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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2016-01-04</periodOfReport>

    <issuer>
        <issuerCik>0000783325</issuerCik>
        <issuerName>WEC ENERGY GROUP, INC.</issuerName>
        <issuerTradingSymbol>WEC</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001241250</rptOwnerCik>
            <rptOwnerName>STANEK MARY ELLEN</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>231 W MICHIGAN STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>MILWAUKEE</rptOwnerCity>
            <rptOwnerState>WI</rptOwnerState>
            <rptOwnerZipCode>53203</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2016-01-04</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>2371.4983</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>6912.5077</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2016-01-04</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>2455</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>9367.5077</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Phantom Stock Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F3"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2016-01-04</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>2371.4983</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F4"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F4"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>2371.4983</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>8044.799</value>
                    <footnoteId id="F5"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Upon the vesting of restricted stock granted to the reporting person on January 2, 2013, the reporting person deferred the receipt of 2,371.4983 shares of common stock and instead received 2,371.4983 phantom stock units pursuant to the DDCP. As a result, the reporting person is reporting the disposition of 2,371.4983 shares of common stock in exchange for an equal number of phantom stock units.</footnote>
        <footnote id="F2">Includes shares acquired pursuant to dividend reinvestment in transactions exempt from Section 16 pursuant to Rule 16a-11.</footnote>
        <footnote id="F3">One-for-one.</footnote>
        <footnote id="F4">These phantom stock units were accrued under the WEC Energy Group, Inc. Directors' Deferred Compensation Plan (DDCP) and are to be settled following the reporting person's termination of service as a director.</footnote>
        <footnote id="F5">Includes phantom stock units accrued pursuant to a dividend reinvesment feature of the DDCP in transactions exempt from Section 16 pursuant to Rule 16a-11.</footnote>
    </footnotes>

    <remarks>Exhibit List: Exhibit 24 - Power of Attorney</remarks>

    <ownerSignature>
        <signatureName>/s/ Joshua M. Erickson, as Attorney-in-Fact</signatureName>
        <signatureDate>2016-01-06</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0306
4
2016-01-04
0000783325
WEC ENERGY GROUP, INC.
WEC
0001241250
STANEK MARY ELLEN
231 W MICHIGAN STREET
MILWAUKEE
WI
53203
1
0
0
0
Common Stock
2016-01-04
4
D
0
2371.4983
D
6912.5077
D
Common Stock
2016-01-04
4
A
0
2455
0
A
9367.5077
D
Phantom Stock Units
2016-01-04
4
A
0
2371.4983
0
A
Common Stock
2371.4983
8044.799
D
Upon the vesting of restricted stock granted to the reporting person on January 2, 2013, the reporting person deferred the receipt of 2,371.4983 shares of common stock and instead received 2,371.4983 phantom stock units pursuant to the DDCP. As a result, the reporting person is reporting the disposition of 2,371.4983 shares of common stock in exchange for an equal number of phantom stock units.
Includes shares acquired pursuant to dividend reinvestment in transactions exempt from Section 16 pursuant to Rule 16a-11.
One-for-one.
These phantom stock units were accrued under the WEC Energy Group, Inc. Directors' Deferred Compensation Plan (DDCP) and are to be settled following the reporting person's termination of service as a director.
Includes phantom stock units accrued pursuant to a dividend reinvesment feature of the DDCP in transactions exempt from Section 16 pursuant to Rule 16a-11.
Exhibit List: Exhibit 24 - Power of Attorney
/s/ Joshua M. Erickson, as Attorney-in-Fact
2016-01-06