credit facilities as our bermuda subsidiaries are not admitted insurers and reinsurers in the u.s. , the terms of certain u.s . insurance and reinsurance contracts require them to provide collateral , which can be in the form of locs . in addition , ace global markets is required to satisfy certain u.s . regulatory trust fund requirements which can be met by the issuance of locs . locs may also be used for general corporate purposes and to provide underwriting capacity as funds at lloyd 2019s . the following table shows our main credit facilities by credit line , usage , and expiry date at december 31 , 2010 . ( in millions of u.s . dollars ) credit line ( 1 ) usage expiry date .
what is the total credit line utilization rate?
( 1 ) certain facilities are guaranteed by operating subsidiaries and/or ace limited . ( 2 ) may also be used for locs . ( 3 ) supports ace global markets underwriting capacity for lloyd 2019s syndicate 2488 ( see discussion below ) . in november 2010 , we entered into four letter of credit facility agreements which collectively permit the issuance of up to $ 400 million of letters of credit . we expect that most of the locs issued under the loc agreements will be used to support the ongoing funds at lloyd 2019s requirements of syndicate 2488 , but locs may also be used for other general corporate purposes . it is anticipated that our commercial facilities will be renewed on expiry but such renewals are subject to the availability of credit from banks utilized by ace . in the event that such credit support is insufficient , we could be required to provide alter- native security to clients . this could take the form of additional insurance trusts supported by our investment portfolio or funds withheld using our cash resources . the value of letters of credit required is driven by , among other things , statutory liabilities reported by variable annuity guarantee reinsurance clients , loss development of existing reserves , the payment pattern of such reserves , the expansion of business , and loss experience of such business . the facilities in the table above require that we maintain certain covenants , all of which have been met at december 31 , 2010 . these covenants include : ( i ) maintenance of a minimum consolidated net worth in an amount not less than the 201cminimum amount 201d . for the purpose of this calculation , the minimum amount is an amount equal to the sum of the base amount ( currently $ 13.8 billion ) plus 25 percent of consolidated net income for each fiscal quarter , ending after the date on which the current base amount became effective , plus 50 percent of any increase in consolidated net worth during the same period , attributable to the issuance of common and preferred shares . the minimum amount is subject to an annual reset provision . ( ii ) maintenance of a maximum debt to total capitalization ratio of not greater than 0.35 to 1 . under this covenant , debt does not include trust preferred securities or mezzanine equity , except where the ratio of the sum of trust preferred securities and mezzanine equity to total capitalization is greater than 15 percent . in this circumstance , the amount greater than 15 percent would be included in the debt to total capitalization ratio . at december 31 , 2010 , ( a ) the minimum consolidated net worth requirement under the covenant described in ( i ) above was $ 14.5 billion and our actual consolidated net worth as calculated under that covenant was $ 21.6 billion and ( b ) our ratio of debt to total capitalization was 0.167 to 1 , which is below the maximum debt to total capitalization ratio of 0.35 to 1 as described in ( ii ) above . our failure to comply with the covenants under any credit facility would , subject to grace periods in the case of certain covenants , result in an event of default . this could require us to repay any outstanding borrowings or to cash collateralize locs under such facility . a failure by ace limited ( or any of its subsidiaries ) to pay an obligation due for an amount exceeding $ 50 million would result in an event of default under all of the facilities described above . ratings ace limited and its subsidiaries are assigned debt and financial strength ( insurance ) ratings from internationally recognized rating agencies , including s&p , a.m . best , moody 2019s investors service , and fitch . the ratings issued on our companies by these agencies are announced publicly and are available directly from the agencies . our internet site , www.acegroup.com .