Heating/Cooling Degree Days

One of your recent questions for the blog was "what are heating degree days and cooling degree days, and what use are they to me?"

It's a good question, as you probably see this information in the weather section of your local paper every day.

First, how they're calculated.

Heating Degree Days are determined by subtracting the mean temperature for the day (high+low/2) from 65 degrees. The result is the number of heating degree days. Public utilities and HVAC professionals can use these numbers, compiled over the long-term to determine how much energy will be needed to keep homes and businesses warm through the cold season. (One example is that New York City averages about 5000 heating degree days per season, while Barrow, Alaska averages over 20,000).

Cooling Degree Days follow a similar form, but are used to estimate the amount of energy it takes to cool homes during the warm season. To calculate them, you subtract 65 degrees from the daily mean temperature (formula above).

A cumulative total is kept for each year, allowing the pro's and the energy conscious to estimate the amount of energy required to heat and cool buildings and homes each year.

Colorado Springs averages 6415 heating degree days each year. For Pueblo, the figure is 5413, so in a "normal" year, it's less expensive to heat a home in Pueblo, than in Colorado Springs.

For the warm season, the roles are reversed:
Colorado Springs averages 419 cooling degree days each year, while Pueblo averages 973, which means that in a typical year (if you're lucky enough to have a swamp cooler or air conditioner), you'll spend less energy dollars in Colorado Springs and more in Pueblo.

You can find your local average heating and cooling degree days at degreedays.net, and you'll also find some great references to articles that will tell you more.

Most of us won't use these figures, but they're VERY helpful to professionals involved in the energy, heating and cooling trades.

Keep those questions coming.
M