Methods for determining a budget can be based on square footage of space available, percentage of usage you want to offset or amount you want to spend or finance.
System pricing is typically based on dollars per watt ($/W) of installed capacity, with small commercial systems sized 10 – 100 kW, and large systems starting at 100 kW .
Small commercial and residential system pricing – before incentives – can range from $3.00 to $4.00 per watt. The price range will vary depending on the system size, the desired power density, type of equipment, the site conditions and other variables.
Once you have determined an approximate size of the system in kilowatts (kW), you can multiply by the range above to get an idea of what it would cost.
Use the following rule to determine the approximate system size that your roof can accommodate:
1 kW = 100 square feet of roof space (clear space)
You can determine the energy output of your system by multiplying the installed capacity in kilowatts by 1200 (sun-hours per year) –
System Size (kW) X 1200 (Sun hours per year) = kWh per year
This number can help give an idea of what size system would be needed to achieve certain offset goals.