If you use natural gas to heat your home, weather affects the amount of gas you use, and therefore, the total amount you pay on your gas bill. To determine the impact of weather, natural gas utilities use a measure called heating degree-days.
We start counting degree-days at the beginning of the heating season, and keep adding them up for each 24-hour period until the heating season ends. Degree-days are counted whenever the daily average outdoor temperature falls below 18°C (64°). For example, if the average temperature during a 24-hour period is -10°C, then 28 degree days would be counted for that one day. Degree-days are not calendar days; there can be many degree-days in one 24-hour period. The colder it is outdoors, the greater the number of degree days and the more natural gas you will use to heat your home.
The colder the temperature is outside, the harder your furnace has to work to maintain a comfortable temperature inside, even if you don’t turn the thermostat up. As a result you will consume more energy (natural gas, oil or electricity) to keep your home at a comfortable temperature. Plus you’ll spend more time indoors and use more energy overall. Rest assured, though, that natural gas is the most efficient choice for your home heating and water heating needs.