Assume that the following electrical load, expressed in watts, requires the design and installation of a solar panel system with a yearly capacity of 4500 kWh or 4,500,000 Wh (12,330 Wh/day) with 400Wp PV modules.
| Load | Rated Power (W) | Hours/day | Product of rated power and Hours/day |
| Water pump | 900 | 2 | 1800 |
| Refrigerator | 80 | 5 | 400 |
| Electric frying pan | 500 | 2 | 1000 |
| 5 LED lamps (@10W each) | 50 | 10 | 500 |
| 5 Ceiling fans (@ 5W) | 25 | 5 | 125 |
| Electric iron | 700 | 1 | 700 |
| Washing machine | 500 | 2 | 1000 |
| Television | 100 | 8 | 800 |
| Laptop | 60 | 10 | 600 |
| Coffee maker | 200 | 2 | 400 |
| Dish washer | 700 | 3 | 2100 |
| Gas Heated | 400 | 2 | 800 |
| Air conditioner | 400 | 5 | 2000 |
| Total: | 4615 | 12,225 |
Total load is 12,225 Wh/day
- The required wattage by solar panels system
12,225 Wh x 1.3 = 15892.5 Wh/day
Note: 1.3 is a factor utilized for energy lost in the solar system
- The size of the solar panels
= 12.4 modules
The actual requirement of the panels is 12 modules
The system will be power by 12 modules of 400Wp PV modules
- Inverter size
The total required wattage for the appliances is 4615W
Due to inverter losses, the inverter’s rating now needs to be 25% higher than the overall load.
= 4615 x 2.5 = 11537.5 W
- Battery sizing
Total electrical appliances used = 12,225 Wh/day
Nominal battery voltage = 12V
Days of autonomy = 3 days
The battery should be rated 12V 1800 Ah for 3 days autonomy
- Solar charge controller sizing
PV module specification
Pm = 400 Wp
Vm = 30.7 Vdc
Im =13.03A
Voc = 40.7A
Isc = 15.5A
Solar charge controller rating = (12 strings x 7.5 A) x 1.3 = 117A
So we used 117A
- The series and parallel connection of modules
When solar cells are added in series, voltages are added. The current remains same. Power is product of voltage and current.
When solar cells are added in parallel, voltages remains same. The currents added. Power is product of voltage and current.
Five panels are connected in series while seven panels are connected in parallel.
VT = V1 + V2 + V3 …… = 30.7 x 5 =153.5V
IT = 13.03 X 7 = 91.21A
Power = VT x IT = 153.5 x 91.21 = 14,000.735 W = 14kW
