Degree Days and Building Balance Points Help Predict Energy Usage
Posted on Wed, Oct 26, 2011 @ 10:21 AM
Joe Zaworski | jzaworski@tesengineering.com
When the term degree-days appears on your gas bill, you may wonder what the term means and how the figure was derived.
We apologize, but before we define degree-days, we need to define balance point.
Another tool useful in understanding how weather can effect energy consumption is a building’s balance point. Simply, the balance point for a particular building is the outdoor temperature at which the building does not require any heating or cooling. It’s kind of like the tipping point of a scale, with heating energy on one side and cooling energy on the other.
The building’s balance point is determined in graphical form as a function of energy consumption and ambient temperature. Fitting a trend line to this utility data allows one to determine when a building requires either heating or cooling.
Degree-days are the sum of degrees above or below a building’s balance point temperature in a given period of time, most commonly a day, a month or a year. The cooler the weather is, the more heating degree-days there are (resulting in increased demand for heating energy). The warmer the weather is, the more cooling degree-days there are (resulting in increased demand for cooling energy).
While this number can determine weather-related patterns in heating and cooling usage, at the same time, it alerts one to problems with older HVAC equipment or energy savings impact of new HVAC equipment. With historic degree-day data in hand, it will be easier to identify anomalies in building operations and malfunctioning controls or equipment.
When looking at a gas bill, one can see the amount of gas-consumed correlates with the number of degree-days in that month. To ensure the building’s equipment is operating correctly, verify the higher consumption relates to more degree-days.
Degree-days and balance points are two useful tools to track demand for energy used by heating or cooling equipment. For more information concerning degree-days, balance points, or general facility operations, contact TES Engineering.
