...
Then, applications are categorized according to a household's system size. All systems lower than or equal to 10kW are considered small systems. Large Systems are further divided into 5 sub-categories, with values ranging from 10-2000kW. Below are the subcategories for households and buildings with a large system size:
>10-25kW
>25-100kW
>100-200kW
>200-500 kW
>500-2000 5000 kW
Blocks
Finally, the per megawatt rate is ultimately determined by the Block number. A specific system size is allocated for each block. The system size for the IL SREC is defined by the inverter size and is in W AC. More information on this can be found on the program FAQ. Once the system size is met based on the number of applications Illinois has received, they will close the current block and open a new block with a new and relatively lower rate.
...
Here's a table for reference (updated 12/14):
...
What makes IL SRECs special is they offer front loads, where you can be paid 85% of the 15-year SREC value upfront on year 1 for small systems, and up to 5-year SREC value for large systems.
Sighten calculates the value of the SRECs as: Total SRECs = System Inverter Capacity kW AC * 0.1642 / 1000 kW/MW * 8760 hours/year* 15 years. From the total number of SCREs, we multiply it by the SREC rate multiplied by the 15% discount.
...