Exhibit
10.4


 


Execution
Version


 


TortoiseEcofin
Acquisition Corp. III


6363
College Boulevard


Overland
Park, KS 66211


 


July
19, 2021


 


Tortoise
Capital Advisors, L.L.C.


6363
College Boulevard


Overland
Park, KS 66211


 


		Re:	Administrative
                                            Support Agreement



 


Ladies
and Gentlemen:


 


This
letter agreement by and between TortoiseEcofin Acquisition Corp. III (the “Company”) and Tortoise Capital Advisors,
L.L.C. (“Tortoise Capital Advisors”), dated as of the date hereof, will confirm our agreement that, commencing
on the date the securities of the Company are first listed on the New York Stock Exchange (the “Listing Date”),
pursuant to a Registration Statement on Form S-1 and prospectus filed with the U.S. Securities and Exchange Commission (the “Registration
Statement”) and continuing until the earlier of the consummation by the Company of an initial business combination and
the Company’s liquidation (in each case as described in the Registration Statement) (such earlier date hereinafter referred to
as the “Termination Date”):


 


(i)
Tortoise Capital Advisors shall make available (or cause other persons to make available) to the Company, at 6363 College Boulevard,
Overland Park, KS 66211 (or any successor location of Tortoise Capital Advisors), certain office space, utilities and secretarial and
administrative support as may be reasonably required by the Company. As reimbursement therefor, the Company shall pay Tortoise Capital
Advisors (and Tortoise Capital Advisors will receive on behalf of itself or, to the extent it causes another person to make support available
to the Company, as nominee on behalf of such other person) the sum of $10,000 per month beginning on the Listing Date and continuing
monthly thereafter until the Termination Date; provided, however, if the Listing Date occurs on a day other than the first
day of the month, the first payment due under this letter agreement shall be pro-rated based on a 30 day month. Although the sums payable
hereunder are fixed, the parties intend that such sums constitute solely a reimbursement for the costs described herein without any mark-up
or other profits and agree that such fixed sums constitute a reasonable estimate of such costs.


 


(ii)
Tortoise Capital Advisors hereby irrevocably waives any and all right, title, interest, causes of action and claims of any kind as a
result of, or arising out of, this letter agreement (each, a “Claim”) in or to, and any and all right to seek
payment of any amounts due to it out of, the trust account established for the benefit of the public shareholders of the Company and
into which substantially all of the proceeds of the Company’s initial public offering will be deposited (the “Trust
Account”), and hereby irrevocably waives any Claim it may have in the future, which Claim would reduce, encumber or otherwise
adversely affect the Trust Account or any monies or other assets in the Trust Account, and further agrees not to seek recourse, reimbursement,
payment or satisfaction of any Claim against the Trust Account or any monies or other assets in the Trust Account for any reason whatsoever.


 


This
letter agreement constitutes the entire agreement and understanding of the parties hereto in respect of its subject matter and supersedes
all prior understandings, agreements or representations by or among the parties hereto, written or oral, to the extent they relate in
any way to the subject matter hereof or the transactions contemplated hereby.


 


This
letter agreement may not be amended, modified or waived as to any particular provision, except by a written instrument executed by the
parties hereto.


 


No
party hereto may assign either this letter agreement or any of its rights, interests or obligations hereunder without the prior written
approval of the other party; provided, however, that Tortoise Capital Advisors may assign this letter agreement, in whole
or in part, to any other person that it directly, or indirectly through one or more intermediaries, controls, or is controlled by, or
is under common control with, without the prior written approval of the Company. Any purported assignment in violation of this paragraph
shall be void and ineffectual and shall not operate to transfer or assign any interest or title to the purported assignee.


 


This
letter agreement constitutes the entire relationship of the parties hereto, and any litigation between the parties (whether grounded
in contract, tort, statute, law or equity) shall be governed by, construed in accordance with, and interpreted pursuant to the laws of
the State of New York, without giving effect to its choice of laws principles.


 


[signature
page follows]


 




    	 



     


    

 


	 	Very
    truly yours,
	 	 	 	 
	 	TortoiseEcofin
    Acquisition Corp. III
	 	 	 	 
	 	By:	/s/
    Vincent T. Cubbage 
	 	 	Name:	Vincent
    T. Cubbage
	 	 	Title:	Chief
    Executive Officer 





 


	AGREED
    TO AND ACCEPTED BY:	 
	 	 
	TORTOISE
    CAPITAL ADVISORS, L.L.C.	 
	 	 	 	 
	By:	/s/
    Michelle Johnston 	 
	 	Name:	Michelle
    Johnston	 
	 	Title:	Authorized
    Signer	 


 


[Signature
Page to Administrative Support Agreement]