Weather Normalization

How Mestro implements degree days

Weather normalization can be seen as the the deviation of the average daily temperature from a reference period most often called "normal year" (a calculated average over a certain period of time). The amount of energy used for heating and cooling is strongly correlated with outdoor temperature, naturally. Normalizing heating and cooling data helps you assess the efficacy of a building's heating and/or cooling systems through times with varying outdoor temperatures.

How Mestro normalize using degree days (heating and cooling):

• Weather normalization data is collected from DegreeDays*, by default,

• The normal year is always calculated in the same way (an hourly average of the years 2005 through 2012),

• The base temperature for all properties in Mestro is 17 degrees celsius.

Mestro calculates a factor by dividing the degree days of the current year with the degree days of the normal year. The measured energy usage is then divided by this factor. Major variations in outdoor temperature will therefore be accounted for by this corrective factor. We apply SMHI's recommended rule for extreme months (max correction of 150% and minimum correction of 60%).

Activation of degree days for heating is applied automatically, but when it comes to degree days for cold meters, you need to contact your Customer Success Manager or Mestro Support.

Note: Degree days can also be collected from SMHI per request (however, SMHI charge for this. Contact support@mestro.com for more information).

Degree days in Mestro Portal

Degree days is a metric of how local temperatures deviate from the normal year. You can choose to normalize heating and cooling data in Mestro Portal by toggling the Weather Normalize switch in report settings, under the section Calculations.

Mestro Portal can visualize the degree days for a specific location if you limit input data to a single property, or several properties located in the same geographic area. Simply select Weather Normalization in the usage report. We are unable to visualize degree days for groups of properties located in cities served by different weather stations, unfortunately.

However, this does not limit your application of degree days calculations in reports. An advantageous example is in the ranking report, where you can compare normalized changes between cities/regions. By considering relative outdoor temperature, you can determine how well a property (or group) compares with others through time. See the example below. With normalized heating applied, it turns out that two municipalities (Kommunen Söder and Kommunen Central) achieved significant efficiency gains, while Katrineberg's usage increase was less dramatic than the absolute usage data indicated.

Note: Since degree days are calculated on a monthly basis, you cannot use the weather normalized heating or cooling in the Usage Analysis report if you want to look at hourly data.

Base load months

Usually, district heating is used for both heating the indoor climate and hot water. Under the Edit-tab you will find a section called Degree day data. There you can change the settings the control which months of the year weather normalization is applied. You can make the system ignore the month of July or June / August when normalizing. You can also pick a calculation type. Do you prefer percentages, base load months or do you have no preference?

There are two ways to tell the system how much district heating is used to heat water:

1. You can choose to deduct the amount of heating used during the summer by choosing the calculation type Base load months. You can then choose to deduct either the heating used in June / August or in July.

2. The second type of calculation is to select a certain percentage of the rolling 12-month heating and then subtract the amount divided by 12. This is a rolling calculation applied each month.

Hot water part (%) is used to configure a fixed deduction for heating hot water from total district heating. This percentage of usage is removed before running the weather normalization.

Finally...

We are a developing company and appreciate your feedback! If anything is unclear or you wish to share your ideas, don't hesitate to contact your Customer Success Manager or send an email to support@mestro.com. We are happy to assist you with Degree Days or SMHI weather normalization.