The core formula: appliance watts × hours = watt-hours (Wh). Your daily total Wh decides panel and battery size.
1. The four parts
| Part | Role |
|---|---|
| Solar panel | Turns sunlight into DC power |
| Charge controller | Protects the battery from overcharge and damage |
| Battery | Stores power for night and cloudy days |
| Inverter | Converts DC to AC for ordinary appliances |
2. A worked example
| Appliance | Watts | Hours/day | Wh |
|---|---|---|---|
| Fan | 60 | 6 | 360 |
| LED light | 10 | 5 | 50 |
| Phone charging, etc. | 10 | 3 | 30 |
| Total | 440 | ||
- Panel: 440 ÷ (4 sun hours × 0.7 efficiency) ≈ 157 W; in practice 160–200 W.
- Battery (12 V lead-acid): 440 ÷ (12 × 0.5) ≈ 73 Ah; for one day’s backup choose 100 Ah.
- If you use an inverter, add roughly 20% for losses.
3. Ways to save
- Choose LED lights and low-watt DC fans; leave heavy loads (heaters, fridges) off the first system.
- Face panels south at about 20–25° tilt; avoid shade.
- Wipe off dust occasionally.
4. Maintenance
- Keep batteries cool, dry and ventilated.
- Check wires and connections monthly.
Wiring and batteries can cause fire or electric shock. Have installation done by a qualified electrician.