What is the definition and can I modify the EnergyCharges in the Group:Economics of EnergyPlus?

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Hello, I am trying to properly calculate the energy tariff of the property through EnergyPlus using the UtilityCost:Tariff and UtilityCost:Charge:Simple. I am having a difficult time finding information on how to decide what variable to use in the Source Variable field and also finding what is the definition of EnergyCharges in the Category Variable Name, what variables actually go into said variable, and can I modify what variables actually go into the tariff calculation? (which electricity charges, which items, etc)

Thank you! Best regards, Hanif