Solar panels convert sunlight into DC electricity.The inverter converts DC into AC electricity.Electricity powers household appliances.Excess electricity can be exported to the grid if permitted.A standard On-Grid system usually shuts down during a power cut for safety.Advantages: Lower electricity bills, no battery required in a typical system, and lower maintenance costs.2. Off-Grid Solar SystemOff grid solar power system: energy freedom, savingsbr-solar.comAn Off-Grid Solar System works independently of the electricity grid.Working:Solar panels generate DC electricity.The charge controller regulates battery charging.The battery stores electrical energy.The inverter converts DC into AC electricity.Stored energy can power appliances at night or during a power cut.Advantages: Independent power supply, battery backup, and suitability for remote areas.3. Solar Calculator FormulasA. Daily energy consumption\[ E=\frac{P\times T}{1000} \]\(E\) = Energy consumption (kWh or units)\(P\) = Appliance power (watts)\(T\) = Usage time (hours)B. Required solar panel capacity\[ \text{Solar Capacity (kW)} =\frac{\text{Daily Energy (kWh)}}{\text{Sunlight Hours}\times\text{Efficiency Factor}} \]Use approximately 0.75 as a preliminary efficiency factor.Example:Daily energy consumption = 6 kWhEffective sunlight = 5 hours/day\[ =\frac{6}{5\times0.75}=1.6\text{ kW} \]Therefore, the estimated solar capacity is 1.6 kW. A practical system size must be selected after checking site conditions and actual loads.C. Number of solar panels\[ \text{Number of Panels} =\frac{\text{Required Capacity (W)}}{\text{Panel Rating (W)}} \]Example: For a 2,000 W system using 500 W panels:\[ =\frac{2000}{500}=\boxed{4\text{ panels}} \]D. Battery capacity for an Off-Grid system\[ \text{Battery Capacity (Wh)} =\frac{\text{Daily Energy (Wh)}\times\text{Backup Days}}{\text{Usable Battery Fraction}\times\text{Inverter Efficiency}} \]Example: Daily backup energy = 2,000 Wh, backup = 1 day, usable battery fraction = 0.8, inverter efficiency = 0.9.\[ =\frac{2000\times1}{0.8\times0.9} \approx2778\text{ Wh} \]Estimated battery capacity = 2.78 kWh.4. Main DifferencesFeature On-Grid Off-GridGrid connection Required Not requiredBattery Usually not required RequiredPower during outages Usually unavailable Available if battery has chargeInitial cost Generally lower Generally higherMain use Homes connected to the grid Remote locations or independent powerConclusion: On-Grid systems help reduce electricity bills, while Off-Grid systems provide independent electricity using battery storage. Always consult a qualified solar installer for the final system design.
