Drying clothes in a gas or electric dryer is energy intensive. An electric dryer uses about 2.3 KWH of electricity to dry one load. In addition, as the dryer vents its exhaust out of the house, new air is pulled into the house to replace it, and in the winter, this new air must be heated. If the temperature outside is (say) 30F, it takes aboutanother 2 KWH to heat this incoming air. In climates where AC is used in the summer, air pulled in by the dryer must be cooled. So, drying one load can takes from 2.3 KWH to 4.3 KWH for each load -- a lot. If you do a load a day, then you probably spend about 1000 KWH per year on drying energy.
I'll figure 200 loads in a year, for a two-adult household. Without AC, figure 860 KWH. Do the Math on that.
One therm is 29.3 KWH and 12 pounds CO2. 860 KWH is 29.4 therms and 350 pounds of CO2. If I save half of that, it is about fifteen therms, $30, 180 pounds CO2.