Tariff Analysis - Ratchet

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Ratchet tab on Tariff Analysis dialog


The Ratchet object allows the modelling of tariffs that include some type of seasonal ratcheting. Ratchets are most common when used with electric demand charges. A ratchet is when a utility requires that the demand charge for a month with a low demand may be increased to be more consistent with a month that set a higher demand charge.


DropDownClosedExample: A utility has a single ratchet that says that the billing demand for each month of the year is the higher value of the actual demand or 60% of the peak summer demand.


DesignBuilder input :



EnergyPlus idf:




If multiple ratchets occur in the same tariff, they be “chained” together with the Baseline source variable replaced with the Ratchet variable name of the previous Ratchet.

Ratchet variable name

This entry defines the name of the ratchet and the variable that stores the result of this ratchet. The ratchet variable name should be used wherever the ratchet should be applied and is often the source variable for Simple or Block charge objects.

Baseline source variable

The name of the variable used as the baseline value. When the ratcheted value exceeds the baseline value for a month the ratcheted value is used but when the baseline value is greater than the ratcheted value the baseline value is used. Usually the electric demand charge is used. The baseline source variable can be the results of another ratchet object. This allows utility tariffs that have multiple ratchets to be modelled.

Adjustment source variable

This field defines the variable that the ratchet is calculated from. It is often but not always the same as the baseline source variable. The ratcheting calculations using offset and multiplier are using the values from the adjustment source variable. See the bottom of this section for how ratchet works.

Season from

This is the name of the season that is being examined. The maximum value for all of the months in the named season is what is used with the multiplier and offset. This is most commonly Summer or Annual. When Monthly is used, the adjustment source variable is used directly for all months.


The choices are:


Fall (Autumn)

Season to

This is the name of the season when the ratchet would apply. This is most commonly Winter. The ratchet only is applied to the months in the named season. The resulting variable for months not in the Season To selection will contain the values as appear in the baseline source variable. The choices are:


Fall (Autumn)

Multiplier value or variable name

Often the ratchet has a clause such as “the current month demand or 90% of the summer month demand”. For this case a value of 0.9 would be entered here as the multiplier. This value may be given as one if no multiplier is needed. This can also be a variable name, which should be defined on User variables tab.

Offset value or variable name

A less common strategy is to say that the ratchet must be all demand greater than a value, in this case an offset that is added to the demand may be entered here. If entered, it is common for the offset value to be negative representing that the demand be reduced. The value can be zero if not offset is needed in the ratchet. This can also be a variable name, which should be defined on User variables tab.

Detailed step taken for ratchet calculation

AdjSeasonal contains either:
oWhen SeasonFrom is not set to Monthly, the maximum for all months in Season From in the Adjustment Source Variable. This is a single value.
oWhen SeasonFrom is set to Monthly, the monthly values of the Adjustment Source Variable.
AdjPeak = (AdjSeasonal + Offset) * Multiplier
MaxAdjBase = maximum value of either AdjPeak or Baseline Source Variable
The resulting Ratchet Variable contains:
oFor months not in SeasonTo, the values of Baseline Source Variable
oFor months in SeasonTo, the values of MaxAdjBase




For a simple typical case using totalDemand for both “Baseline source variable” and “Adjustment source variable”, please see the example at the top of this page.