• Reflects how warm or cold it was during a specific period.
• The larger the number, the colder the temperature was.
• You usually use more heating fuel in colder weather because your furnace is working harder to maintain comfortable temperatures.
• Degree day calculations are based on the assumption that a building does not require any heat if the outside temperature averages 65 degrees during a 24-hour period.

Calculate degree days:

1. Add the highest temperature to the lowest temperature for the period.
2. Divide the total by two.
3. Subtract the result from 65.

Example:

If the day's high temperature was 30 degrees and the low was 10 degrees:

Use degree days to compare energy consumption for a given time period:

• Calculating your energy use per degree day will reduce the weather impact on your comparison.
• To find natural gas use per degree day, divide the number of therms used by the number of degree days for the same period.

Example therms for an example home:

• 146 therms for the billing period in December 2001.
• 239 therms for the billing period in December 2002.

Degree days for example billing period:

• 724 degree days during the December 2001 billing period.
• 1,222 degree days during the December 2002 billing period.

Natural gas use per degree day:

• .20 in December 2001.
• .195 in December 2002.

This home was using energy more efficiently in December 2002.