The duty cycle for intermittent renewable resources of wind and solar is not operator controlled, but dependent on the weather or solar cycle (that is, sunrise/sunset). The availability of wind or solar will not necessarily correspond to operator dispatched duty cycles and, as a result, their levelized costs are not directly comparable to those for other technologies (even where the average annual capacity factor may be similar). In addition, intermittent technologies do not provide the same contribution to system reliability as dispatched resources, and may require additional system investment (not shown) to achieve a desired level of reliability.These investments would include large scale expansion of grid long range transmission infrastructure, energy storage facilities or natural gas fired generators, and redundant renewable generating capacity. Thus the levelized cost of solar and wind do not reflect the entire cost of generating electricity using renewable sources. Eastern Wind Integration and Transmission Study(EWITS) estimated that a 20% onshore wind penetration of the Eastern Interconnect would require a $93 billion grid expansion.
That report found that the annualized cost of electricity from a 20% penetrated grid would be about 10% higher than the low wind reference case. The EWITS also found that without the grid long distance transmission expansion, grid expenses would be even higher. Finally the study suggested that an aggressive attempt to expand the wind penetration to 30% which included the use of offshore wind, would increase grid annualized cost by nearly 30% above the reference case. Thus a greater grid penetration by wind lead to higher electrical costs. The added annualized cost for greater wind penetration occurred despite a considerable decline in fuel related costs associated with greater wind penetration.
The EIA estimates the total levelized cost of the common post-carbon electrical options to be,
Onshore Wind 149.3
Offshore Wind 191.1
Solar PV 396.1
Solar Thermal 256.6
Advanced Nuclear 119.0