Ventana software support forum

dear forum,
i intend to calculate investment model (to find out investment period and NPV) and I made a submodel like the attached one. But surprisingly the result was different from manual calculation using Excel.
Can anybody help telling me what went wrong with my model?
Thanks and regards

It's impossible to help with just screen shots.

Have you reviewed the documentation for the NPV/NPVE functions?

http://www.vensim.com/documentation/fn_npv.html
http://www.vensim.com/documentation/fn_npve.html

sorry I forgot to attach the model

Still not possible to help you. You haven't provided the spreadsheet so we can see the calculations or instructions on what to look at.

I'd suggest making sure the model passes the units check before you start comparing it with other calculations.

My guess is that the equation for "harga sewa" is incorrect. You are accumulating the rate plus the level itself. This is similar to

x(t) = x(t-1) + x(t-1) + rate

I think the key problem here is indeed the equation for harga sewa. Currently it is:

INTEG( rate harga sewa+harga sewa, 25000)

but it probably should be

INTEG( rate harga sewa, 25000)

Units checking would reveal the error, if units were defined.