It’s fairly easy to assess the electricity consumption of your home using a smart meter, but what can you do to find out exactly how much electricity your air conditioning and furnace consume? Calculating heating degree days (HDD) and cooling degree days (CDD) shows the fuel consumption of each piece of equipment to determine efficiency performance. Once you know that, you can better evaluate how much energy savings you’ll recoup from upgrading.
Degree days are a measurement of how much heating and cooling is necessary on a given day, which is essential to figure out because weather demands vary from one year to the next. If winter in 2011 is particularly harsh, heating demands may increase. Comparing this coming winter’s utility bills against last year’s milder winter demands won’t result in an equal comparison. If you calculate heating degree days from 2011 and 2010 against both years’ utility bills, you’ll get a more accurate assessment of efficiency.
The same can be said of cooling degree days. If you’re looking at investing in higher-efficiency air conditioning, you can evaluate the efficiency of your old system and compare it to EnerGuide or Energy Star labels for expected savings.
To calculate degree days, use a baseline temperature of 15.5 degrees (a temperature where most people are comfortable). Taking the high and low temperatures of a particular day, find the average. If the average equals 18 degrees, then the CDD for that day is 2.5. This is calculated by subtracting the baseline from the average. (HDD are calculated by subtracting the average temperature from the baseline).
To find the CDD for the summer, add up each day’s CDD and look at the electricity consumption for that season. Or, to easily calculate degree days for specific locations, there are online programs available. Calculating CDD over the course of several years shows you how an air-conditioning system performed with regard to efficiency. It can also reveal how regular preventive maintenance helps it to perform well each year.
For help with evaluating heating and cooling efficiency and finding higher-efficiency equipment, contact Arpi’sexperts. We are industry leaders in Calgary, and we know how to help you get significant results from your investment.
Our goal is to help educate our customers about energy and home comfort issues (specific to HVAC systems). For more information about degree days and other HVAC topics, download our free Home Comfort Resource guide.