The document summarizes the system calculations for sizing a solar photovoltaic system to offset 100% of a customer's energy usage of 6,000 KWh per year or 16.44 KWh per day. Based on the site specifications and module characteristics, the calculations determine that a 3.97 KW system with a maximum of 11 and minimum of 6 modules per string is needed, and that #10 gauge wires can be used for the DC and AC sides of the system within safety limits.

1. System Calculations
SystemSizing:
Customerwantsto offset100 percentof energyusage:
Annual EnergyUsage = 6,000 KWh/ 365 days= 16.44 KWh per day
16.44 KWhper day / 5.35 PeakSunHours / .9 (STCto PTC) / .86 (DC to AC) = 3.97 Kw systemneeded
MaximumNumberof ModulesperString:
Ashrae Extreme Min.Temp.= -23°C - 25 = -48 x -.33 (Temp.Coefficientof Vocperdegree) = 15.84% x
38.4V = 6.08V
Module Voc= 38.4V + 6.08V = 44.48V (Temp.CorrectedVoc)
500V (InverterVmax Input) /44.48V = 11.24  (RoundDown) 11 MaximumPanelsperString
MaximumPanels=11 > 8 Panelsperstring OK
MinimumNumberof ModulesperString:
Ashrae Extreme Max.Temp.= 56°C – 25 = 31 x -.45 (Temp.Cofficientof Vmppperdegree)=13.95% x
30.4V (Vmpof Module) =4.24V
Module Vmp= 30.4V – 4.24v = 26.16V (Temp.CorrectedVmp)
150V (InverterVminInput)/26.16V = 5.73  (RoundUp) 6 MinimumPanelsperString
MinimumPanels=6 < 8 Panelsperstring OK
DC Side:
Array to Combiner
Module ISC= 8.79A x 1.25 (ContinuousUse) x 1.25 (Irradiance overSTC) = 13.73A
#12AWG PV wire ampacity= 30A > 13.73A  so itis okto use
CombinertoInverter
Module ISC= 8.79A x 1.25 (ContinuousUse) x 1.25 (Irradiance overSTC) x 2 (Stringsinparallel) =27.47A
#10AWG THWN ampacity= 40A > 27.47A  so it isok to use
DC OCPD: 8.79A x 1.25 x 1.25 x 2 = 27.47A  30A Breakeron DC Disconnect
AC Side:
InvertertoMain Panel
InverterOutputPower=4000 watts / 240V = 16.667A x 1.25 = 20.83A
#10AWG THWN wire ampacity= 40A  20.83A so it isok to use

2. AC OCPD:4000w /240v x 1.25 = 20.83A  25A breakeronAC Disconnect
EGC Calculation:
OCPDdoesn’texceed60A  #10AWG Copperisok
GEC Calculation:
LargestOCPD is30A  #6AWG Copperisok
Main Panel:
Main Panel isratedfor 200A with160A used
200A x 120% = 240A available –160A used= 80A available space
20.83A < 80A  OK to connectto mainpanel busbar