Your Dedicated Design Day Capacity (DDDC) factor is based on how you use natural gas to heat your home on the coldest time of the year vs. how you use natural gas in the summer. You can lower your DDDC by being mindful of how you heat your home. Use the correct thermostat settings for winter to cut your natural gas usage. You should also perform a DIY home energy audit to find and fix where you're wasting heat. Watch the weather reports to keep track of cold weather and conserve energy on those days.