A carbon tax figure often mentioned is $25 per ton of carbon dioxide. That would add about $.25 to a gallon of gasoline, about $.005 to a kilowatthour of electricity. But again, this money is intended to be redistributed to produce a net-zero increase in federal taxes, and so it merely induces greater use of alternative energy and more efficient devices. In that way, it is credited with domestic and international success in driving the economy forward toward ever-improving technology.
The primary argument against a carbon tax is that it would detrimentally effect the fossil-fuel economy. However, the average cost of a barrel of oil has declined by half and with Iran returning to the market the glut of its oil will likely keep prices low for years to come. Similarly, the price of natural gas is at historic lows with more reservoirs being regularly discovered. With the reductions in the cost of this fossil fuel energy, the carbon tax will not be significantly noticed by the consumer.
Oil and natural gas account for the majority of all carbon dioxide emissions. Because of the low price of these commodities, their use may expand, to the detriment of renewable energy production, to the detriment of our health (the cost of adverse health effects due carbon fuel pollution is estimated at $120 billion annually), and to the detriment of increased global warming (the cost of harm caused by global warming is estimated at $2 trillion annually). And the estimates of the damage caused by fossil fuel pollution is only increasing as the estimates become more accurate -- and, the cost of species extinction is incalculable.