Cooling Degree Days Calculator

Enter Average Daily Temperature (Tavg) in °F:



Enter Base Temperature (Tbase) in °F:



Calculate

Cooling Degree Days (CDD):

The Cooling Degree Days (CDD) Calculator is a useful tool for estimating the demand for energy used to cool buildings. It helps in understanding how much cooling is needed based on outdoor temperatures. By comparing the average daily temperature to a standard base temperature, CDD helps homeowners, utility companies, and HVAC professionals measure cooling requirements over time.

Formula
The formula to calculate Cooling Degree Days is:
Cooling Degree Days equal the average daily temperature minus the base temperature. If the result is negative, CDD is considered zero.

How to Use

1. Measure or find the average outdoor temperature for the day (Tavg).
2. Use the standard base temperature (Tbase), often 65°F in the U.S.
3. Enter both values into the calculator.
4. Click “Calculate” to see the Cooling Degree Days.
5. Use the result to estimate cooling energy usage.

Example
If the average daily temperature is 80°F and the base temperature is 65°F:
Cooling Degree Days = 80 - 65 = 15
This means 15 cooling degree days were recorded for that day, indicating higher cooling demand.

FAQs

1. What are Cooling Degree Days (CDD)?
   They measure how much (and for how long) outdoor temperatures are above a base temperature, indicating the need for air conditioning.
2. What is the common base temperature used?
   Typically, 65°F is used in the United States.
3. Can the CDD be negative?
   No, if the average temperature is below the base, CDD is recorded as zero.
4. Why is this calculation useful?
   It helps predict energy consumption for air conditioning systems.
5. Who uses CDD data?
   Utility companies, building managers, homeowners, and HVAC engineers.
6. Can I calculate monthly or yearly CDDs?
   Yes, by summing the daily CDDs over a month or year.
7. Is this only for the U.S.?
   No, it’s used worldwide, though base temperature may vary by region.
8. Can I change the base temperature?
   Yes, adjust Tbase to reflect the comfort level or local standards.
9. Does CDD affect energy bills?
   Yes, higher CDDs usually mean more cooling and higher energy consumption.
10. What happens if I enter non-numeric values?
    The calculator will display "Invalid input."
11. How accurate is the CDD calculator?
    It provides a good estimate but assumes consistent indoor temperature needs.
12. Is this related to Heating Degree Days (HDD)?
    Yes, HDD is the opposite—used for measuring heating needs when it's cold.
13. Is this calculator mobile-friendly?
    Yes, it works on any device with a modern browser.
14. Can I use it for educational purposes?
    Absolutely, it's great for teaching weather and energy concepts.
15. Does this replace professional HVAC planning?
    No, it's a helpful tool but not a substitute for professional advice.
16. Can I embed this on my website?
    Yes, the HTML and JavaScript can be added to any web page.
17. What’s the best way to collect average daily temperature?
    Use data from local weather services or home weather stations.
18. Does humidity affect CDD?
    No, CDD is based only on temperature, though humidity can affect actual comfort.
19. How often should I calculate CDD?
    Daily calculations give the most accurate picture over time.
20. What are some limitations of CDD?
    It doesn’t account for insulation, humidity, or internal heat sources.

Conclusion
The Cooling Degree Days Calculator is a straightforward and practical tool for understanding energy needs related to cooling. Whether you're tracking your home's efficiency or managing a large commercial building, CDD helps forecast energy usage and costs. With just a few inputs, you can make better decisions about air conditioning and energy consumption throughout the year.