Three Easy Ways to analyze your Energy Usage with Degree Days

Good energy management is all about finding ways to keep costs down and efficiency up. To make sure you’re on the right track, you’ll need to regularly measure your progress.

The problem is that unless you have perfect control of your usage, there are external factors that will skew your results. Take temperature, for instance. If it was unusually cold or warm during a specific period, this may impact your energy consumption — and therefore your ability to compare year-on-year performance or make an accurate forecast.

The solution? Use Degree Days.

Degree Days (DD) are one of the best ways to analyze your energy usage. These are temperature-based figures that allow you to normalize (or correct) the impact of external factors like weather on your energy consumption.

Let’s clarify what DD are: A Degree Day is simply a measurement of how much (in degrees) and for how long (in days) the outside air temperature was either above or below a certain base point. The concept of degree days comes from meteorology. Degree Days allow you to calculate and compare the potential heating or cooling requirements of each year and each month in order to have a better understanding of how much heat or cooling you might need based on historical weather conditions.

For simplicity, we will refer in this article only to weather adjustment of energy usage by Degree Days. The methods can be used for analyzing heating or cooling usage as well as combined usage with the help of Heating & Cooling Degree Days (HDD & CDD).

What is required to do a weather correction of your energy usage?

To perform a weather correction of your energy usage, you need two things:

You have a series of energy bills or meter readings (the actual energy use) for your property. We’ll call these the “actual” bills or readings.
You also need a source of Degree Days for your location, such as energy-data.io. Enter your location in the calculator form and select a base temperature and period from the drop-down list.

Efficiency Ratio

Efficiency Ratios are a great way to benchmark your energy performance and track efficiency over time.

The Efficiency Ratio is a simple way to understand the weather-corrected energy performance: You just divide your usage by the sum of Degree Days in that specific period. The result will be a ratio or coefficient that you can compare with other periods: usage per Degree Day. If the coefficient declines, you became more efficient.

Although this method is easy and fast to implement, these ratios are not as easy to grab as kilowatt-hours.

Long-Term Average Normalization

The most common way to analyze your energy usage in relation to Degree Days is to compare it to a long-term average (e.g. 10 years) and correct your actual usage with this factor. The result will be weather-corrected kilowatt-hours

Base-Year Normalization

This approach is similar to the “long-term average” approach you put the sum of Degree Days of your reporting period into a comparison of a reference value. But instead of the 10-year-DD-value, you set one year of your reporting values as a base. For example, your started monitoring your usage five years ago, then you will set the first year as a base (100%) and correct every following period according to the variation of Degree Days.

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Calculate Heating Degree Days for various international locations using our free online calculator. Test the influence of the heating limit or compare different locations.

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