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Weather Normalization Report Explanation Sheet

The Weather Normalization Report is designed to give users only a general estimate of the effect of weather on utility consumption from year to year and a general estimate of any possible utility usage avoided from year to year. This report does not provide information which measures or validates the success or failure of current or past facility utility and energy management or any conservation initiative.


This report does not calculate exact savings (Cost Avoidance) from any conservation effort performed in any facility. This report should not be used to make any type of energy conservation decision as there are many variables beyond the scope of this report that must be considered for such a decision. It is recommended that a Certified Energy Manager or Engineer be consulted for assistance with calculating utility and energy use savings and making energy conservation decisions or investments.

Weather Normalization Report Process


In the Report table above we will use July as the example month.

  • Step 1 For both the evaluation and baseline year, add cooling degree days (CDD) and heating degree days (HDD) to get total degree days (TDD) in each month using weather data for building’s associated weather station.
    • Base Year (July 2012): 246 TDD
    • Evaluation Year (July 2013): 182 TDD
  • Step 2 For each month, calculate total degree day (TDD) percentage difference between evaluation year and baseline year.
    • (Evaluation Year TDD – Base Year TDD)/ Base Year TDD
    • 182 – 246= -64/246= -.2602 or -26.02% (Degree Day % Difference)
  • Step 3 Multiply the degree day percentage difference between Evaluation year and Baseline year times Actual monthly usage in Baseline year. This step is performed on each month’s usage in the baseline year. This yields usage adjusted for weather, or the Normalized Use.
  • Step 4 For each month in baseline year, add Normalized usage in Step 3 to Actual monthly baseline usage to yield Total Normalized Usage in baseline year.
    • Actual Base Use: 10,000 so following step 3: 10,000 x -.2602 = -2,601.63
    • Normalized Use: 7,398.37 found by following step 4: 10,000 + -2,601.63=7,398.37
  • Step 5 Subtract the Normalized usage in each month of the baseline from Actual Usage in each month of the Evaluation Year. The net difference is Usage Avoidance. A positive number means usage was added.
    • Normalized Use: 7,398.37
    • Actual Evaluation Use: 7,000
    • 7,000 – 7,398.37 = -398.37 KWH (Use Avoidance)


A Negative Number is good. It means usage was avoided compared to the Weather Normalized Usage from the Baseline Year.


A Positive Number is bad. It means usage actually went up compared to the Weather Normalized Usage from the Baseline Year.