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How to model a Utility Tariff with different schedules for Energy vs Demand

asked 2021-07-09 14:36:08 -0500

Mohammad gravatar image

updated 2021-07-09 16:31:16 -0500


I'm wondering if anyone could assist with utility tariff modeling- for a case that Energy Charges come with a different schedule compared to the Demand Charges.

My initial thought was about adding a second UtilityCost:Tariff object that could represent the demand schedule (and assign the energy schedule into the first UlityCost:Tariff object); and then create UtilityCost:Charge:Simple for both Energy and Demand.

However, this option did not work, as I have to leverage UtilityCost:Qualify, in order to be able to select between different scenarios with different demand thresholds. In other words, I have to stick into one UtilityCost:Tariff in order to takes benefits of UtilityCost:Qualify.

Any help would be greatly appreciated. Thanks!

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Could you explain a little more what you mean when you say "different schedules"?

JasonGlazer gravatar image JasonGlazer  ( 2021-07-09 14:59:44 -0500 )edit

Thank you so much for getting back to me. Sure! For instance, my winter schedule for Energy is like this (as you know, 1 stands for on-peak, 3, off-peak, and 4 :mid-peak):

Through: 5/31,
For: AllDays,
Until: 6:00,
Until: 8:00,
Until: 21:00,
Until: 24:00,

However, my Demand schedule for winter is:

on-peak at Weekdays (4-9 pm)

off-peak: all other hours

Thanks, Mohammad

Mohammad gravatar image Mohammad  ( 2021-07-09 16:02:21 -0500 )edit

Have you looked that E+ example files for tariffs? I'm (almost) certain that energy and demand schedules are independent of each other, and that you can set a schedule for each one

Jim Dirkes gravatar image Jim Dirkes  ( 2021-07-11 16:00:44 -0500 )edit

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answered 2021-07-12 07:17:25 -0500

A single UtilityCost:Tariff will work following the approach used by Example F in the InputOutputReference documentation and 5ZoneEconomicsTariffAndLifeCycleCosts.idf. The general way to solve this problem is to segment a single schedule to represent all the different times that matter for your tariff and then use a special "Native Variable" as shown in the Tariff Report for the segments that you need which include combined segments such as PeakAndMidPeakEnergy or PeakAndShoulderDemand.

Specifically, for your schedule, I would define the times as:

  • until: 6:00, 3 (offpeak)
  • until: 8:00, 4 (midpeak)
  • until: 16:00, 1 (peak)
  • until: 21:00, 2 (shoulder)
  • until: 24:00, 4 (midpeak)

For energy, create UtilityCost:Charges:Simple that uses Source Variables for OffPeakEnergy, MidPeakEnergy, and PeakAndShoulderEnergy.

For demand, create UtilityCost:Charges:Simple that uses Source Variables for ShoulderDemand.

The native variable PeakAndShoulderEnergy combines the energy for both the peak and shoulder periods. You can see this and others of these NativeVariables shown in the tabular output TariffReport.

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Awesome! Thank you so much! Just one more related question. Would you please let me know how to model a demand charge called Facilities Related Demand (FRD) charge? Such component represents the kW of Maximum Demand recorded during (or established for) the monthly billing period.

Mohammad gravatar image Mohammad  ( 2021-07-12 10:30:12 -0500 )edit

If you want it based on the monthly peak demand just make another UtilityCost:Charges:Simple and use the TotalDemand as source variable.

JasonGlazer gravatar image JasonGlazer  ( 2021-07-12 10:55:40 -0500 )edit

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Asked: 2021-07-09 14:36:08 -0500

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Last updated: Jul 12