This optional column defines the cold start period for a unit and should be entered as an integer value larger than the Start Up Hours Warm value. When a unit has been down this many hours exactly and starts up again, the start cost amount is defined by the Start Up Costs and Start Fuel Amount columns.

Note that if the unit has been down for a number of hours between the Start Up Hours Hot and the Start Up Hours Warm or between Start Up Hours Warm and Start Up Hours Cold, Aurora will do a linear interpolation between the two corresponding costs to figure out the cost to start at that hour.  

For example, if the total warm start up cost is $10,000, the total cold start up cost is $20,000, the Start Up Hours Warm is 20, the Start Up Hours Cold is 40, and the unit start up after 30 hours, the cost will be $15,000.