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A Look at some Key ENERGY STAR Concepts

March 1, 2021

Energy Star Portfolio Manager (ESPM) is the platform used by the Building Energy Challenge (BEC) for collecting and sharing data in the form of reports. This article provides information on a few key ESPM concepts so that you can make good use of them when analyzing your building.

Source Energy vs. Site Energy

Source energy is the amount of heat and energy consumed by your building, including losses that occur in the generation, transmission and distribution of energy.

Conversely, site energy is limited to the perimeter of the property. It takes into account only the energy consumed in the building. It is the heat, gas and electricity consumed by a building as reflected in your utility bills.

Source energy use intensity (EUI) is the ratio of energy consumption at source in a building as a function of its size (energy per square foot per year). That value is an indicator of the building’s energy performance, and includes the performance of the type of energy used.

Site energy use intensity is a building’s energy consumption onsite divided by its floor area. It is the most widely used building energy performance indicator because it represents the energy used onsite without any external correction. While EUI allows for the impact of the building’s surface area on its energy consumption, other factors can have an impact on the building’s energy consumption, particularly weather conditions. Standardizing EUI according to weather conditions thus makes it possible to compare the evolution of a building’s consumption over several years, and to also compare the consumption of several buildings.

 

ENERGY STAR Scores

The ENERGY STAR score allows you to compare the energy performance of your building with the performance of other similar buildings. The parameters of your building such as floor area, location and operating characteristics (type of use, hours of operation) are taken into consideration. Energy consumption is then standardized according to weather conditions and how the building is used, taking into consideration  EUI at source and then comparing the results with a portfolio of Canadian buildings similar to yours.

A number from 1 to 100 is attributed to your building. That is the ENERGY STAR score. The rating represents the ranking of your building, in other words the percentile associated with your building as compared to others in the building portfolio. For example, if your building has a rating of 5 (i.e. equivalent to the 5th percentile), that means that 95% of the buildings in the portfolio perform better than yours. Your building therefore has strong potential for improvement. Conversely, if your building obtains a rating of 80 (i.e. performance in the 80th percentile), that means that only 20% of the buildings in the portfolio are performing better than your building. Note that the ENERGY STAR score for your building can vary from year to year, as it depends on the buildings that make up the portfolio. If the median value of the portfolio is updated and improves, the rating for your building may decrease if its performance has stagnated. For the moment, the data used to determine the median values of the different building categories referenced by ESPM come from Canadian surveys and are determined on a basis of sampling. For certain building categories, American data are used due to a lack of Canada-wide information. Ultimately the ENERGY STAR score reflects the position of your building in relation to Canadian building stock and its evolution from one year to the next. For more about how ESPM determines ENERGY STAR ratings, consult the Portfolio Manager technical reference:  ENERGY STAR Score. Note that this score is neither required nor taken into account in the performance assessment by the BEC.

 

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