Degree days, explained
A heating degree day counts how far a day's average temperature falls below 65°F. A 40°F day adds 25. Add them up over a year and you get a measure of how much heating a place needs. Cooling degree days work the same way above 65°F.
Aeonis Leak uses NASA POWER's 2001–2025 averages for your area, so a home in a cold place shows a bigger heating stream than the same home somewhere warm.