Sadly, the clothes line math error is in the direction of lesser justification for savings effort. The math of Build It Solar is quite correct. Further math for understanding is correct at my web site: Convert KWH at 29.3 KWH per therm and 12 pounds CO2 per therm. About 410 pounds of CO2 results from generating 1000 KWH. Here is one credible outside source for the conversions. The 410 number looks right for the Northwest mix of sources, mainly coal and hydroelectric.
Numbers above are from the UC Irvine link.
Allow that my two-person household would be using 860 KWH per year with full resort to an electric dryer. Saving half of that is 180 pounds of CO2 and $30 at $2 per therm, per year. Savings are smaller (by half?) where I have a natural gas dryer.
The error found? It is in the often-cited CS Monitor article. Annually, these dryers consume 1,079 kilowatt hours of energy per household, creating 2,224 pounds of carbon-dioxide emissions.
1079 KWH converts to perhaps 440 pounds of CO2.