From a discussion here:

http://gristmill.grist.org/story/2006/1/23/233434/091#11

Capacity factor measures how many kwh (kilowatt hours) a system produces in a given time period compared to how many kwh that the rated power of the system would produce in that same time period under continuous operation.

A coal fired plant typically produces  80% of what it's rated power running continuously would produce.  The site says nuclear is 90%, but what about downtime for maintenance?

Does cutting that 28 foot square opening in containments and replacing inner workings  take months or years?

Wind and solar are typically 30% due to variability of the energy source. 

So what does this mean?  It means that cost per watt of generating capacity tends to be difficlt to compare between generating  systems.

So it is easier to compare kwh per year, rather than power ratings or capacity factor.  That is how wind power contracts are negotiated and verified.

A typical home uses about 10,000 kwh per year.  A 12 foot wind generator operating in 12 mph average winds will produce about 3,000 kwh per year.  That solar panel on the New Jersey home mentioned on my blog produces about 7000 kwh per year.

His panels have an 8.5 year payback period in energy bill savings.  The wind generator would be similar in payback and most of the average home's power use could be obtained from a dual system of this type.

 With solar cogeneration heating domestic hot water and helping a geothermal heat pump provide home heating and cooling, the whole system would produce enough of a surplus of electric power to charge an electric vehicle for household use.

Wind and solar can be scaled up to provide commercial transportation, manufacturing, and heating/cooling energy by installing it on roofs, over parking lots, farms, and industrail sites.

The largest wind machine kwh production levels indicate that the generating capacity needed to power half the present capacity of 600,000 mega watts  (the equivalent of 600 typical nuclear reactors), 300,000 megawatts, could be provided by 15,000  1,000 foot wind machines.

The 15,000 square miles that these machines would be distributed on would constitute less than 2% of the very high windspeed area in the nearly deserted northern great plains.  And 98% of that land area would not be used, only rudimentary roads and the tower bases would be actually used.

Nuclear plants come in at 2,3,4 dollars per watt of generating capacity.  Who knows how high the cost will go, given the fact that new plants are so far impossible to site and finance in the wake of Cherbobyl, Three Mile Island, and revelations about widespread radioactive contamination at various government owned, nuclear industry contractor run, sites like Hanford, Oak Ridge, Rocky Flats ...and on and on.

The equivalent generating capacity per watt from wind (factoring in the 30% versus 80% capacity factor for wind versus nuclear) is at 2 dollars (in the newest, most efficient wind machines)and dropping.  With the mass production of 15,000 units the cost would drop signifigantly. And wind has no fuel or waste.  Cost of wind on that scale would be about 2 cents per kwh.

Half of national  electric power could come from home and commercial building installations of solar and over  parking lots, and the installation of small to medium wind systems.

The other half from these large wind machines.  Nuclear is just not necessary.  And it is far too expensive and dangerous.

That's all without even considering the waste, which could add up to a dollar ( or even more) per kwh generated over 10s of thousands of years of secure storage, not to mention transportation, processing, and  nuclear plant decommisioning.