Today’s NY Times has a graphic, comparing costs of various sources of electricity with and without a greenhouse gas tax (the tax could be a direct tax or the result of a cap and trade policy):
For larger image
I’m not sure what long-term expectations are about natural gas prices. A DOE graph shows natural gas oscillating between $6 and $8/million BTU this year, but natural gas ranged from $10 – 12 for several months in 2005.
With a $10/ton CO2 tax (again, this could be the result of a cap and trade policy), nuclear power is cheaper than all but natural gas, assuming $6/million BTU. Pulverized coal is a tad more expensive than nuclear, and gasified coal is 1 cent/kWh more expensive, as is natural gas with higher costs. Wind, biomass, and solar thermal are 3 – 6 cent/kWh more expensive (lowest estimate for solar thermal).
At $50/ton CO2 tax, coal is more costly than wind. By the time the tax reaches this level, the costs of solar thermal hopefully have fallen below coal’s cost in southern states, though today solar thermal could not compete.