Exhibit 32

CERTIFICATIONS OF CEO AND CFO PURSUANT TO
18 U.S.C. SECTION 1350,
AS ADOPTED PURSUANT TO
SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

In connection with this Annual Report on Form 10-K of the Ridgewood
Energy U Fund, LLC (the Fund) for the fiscal year ended December 31, 2007, as
filed with the Securities and Exchange Commission on the date hereof, (the
Report), each of the undersigned officers of the Fund hereby certifies,
pursuant to 18 U.S.C. (section) 1350, as adopted pursuant to (section) 906 of
the Sarbanes-Oxley Act of 2002, that to the best of their knowledge:

| |     |                                                                                                                                                    
| | --- | ---------------------------------------------------------------------------------------------------------------------------------------------------
| | (1) | The Report fully complies with the requirements of Section 13(a) or
 15(d) of the Securities Exchange Act of 1934; and                             
| |     |                                                                                                                                                    
| | (2) | The information contained in the Report fairly presents, in all
 material respects, the financial condition and results of operations of the
 Fund.

|                          |  |     |        |                               |                                                      
|------------------------- |  | --- | ------ | ----------------------------- | -----------------------------------------------------
|Dated: February 20,
 2008 |  |     |        | RIDGEWOOD
 ENERGY U FUND, LLC
|                         
|                          |  | By: | /s/    |                               | ROBERT E.
 SWANSON                                   
|                          |  |     | Name:  |                               | Robert E.
 Swanson                                   
|                          |  |     | Title: |                               | President
 and Chief Executive Officer               
|                          |  |     |        |                               | (Principal
 Executive Officer)                       
|                         
|                          |  |     |        |                               |                                                      
|Dated: February 20,
 2008 |  |     |        |                              
|                          |  | By: | /s/    |                               | KATHLEEN P.
 MCSHERRY                                
|                          |  |     | Name:  |                               | Kathleen P.
 McSherry                                
|                          |  |     | Title: |                               | Executive
 Vice President and Chief Financial Officer
|                          |  |     |        |                               | (Principal
 Financial and Accounting Officer)        

A signed
original of this written statement or other document authenticating,
acknowledging, or otherwise adopting the signature that appears in typed form
within the electronic version of this written statement has been provided to Ridgewood
Energy U Fund, LLC and will be retained by Ridgewood Energy U Fund, LLC and
furnished to the Securities and Exchange Commission or its staff upon request.
The foregoing certification is being furnished solely pursuant to 18 U.S.C.
Section 1350 and is not being filed as part of this report or as a separate
disclosure document.

---