The least bad option is a comprehensive carbon tax that applies to all hydrocarbon fuels, from gasoline to propane. It gives each consumer the freedom to determine the energy use that best suits his or her budget. But is it fair? Only if it is revenue neutral, that is, if the extra tax income is offset with lower taxes elsewhere.
Of course, when you tax energy, you're in essence punishing those who are trying to make an easier life for everyone.
Certainly a good 'tree-hugger' idea, but not a well-thought out tax, in my opinion.