<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2018-10-19</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001161154</issuerCik>
        <issuerName>Energy Transfer Operating, L.P.</issuerName>
        <issuerTradingSymbol>ETP</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001345700</rptOwnerCik>
            <rptOwnerName>Long Thomas E</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>8111 WESTCHESTER DRIVE, SUITE 600</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>DALLAS</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>75225</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Chief Financial Officer</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Units</value>
            </securityTitle>
            <transactionDate>
                <value>2018-10-19</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>174625</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Disposition in connection with the merger of a wholly owned subsidiary of Energy Transfer Equity, L.P. (&quot;ETE&quot;) with Energy Transfer Partners, L.P. (&quot;ETP&quot;), with ETP continuing as the surviving entity and becoming a wholly owned subsidiary of ETE (the &quot;Merger&quot;). On October 18, 2018, the last trading day for the ETP common units, the closing price of ETP's common units was $21.47 per unit and the closing price of ETE's common units was $16.82 per unit. Each ETP common unit outstanding was converted into the right to receive 1.28 ETE common units.  As part of the Merger, ETE changed its name to &quot;Energy Transfer LP&quot; and its common units began trading on the New York Stock Exchange (&quot;NYSE&quot;) under the &quot;ET&quot; ticker symbol when the market opened on Friday, October 19, 2018.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Peggy J. Harrison, Attorney-in-Fact for Mr. Long</signatureName>
        <signatureDate>2018-10-23</signatureDate>
    </ownerSignature>
</ownershipDocument>
