# Right Approach to Calculating the Average of the Last Three Years of Consumption?

Greetings,

I’m trying to calculate the average of the last three years of consumption for the same period of previous years. For example, the current Max Month is August 2022 so I’ve calculated the following:

DAX:

``````Consump YTD Same Period Three Year Avg =
VAR MaxMonth = [Max Month]
RETURN
CALCULATE ( [ConsumptionYTD (kgal)], Dates[MonthOfYear] <= [Max Month] )
``````

Each year’s total is through August. Good stuff. But I can’t figure out how to filter the last three years using DAX, sum them up, and divide by a dynamic three-year interval.

Is this the right approach to the problem? I’ve tried using DATESINPERIOD rolling average approach but the result is an average for every billing date in the fact table.

This will be an intermediate calculation used in other measures.

Thanks!

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I’m almost there. The following DAX:

``````Consumption last three years =
CALCULATE (
SUM ( ConsumptionData[Consumption (kgal)] ),
DATESINPERIOD ( 'Dates'[Date], MAX ( 'Dates'[Date] ), -3, YEAR )
)
``````

Results in:
2020 Total Consumption
2021 Total Consumption
2022 YTD Consumption (Through Max Date August 31st 2022)

I can’t figure out how to combine the filtering used in Post #1 with this Measure to filter Years 2020 and 2021 for the same period as 2022 and get a total. The resulting value should be 6,814,294.

Success!

``````Avg Consumption Previous Three Years =
VAR MaxMonth = [Max Month]
RETURN
DIVIDE (
CALCULATE (
[Consumption-Total],
Dates[MonthOfYear] <= MaxMonth,
DATESINPERIOD ( 'Dates'[Date], MAX ( 'Dates'[Date] ), -3, YEAR )
),
3
)
``````

Thanks for sharing your solution, @RandyS