CSLB C-46 Solar ContractorPlanning and EstimatingMedium
A solar contractor is planning a grid-tied residential PV system. The client's average daily energy consumption is 25 kWh. The site receives an effective 5.5 sun-hours per day, and the system's derate factor is estimated to be 0.75. What is the minimum DC array size (in kW) required to meet 100% of the client's energy needs?
- A4.55 kW
- B8.08 kW
- C6.06 kW
- D10.77 kW
Show answer & explanationAnswer & explanation
Correct answer: C. 6.06 kW
To meet 100% of the client's energy needs, the required daily AC production is 25 kWh. This production is achieved by dividing the daily AC production by the product of sun-hours and the derate factor (25 kWh / (5.5 sun-hours * 0.75)) to get the required DC array size.
Why the other options are wrong
- A. This calculation incorrectly divides by the derate factor twice or uses an incorrect sun-hour value.
- B. This calculation likely omits the derate factor or misapplies it.
- D. This calculation likely divides by sun-hours only, without considering the derate factor.
PV System Sizing (DC Array)
Determining the necessary DC array capacity to meet a specific energy demand, considering site-specific solar irradiance and system inefficiencies.
- Depends on average daily energy consumption.
- Requires effective sun-hours (insolation).
- Includes a derate factor for system losses.
Memory trick: Sun's power, client's need, system's loss – size it right, no energy toss!