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is it possible to model building electricity demand in energy plus?

asked 2021-07-07 09:17:03 -0500

Hardik's avatar

updated 2021-07-09 16:48:02 -0500

I have simulated a building prototype model in energy plus. also, I have got building electricity from meter object. In that model, I have sets some data in electrical equipment, lights etc..( internal gain ) and external lights such as equipment schedule name and put watt value in design level. still, I do not understand about generated electricity data from the meter object in energy plus ? is it realistic electricity demand in that model or some converted value from thermal demand? I would like to get some clarification on this confusion.image description

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@Hardik can you include a table or image of the results you have questions about?

Aaron Boranian's avatar Aaron Boranian  ( 2021-07-07 10:12:55 -0500 )edit

Thank you for your response. here, I have attached the result sheet from my model. I have simulations values of electrical, space heat, domestic hot water on an hourly basis (row 8760). but, I do not understand that ' how building electricity is estimated ?' which processes energy plus use to calculate electricity in the building model.

Also, I would like to inform you. I have used Schedule:Day: Hourly fraction values from Energy plus prototype model. Could you a little bit explain about the connection between fraction values and ( Lights, Electrical Equipment, Exterior Lights )

Hardik's avatar Hardik  ( 2021-07-08 02:49:40 -0500 )edit

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answered 2021-07-08 14:57:10 -0500

sashadf1's avatar

updated 2021-07-08 15:26:49 -0500

The Schedule:Day:Hourly fractional values are multiplied by the design wattage of equipment, lights, or exterior lights to calculate the instantaneous power drawn by the equipment, lights, or exterior lights.

See here: "The electrical input for lighting in a particular timestep is the product of the design level and the value of this schedule in that timestep." See Field: Lighting Level to assign the "maximum electrical power input (in Watts) to lighting in a zone." "This value is multiplied by a schedule fraction to get the lighting power in a particular timestep."

See here for Electrical Equipment:; there is a similar process for calculating the electricity draw at the particular timestep. "The actual electrical input for equipment in a zone as defined by this statement is the product of the design level field and the value of the schedule specified by name in this field."

Electrical Equipment Design Level: "This field (in Watts) is typically used to represent the maximum electrical input to equipment in a zone that is then multiplied by a schedule fraction."

The schedule value can vary from hour to hour.

I can't find a similar block of documentation for exterior lights, but maybe you can. The lights block of documentation may cover external lights as well.

As for your question about how building electricity use is calculated, open up the eplusout.mtd (meter details output) file in your simulation results folder. Search for Electricity:Facility [J] and Electricity:Building [J] to see exactly what variables are on those meters.

For example, after searching, I find a block of code that says, "For Meter=Electricity:Facility [J], ResourceType=Electricity, contents are:" ...... a bunch of eplusout.rdd variables and/or other meters.

Another search finds, "For Meter=Electricity:Building [J], ResourceType=Electricity, Group=Building, contents are:" ...... a bunch of eplusout.rdd variables and/or other meters.

On inspection, the difference between Electricity:Building [J] and Electricity:Facility [J] is that Electricity:Building [J] does not contain HVAC related energy.

See more about the split of HVAC versus non-HVAC power demand here:

"Electric:Facility contains all electricity from internal loads and HVAC systems. Electricity:Building only contains electricity from internal loads (lights, electric equipment, etc).

Please check the green checkmark next to the answer if this is satisfactory.

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Asked: 2021-07-07 09:17:03 -0500

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Last updated: Jul 08 '21