<?xml version="1.0" encoding="us-ascii"?><InstanceReport xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"><Version>2.4.0.8</Version><ReportLongName>00000009 - Disclosure - DEFERRED FINANCING COSTS</ReportLongName><DisplayLabelColumn>true</DisplayLabelColumn><ShowElementNames>false</ShowElementNames><RoundingOption /><HasEmbeddedReports>false</HasEmbeddedReports><Columns><Column FlagID="0"><Id>1</Id><IsAbstractGroupTitle>false</IsAbstractGroupTitle><LabelSeparator>

</LabelSeparator><CurrencyCode /><FootnoteIndexer /><hasSegments>false</hasSegments><hasScenarios>false</hasScenarios><MCU><KeyName /><CurrencySymbol /><contextRef><ContextID>From2013-03-01to2013-05-31</ContextID><EntitySchema>http://www.sec.gov/CIK</EntitySchema><EntityValue>0001084597</EntityValue><PeriodDisplayName /><PeriodType>duration</PeriodType><PeriodStartDate>2013-03-01T00:00:00</PeriodStartDate><PeriodEndDate>2013-05-31T00:00:00</PeriodEndDate><Segments /><Scenarios /></contextRef><UPS /><CurrencyCode /><OriginalCurrencyCode /></MCU><CurrencySymbol /><Labels><Label Key="CalendarSupplement" Id="0" Label="3 Months Ended" /><Label Key="Calendar" Id="1" Label="May 31, 2013" /></Labels></Column></Columns><Rows><Row FlagID="0"><Id>1</Id><IsAbstractGroupTitle>true</IsAbstractGroupTitle><LabelSeparator>

</LabelSeparator><Level>1</Level><ElementName>XPWR_NotesToFinancialStatementsAbstract</ElementName><ElementPrefix>XPWR_</ElementPrefix><IsBaseElement>false</IsBaseElement><BalanceType>na</BalanceType><PeriodType>duration</PeriodType><IsReportTitle>false</IsReportTitle><IsSegmentTitle>false</IsSegmentTitle><IsCalendarTitle>false</IsCalendarTitle><IsEquityPrevioslyReportedAsRow>false</IsEquityPrevioslyReportedAsRow><IsEquityAdjustmentRow>false</IsEquityAdjustmentRow><IsBeginningBalance>false</IsBeginningBalance><IsEndingBalance>false</IsEndingBalance><IsReverseSign>false</IsReverseSign><FootnoteIndexer /><Cells><Cell FlagID="0" ContextID="" UnitID=""><Id>1</Id><IsNumeric>false</IsNumeric><IsRatio>false</IsRatio><DisplayZeroAsNone>false</DisplayZeroAsNone><NumericAmount>0</NumericAmount><RoundedNumericAmount>0</RoundedNumericAmount><NonNumbericText /><FootnoteIndexer /><CurrencyCode /><CurrencySymbol /><IsIndependantCurrency>false</IsIndependantCurrency><ShowCurrencySymbol>false</ShowCurrencySymbol><DisplayDateInUSFormat>false</DisplayDateInUSFormat></Cell></Cells><ElementDataType>xbrli:stringItemType</ElementDataType><SimpleDataType>string</SimpleDataType><IsTotalLabel>false</IsTotalLabel><UnitID>0</UnitID><Label>Notes to Financial Statements</Label></Row><Row FlagID="0"><Id>2</Id><IsAbstractGroupTitle>false</IsAbstractGroupTitle><LabelSeparator>

</LabelSeparator><Level>2</Level><ElementName>XPWR_DeferredFinancingCostsTextBlock</ElementName><ElementPrefix>XPWR_</ElementPrefix><IsBaseElement>false</IsBaseElement><BalanceType>na</BalanceType><PeriodType>duration</PeriodType><IsReportTitle>false</IsReportTitle><IsSegmentTitle>false</IsSegmentTitle><IsCalendarTitle>false</IsCalendarTitle><IsEquityPrevioslyReportedAsRow>false</IsEquityPrevioslyReportedAsRow><IsEquityAdjustmentRow>false</IsEquityAdjustmentRow><IsBeginningBalance>false</IsBeginningBalance><IsEndingBalance>false</IsEndingBalance><IsReverseSign>false</IsReverseSign><FootnoteIndexer /><Cells><Cell FlagID="0" ContextID="From2013-03-01to2013-05-31" UnitID=""><Id>1</Id><IsNumeric>false</IsNumeric><IsRatio>false</IsRatio><DisplayZeroAsNone>false</DisplayZeroAsNone><NumericAmount>0</NumericAmount><RoundedNumericAmount>0</RoundedNumericAmount><NonNumbericText>&lt;p style="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify"&gt;&lt;font style="font: 10pt Times New Roman, Times, Serif"&gt;We
defer certain costs associated with financing activities related to the issuance of equity securities (deferred offering costs)
and debt securities (deferred financing costs). These costs consist primarily of legal, banking and other professional fees related
to the transactions. Upon successful completion of the offering of equity securities, deferred offering costs are recorded as
a reduction of the net proceeds in paid in capital. If the offering is not successful, such costs will be expensed. Deferred financing
costs are amortized over the life of the related debt.&lt;/font&gt;&lt;/p&gt;

&lt;p style="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify"&gt;&lt;font style="font: 10pt Times New Roman, Times, Serif"&gt;&amp;#160;&lt;/font&gt;&lt;/p&gt;

&lt;p style="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify"&gt;&lt;font style="font: 10pt Times New Roman, Times, Serif"&gt;Deferred
financing costs consisted of the following:&lt;/font&gt;&lt;/p&gt;

&lt;p style="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify"&gt;&lt;font style="font: 10pt Times New Roman, Times, Serif"&gt;&amp;#160;&lt;/font&gt;&lt;/p&gt;

&lt;table cellspacing="0" cellpadding="0" align="center" style="width: 50%; border-collapse: collapse; font-size: 10pt"&gt;
&lt;tr style="vertical-align: bottom"&gt;
    &lt;td&gt;&lt;font style="font: 10pt Times New Roman, Times, Serif"&gt;&amp;#160;&lt;/font&gt;&lt;/td&gt;
    &lt;td colspan="3" style="border-bottom: black 1pt solid; text-align: center"&gt;&lt;font style="font: 10pt Times New Roman, Times, Serif"&gt;May
    31 , 2013&lt;/font&gt;&lt;/td&gt;
    &lt;td style="padding-bottom: 1pt"&gt;&lt;font style="font: 10pt Times New Roman, Times, Serif"&gt;&amp;#160;&lt;/font&gt;&lt;/td&gt;
    &lt;td colspan="3" style="border-bottom: black 1pt solid; text-align: center"&gt;&lt;font style="font: 10pt Times New Roman, Times, Serif"&gt;February
    28, 2013&lt;/font&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr style="background-color: rgb(204,238,204); vertical-align: bottom"&gt;
    &lt;td style="text-align: left; padding-left: 5.4pt; width: 55%"&gt;&lt;font style="font: 10pt Times New Roman, Times, Serif"&gt;Deferred
    financing costs&lt;/font&gt;&lt;/td&gt;
    &lt;td style="text-align: left; width: 1%"&gt;&lt;font style="font: 10pt Times New Roman, Times, Serif"&gt;$&lt;/font&gt;&lt;/td&gt;
    &lt;td style="text-align: right; width: 20%"&gt;&lt;font style="font: 10pt Times New Roman, Times, Serif"&gt;85,204&lt;/font&gt;&lt;/td&gt;
    &lt;td style="text-align: left; width: 1%"&gt;&lt;font style="font: 10pt Times New Roman, Times, Serif"&gt;&amp;#160;&lt;/font&gt;&lt;/td&gt;
    &lt;td style="width: 1%"&gt;&lt;font style="font: 10pt Times New Roman, Times, Serif"&gt;&amp;#160;&lt;/font&gt;&lt;/td&gt;
    &lt;td style="text-align: left; width: 1%"&gt;&lt;font style="font: 10pt Times New Roman, Times, Serif"&gt;$&lt;/font&gt;&lt;/td&gt;
    &lt;td style="text-align: right; width: 20%"&gt;&lt;font style="font: 10pt Times New Roman, Times, Serif"&gt;85,204&lt;/font&gt;&lt;/td&gt;
    &lt;td style="text-align: left; width: 1%"&gt;&lt;font style="font: 10pt Times New Roman, Times, Serif"&gt;&amp;#160;&lt;/font&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr style="background-color: white; vertical-align: bottom"&gt;
    &lt;td style="text-align: left; padding-bottom: 1pt; padding-left: 5.4pt"&gt;&lt;font style="font: 10pt Times New Roman, Times, Serif"&gt;Less:
    accumulated amortization&lt;/font&gt;&lt;/td&gt;
    &lt;td style="border-bottom: black 1pt solid; text-align: left"&gt;&lt;font style="font: 10pt Times New Roman, Times, Serif"&gt;&amp;#160;&lt;/font&gt;&lt;/td&gt;
    &lt;td style="border-bottom: black 1pt solid; text-align: right"&gt;&lt;font style="font: 10pt Times New Roman, Times, Serif"&gt;(56,759&lt;/font&gt;&lt;/td&gt;
    &lt;td style="text-align: left; padding-bottom: 1pt"&gt;&lt;font style="font: 10pt Times New Roman, Times, Serif"&gt;)&lt;/font&gt;&lt;/td&gt;
    &lt;td style="padding-bottom: 1pt"&gt;&lt;font style="font: 10pt Times New Roman, Times, Serif"&gt;&amp;#160;&lt;/font&gt;&lt;/td&gt;
    &lt;td style="border-bottom: black 1pt solid; text-align: left"&gt;&lt;font style="font: 10pt Times New Roman, Times, Serif"&gt;&amp;#160;&lt;/font&gt;&lt;/td&gt;
    &lt;td style="border-bottom: black 1pt solid; text-align: right"&gt;&lt;font style="font: 10pt Times New Roman, Times, Serif"&gt;(33,791&lt;/font&gt;&lt;/td&gt;
    &lt;td style="text-align: left; padding-bottom: 1pt"&gt;&lt;font style="font: 10pt Times New Roman, Times, Serif"&gt;)&lt;/font&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;tr style="background-color: rgb(204,238,204); vertical-align: bottom"&gt;
    &lt;td style="text-align: left; padding-bottom: 2.5pt; padding-left: 5.4pt"&gt;&lt;font style="font: 10pt Times New Roman, Times, Serif"&gt;Deferred
    financing costs, net&lt;/font&gt;&lt;/td&gt;
    &lt;td style="border-bottom: black 2.5pt double; text-align: left"&gt;&lt;font style="font: 10pt Times New Roman, Times, Serif"&gt;$&lt;/font&gt;&lt;/td&gt;
    &lt;td style="border-bottom: black 2.5pt double; text-align: right"&gt;&lt;font style="font: 10pt Times New Roman, Times, Serif"&gt;28,445&lt;/font&gt;&lt;/td&gt;
    &lt;td style="text-align: left; padding-bottom: 2.5pt"&gt;&lt;font style="font: 10pt Times New Roman, Times, Serif"&gt;&amp;#160;&lt;/font&gt;&lt;/td&gt;
    &lt;td style="padding-bottom: 2.5pt"&gt;&lt;font style="font: 10pt Times New Roman, Times, Serif"&gt;&amp;#160;&lt;/font&gt;&lt;/td&gt;
    &lt;td style="border-bottom: black 2.5pt double; text-align: left"&gt;&lt;font style="font: 10pt Times New Roman, Times, Serif"&gt;$&lt;/font&gt;&lt;/td&gt;
    &lt;td style="border-bottom: black 2.5pt double; text-align: right"&gt;&lt;font style="font: 10pt Times New Roman, Times, Serif"&gt;51,413&lt;/font&gt;&lt;/td&gt;
    &lt;td style="text-align: left; padding-bottom: 2.5pt"&gt;&lt;font style="font: 10pt Times New Roman, Times, Serif"&gt;&amp;#160;&lt;/font&gt;&lt;/td&gt;&lt;/tr&gt;
&lt;/table&gt;</NonNumbericText><FootnoteIndexer /><CurrencyCode /><CurrencySymbol /><IsIndependantCurrency>false</IsIndependantCurrency><ShowCurrencySymbol>false</ShowCurrencySymbol><DisplayDateInUSFormat>false</DisplayDateInUSFormat></Cell></Cells><ElementDataType>nonnum:textBlockItemType</ElementDataType><SimpleDataType>na</SimpleDataType><ElementDefenition>No authoritative reference available.</ElementDefenition><ElementReferences>No definition available.</ElementReferences><IsTotalLabel>false</IsTotalLabel><UnitID>0</UnitID><Label>DEFERRED FINANCING COSTS</Label></Row></Rows><Footnotes /><IsEquityReport>false</IsEquityReport><ReportName>DEFERRED FINANCING COSTS</ReportName><MonetaryRoundingLevel>UnKnown</MonetaryRoundingLevel><SharesRoundingLevel>UnKnown</SharesRoundingLevel><PerShareRoundingLevel>UnKnown</PerShareRoundingLevel><ExchangeRateRoundingLevel>UnKnown</ExchangeRateRoundingLevel><HasCustomUnits>true</HasCustomUnits><IsEmbedReport>false</IsEmbedReport><IsMultiCurrency>false</IsMultiCurrency><ReportType>Sheet</ReportType><RoleURI>http://XPWR/role/DeferredFinancingCosts</RoleURI><NumberOfCols>1</NumberOfCols><NumberOfRows>2</NumberOfRows></InstanceReport>
