companies; and the risk that the credit ratings of the combined company or its subsidiaries may be different from what the companies expect. These risks, as well as other risks associated with the merger, are more fully discussed in the joint proxy statement/prospectus that is included in the Registration Statement on Form S-4 (Registration No. 333-170754) that was filed by Northeast Utilities with the SEC in connection with the merger. Additional risks and uncertainties are identified and discussed in NSTAR’s and Northeast Utilities’ reports filed with the SEC and available at the SEC’s website at www.sec.gov. Forward-looking statements included in this document speak only as of the date of this document. Neither NSTAR nor Northeast Utilities undertakes any obligation to update its forward-looking statements to reflect events or circumstances after the date of this document.

Additional Information and Where To Find It

This communication does not constitute an offer to sell or the solicitation of an offer to buy any securities or a solicitation of any vote or approval. In connection with the proposed merger between Northeast Utilities and NSTAR, Northeast Utilities filed with the SEC a Registration Statement on Form S-4 (Registration No. 333-170754) that includes a joint proxy statement of Northeast Utilities and NSTAR that also constitutes a prospectus of Northeast Utilities. Northeast Utilities and NSTAR mailed the definitive joint proxy statement/prospectus to their respective shareholders, on or about January 5, 2011. Northeast Utilities and NSTAR urge investors and shareholders to read the joint proxy statement/prospectus regarding the proposed merger, as well as other documents filed with the SEC, because they contain important information. You may obtain copies of all documents filed with the SEC regarding this proposed transaction, free of charge, at the SEC’s website (www.sec.gov). You may also obtain these documents, free of charge, from Northeast Utilities’ website (www.nu.com) under the tab “Investors” and then under the heading “Financial/SEC Reports.” You may also obtain these documents, free of charge, from NSTAR’s website (www.nstar.com) under the tab “Investor Relations.”