It’s a Matter of Degrees

By Nicholas Sakelaris | May 28, 2025

WEATHER is the biggest factor affecting your electric bills.

The hotter it is, the more energy it takes to cool your space. But it can be difficult to gauge its direct impact on your bill. Utilities, like CoServ and the government, use a measurement called Degree Days that makes it easy to compare one day, one week, one month, or season to another.

Calculating Cooling Degree Days (CDD)
To calculate CDD, find the average temperature for the day and then subtract 65 from it to get the CDD.

Cooling Degree Days
(CDD)

Used when the outside temperature is ABOVE 65

Heating Degree Days
(HDD)

Used when the outside temperature is BELOW 65

Average
Outside Temp

90°

Minus Optimal
Outside Temp

65°

CDD

25°

Average
Outside Temp

90°

Minus Optimal
Outside Temp

65°

CDD

25°

Do this calculation for each day to get the total CDD for the periods you want to compare. This allows a quick comparison of one period to another and shows the impact summer heat has on energy use.

May 2024 had 386 total CDD versus June 2024 which had 585 total CDD. This is a 52% increase in air conditioner use, which means a higher electric bill.

Need more information? For more information, please visit CoServ.com/DegreeDays to watch our explainer videos.