Checking "Use Improvement" changes savings

[LV Auditor]

I want to add window film on some west windows.  Before I check “use improvement” it shows a savings.  When I check “use improvement,” or the “current” column in the Improvements screen, the amount of savings changes to not cost effective.  It looks like a good improvement until I try to select it.  See the different in the 2 screenshots, first where windows are included, next when they aren’t.  What is happening?

[Gamaliel Lodge]

There are several reasons why the “checked” and “un-checked” numbers will almost never be identical.  This is partially by design and partially due to modeling limitations. However, this is an unusually large discrepancy. I would like to review this file, before giving you my full explanation. Please open the file and submit an error report.  You can assign it directly to me, by typing “gamaliel” in the Assign To field.

[Gamaliel Lodge]

As I suspected, there is an error impacting the savings displayed on the window row.  However this error does not impact the total package savings.  I will explain why that is below.  We will get out a patch later today to correct the problem.

OptiMiser simultaneously runs two very detailed models, one for the base building and one for the building with the proposed improvements in place.  This ensures that the total package savings are calculated using our most robust model.  Additionally OptiMiser runs a unique, but simpler model for each improvement measure that is represented by a row on the Details table.  These models estimate the impact of adding/removing each improvement to/from the selected package.  When an improvement is un-checked the savings on the row estimate the change to the total package savings incurred by checking the improvement.  However, once an improvement is added to a package, the savings on it’s row are an apportionment of the total package savings.  The two numbers will usually be slightly different due to interactions between the improvements in the package.

Running complete models for each measure would be too burdensome for a typical users computer, making OpitMiser unusable. The simple models are designed to incorporate the most significant interactions between the components and generate good individual savings estimates without bogging down your computer.  These simple models allow us to give you the dynamically updating measure-by-measure savings information that makes the Details table so interactive and allows us to quickly calculate optimized packages on the Packages tables.  Because these models are simpler than the detailed models used to generate the base and selected package models, the savings estimate of an un-selected item will often be slightly different, then the actual change to savings of the selected package to the realized by adding the improvement.

However, in any case where you see a disconcerting discrepancy between either the checked and unchecked savings, or the unchecked savings and the actual change to the package savings, then it is a good idea to submit an error report.  This will always help us to improve our estimates.

 

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