I am using the NPV() function in VB.NET to get NPV for a set of cash flows.
However, the result of NPV() is not consistent with my results performing the calculation manually (nor the Investopedia NPV calc... which matches my manual results)
My correct manual results and the NPV() results are close, within 5%.. but not the same...
Manually, using the NPV formula:
NPV = C0 + C1/(1+r)^1 + C2/(1+r)^2 + C3/(1+r)^3 + .... + Cn/(1+r)^n
The manual result is stored in RunningTotal
With rate r = 0.04
and period n = 10
Here is my relevant code:
EDIT: Do I have OBOB somewhere?
YearCashOutFlow = CDbl(TxtAnnualCashOut.Text)
YearCashInFlow = CDbl(TxtTotalCostSave.Text)
YearCount = 1
PAmount = -1 * (CDbl(TxtPartsCost.Text) + CDbl(TxtInstallCost.Text))
RunningTotal = PAmount
YearNPValue = PAmount
AnnualRateIncrease = CDbl(TxtUtilRateInc.Text)
While AnnualRateIncrease > 1
AnnualRateIncrease = AnnualRateIncrease / 100
End While
AnnualRateIncrease = 1 + AnnualRateIncrease
' ZERO YEAR ENTRIES
ListBoxNPV.Items.Add(Format(PAmount, "currency"))
ListBoxCostSave.Items.Add("$0.00")
ListBoxIRR.Items.Add("-100")
ListBoxNPVCum.Items.Add(Format(PAmount, "currency"))
CashFlows(0) = PAmount
''''
Do While YearCount <= CInt(TxtLifeOfProject.Text)
ReDim Preserve CashFlows(YearCount)
CashFlows(YearCount) = Math.Round(YearCashInFlow - YearCashOutFlow, 2)
If CashFlows(YearCount) > 0 Then OnePos = True
YearNPValue = CashFlows(YearCount) / (1 + DiscountRate) ^ YearCount
RunningTotal = RunningTotal + YearNPValue
ListBoxNPVCum.Items.Add(Format(Math.Round(RunningTotal, 2), "currency"))
ListBoxCostSave.Items.Add(Format(YearCashInFlow, "currency"))
If OnePos Then
ListBoxIRR.Items.Add((IRR(CashFlows, 0.1)).ToString)
ListBoxNPV.Items.Add(Format(NPV(DiscountRate, CashFlows), "currency"))
Else
ListBoxIRR.Items.Add("-100")
ListBoxNPV.Items.Add(Format(RunningTotal, "currency"))
End If
YearCount = YearCount + 1
YearCashInFlow = AnnualRateIncrease * YearCashInFlow
Loop
