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Energy Related Costs, Annualized

asked 2018-09-12 12:18:15 -0500

erickp gravatar image

updated 2018-09-13 03:32:16 -0500

Our company is doing analysis on different products (i.e. different wall configurations where we are just changing 'wood stud', 'wall sheathing', and 'air leakage' parameters). Therefore, we are just creating separate cases and not using the parametric function because there are too many outputs, and not using the optimization function because it isn't really applicable for this exercise.

When I run a simulation with Analysis=design and Reference=My design, I get an output of ('energy related costs, annualized' = 801USD, and 'CO2 emissions'=4.59 metric tons/yr).

However, when I run this same case against a different reference, I get an output of ('energy related costs, annualized'=951USD & 'CO2 emissions' = 4.59 metric tons/yr) for the same analysis=design, and the reference=user defined (a lower performing envelope) is ('reference = my design' is 'Energy Related Costs' =822USD & 'CO2 Emissions' = 4.68 (Metric tons/yr).

MY QUESTION: When I compare 'analysis' to itself (i.e. a pure simulation) I get one output for, but when I compare 'analysis' to a different 'reference', I get another output with the same parameters for that same configuration being analyzed. Why does this change?

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Can you email your project file to beopt@nrel.gov?

shorowit gravatar imageshorowit ( 2018-09-12 13:33:38 -0500 )edit

I just sent it. You can give me a call on my cell phone on signature line to discuss. -Thank you

erickp gravatar imageerickp ( 2018-09-12 13:51:44 -0500 )edit

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answered 2018-09-13 09:41:09 -0500

updated 2018-09-13 10:04:11 -0500

The definition of Energy Related Costs, Annualized in the BEopt help file reads: "Annualized energy related costs, the default y-axis metric on the Cost/Energy Graph, are calculated by annualizing the energy related cash flows over the analysis period. The annualized cost is then subtracted from the reference for every cash flow but utility bills (i.e. the values displayed in the Cost/Energy graph are full annualized utility bills plus incremental annualized values for every other cash flow)."

The important fact here is that most costs are incremental relative to the reference building. So if you have a design that is also set as the reference, all incremental cash flows (including measure costs) are zero and only the annualized utility bill is displayed. When the design is compared to a different reference, then there are incremental cash flows (including measure costs) in addition to the annualized utility bill.

For this reason, you can't really compare Energy Related Costs, Annualized across different cases unless the same reference is used in all of them. If you do want to compare across cases with different references, you could use the Energy Related Costs, Life Cycle Cost metric instead where all cash flows are absolute (not incremental).

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Thank you so much! This really helps illuminate a few issues with past simulations. -Cheers

erickp gravatar imageerickp ( 2018-09-13 11:52:53 -0500 )edit

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Asked: 2018-09-12 12:18:15 -0500

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Last updated: Sep 13