Off Grid Solar Calculator

Off-Grid Solar System Calculator

Total energy used by all appliances in a day.

Average hours per day your location receives direct sunlight equivalent to 1000 W/m².

12V 24V 48V

Common system voltages for off-grid setups.

How many days the system can run without sun (e.g., during cloudy weather).

Maximum percentage of battery capacity used to prolong battery life (e.g., 50% for lead-acid, 80-90% for LiFePO4).

Efficiency of your inverter in converting DC to AC power.

Losses due to wiring, temperature, dust, and other factors.

Estimated Costs (Optional for calculation, but recommended for total cost)

Average cost per watt for solar panels ($).

Average cost per usable kilowatt-hour of battery storage ($).

Cost of the inverter unit ($).

Cost of the charge controller unit ($).

Estimated costs for mounting, wiring, labor, and other components ($).

function calculateSolarSystem() { var dailyEnergyConsumption = parseFloat(document.getElementById('dailyEnergyConsumption').value); var peakSunHours = parseFloat(document.getElementById('peakSunHours').value); var systemVoltage = parseFloat(document.getElementById('systemVoltage').value); var daysAutonomy = parseFloat(document.getElementById('daysAutonomy').value); var batteryDoD = parseFloat(document.getElementById('batteryDoD').value); var inverterEfficiency = parseFloat(document.getElementById('inverterEfficiency').value); var systemLosses = parseFloat(document.getElementById('systemLosses').value); var panelCostPerWatt = parseFloat(document.getElementById('panelCostPerWatt').value); var batteryCostPerUsableKWh = parseFloat(document.getElementById('batteryCostPerUsableKWh').value); var inverterCost = parseFloat(document.getElementById('inverterCost').value); var chargeControllerCost = parseFloat(document.getElementById('chargeControllerCost').value); var installationCost = parseFloat(document.getElementById('installationCost').value); var resultDiv = document.getElementById('result'); resultDiv.innerHTML = "; // Clear previous results // Input validation if (isNaN(dailyEnergyConsumption) || dailyEnergyConsumption <= 0 || isNaN(peakSunHours) || peakSunHours <= 0 || isNaN(systemVoltage) || systemVoltage <= 0 || isNaN(daysAutonomy) || daysAutonomy <= 0 || isNaN(batteryDoD) || batteryDoD 100 || isNaN(inverterEfficiency) || inverterEfficiency 100 || isNaN(systemLosses) || systemLosses = 100) { resultDiv.innerHTML = 'Please enter valid positive numbers for all primary inputs. Battery DoD, Inverter Efficiency, and System Losses should be between 0 and 100.'; return; } // Convert percentages to decimals var inverterEfficiencyFactor = inverterEfficiency / 100; var batteryDoDFactor = batteryDoD / 100; var systemLossesFactor = systemLosses / 100; // 1. Adjusted Daily Energy Demand (Wh) – accounts for inverter losses var adjustedDailyEnergyDemand = dailyEnergyConsumption / inverterEfficiencyFactor; // 2. Required Solar Panel Array Size (Watts) – accounts for system losses var requiredSolarPanelArraySize = (adjustedDailyEnergyDemand / peakSunHours) / (1 – systemLossesFactor); // 3. Required Battery Bank Capacity (Wh and kWh) var requiredBatteryBankCapacityWh = adjustedDailyEnergyDemand * daysAutonomy; var requiredUsableBatteryCapacityWh = requiredBatteryBankCapacityWh / batteryDoDFactor; var requiredUsableBatteryCapacityKWh = requiredUsableBatteryCapacityWh / 1000; // 4. Required Battery Bank Capacity (Ah at system voltage) var requiredBatteryBankCapacityAh = requiredUsableBatteryCapacityWh / systemVoltage; // 5. Estimated Total System Cost var totalEstimatedCost = 0; var panelCost = 0; var batteryCost = 0; if (!isNaN(panelCostPerWatt) && panelCostPerWatt >= 0) { panelCost = requiredSolarPanelArraySize * panelCostPerWatt; totalEstimatedCost += panelCost; } if (!isNaN(batteryCostPerUsableKWh) && batteryCostPerUsableKWh >= 0) { batteryCost = requiredUsableBatteryCapacityKWh * batteryCostPerUsableKWh; totalEstimatedCost += batteryCost; } if (!isNaN(inverterCost) && inverterCost >= 0) { totalEstimatedCost += inverterCost; } if (!isNaN(chargeControllerCost) && chargeControllerCost >= 0) { totalEstimatedCost += chargeControllerCost; } if (!isNaN(installationCost) && installationCost >= 0) { totalEstimatedCost += installationCost; } // Display results var resultsHtml = '

Calculation Results:

'; resultsHtml += 'Required Solar Panel Array Size: ' + requiredSolarPanelArraySize.toFixed(2) + ' Watts'; resultsHtml += 'Required Usable Battery Capacity: ' + requiredUsableBatteryCapacityKWh.toFixed(2) + ' kWh'; resultsHtml += 'Required Battery Bank Capacity: ' + requiredBatteryBankCapacityAh.toFixed(2) + ' Ah (at ' + systemVoltage + 'V)'; if (panelCostPerWatt >= 0 || batteryCostPerUsableKWh >= 0 || inverterCost >= 0 || chargeControllerCost >= 0 || installationCost >= 0) { resultsHtml += 'Estimated Total System Cost: $' + totalEstimatedCost.toFixed(2) + "; resultsHtml += '(Panel Cost: $' + panelCost.toFixed(2) + ', Battery Cost: $' + batteryCost.toFixed(2) + ', Inverter Cost: $' + inverterCost.toFixed(2) + ', Charge Controller Cost: $' + chargeControllerCost.toFixed(2) + ', Installation Cost: $' + installationCost.toFixed(2) + ')'; } else { resultsHtml += 'Cost estimation skipped due to missing or invalid cost inputs.'; } resultDiv.innerHTML = resultsHtml; } .calculator-container { font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif; background-color: #f9f9f9; padding: 25px; border-radius: 10px; box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1); max-width: 700px; margin: 30px auto; border: 1px solid #e0e0e0; } .calculator-container h2 { text-align: center; color: #2c3e50; margin-bottom: 25px; font-size: 1.8em; } .calculator-inputs label { display: block; margin-bottom: 8px; color: #34495e; font-weight: bold; font-size: 0.95em; } .calculator-inputs input[type="number"], .calculator-inputs select { width: calc(100% – 22px); padding: 12px; margin-bottom: 10px; border: 1px solid #ccc; border-radius: 6px; font-size: 1em; box-sizing: border-box; transition: border-color 0.3s ease; } .calculator-inputs input[type="number"]:focus, .calculator-inputs select:focus { border-color: #3498db; outline: none; } .calculator-inputs .input-description { font-size: 0.85em; color: #7f8c8d; margin-top: -5px; margin-bottom: 15px; padding-left: 5px; } .calculator-inputs h3 { color: #2c3e50; margin-top: 30px; margin-bottom: 15px; border-bottom: 1px solid #eee; padding-bottom: 5px; font-size: 1.3em; } .calculator-inputs button { display: block; width: 100%; padding: 15px; background-color: #28a745; color: white; border: none; border-radius: 6px; font-size: 1.1em; font-weight: bold; cursor: pointer; margin-top: 25px; transition: background-color 0.3s ease, transform 0.2s ease; } .calculator-inputs button:hover { background-color: #218838; transform: translateY(-2px); } .calculator-results { margin-top: 30px; padding: 20px; background-color: #e8f5e9; border: 1px solid #c8e6c9; border-radius: 8px; color: #2c3e50; } .calculator-results h3 { color: #1b5e20; margin-top: 0; margin-bottom: 15px; font-size: 1.5em; } .calculator-results p { margin-bottom: 10px; line-height: 1.6; font-size: 1em; } .calculator-results p strong { color: #333; } .calculator-results .cost-breakdown { font-size: 0.9em; color: #555; margin-top: 5px; }

Understanding Your Off-Grid Solar System Needs

Going off-grid means achieving energy independence, relying solely on your own power generation and storage, typically from solar panels. This calculator helps you estimate the key components and potential costs for setting up a robust off-grid solar system tailored to your specific energy demands and location.

What is an Off-Grid Solar System?

Unlike grid-tied solar systems that remain connected to the utility grid, an off-grid system operates completely independently. It's ideal for remote properties, cabins, or anyone seeking complete energy self-sufficiency. The core components include:

  • Solar Panels: Convert sunlight into DC electricity.
  • Charge Controller: Regulates the voltage and current from the solar panels to the batteries, preventing overcharging.
  • Battery Bank: Stores excess energy generated by the panels for use when the sun isn't shining (e.g., at night or on cloudy days).
  • Inverter: Converts the DC electricity stored in the batteries into AC electricity, which is what most household appliances use.

Key Inputs Explained:

To get an accurate estimate, understanding each input is crucial:

  • Daily Energy Consumption (Wh): This is the most critical input. It represents the total amount of energy your household or property uses in a typical day. You can estimate this by listing all your appliances, their wattage, and how many hours per day they run. For example, a 100W light bulb running for 5 hours uses 500 Wh (100W * 5h).
  • Average Peak Sun Hours (hours): This refers to the average number of hours per day your location receives sunlight intense enough to generate the rated power of your solar panels. This value varies significantly by geographic location and season. You can find this data from solar maps or local weather resources.
  • System Voltage (V): Common off-grid system voltages are 12V, 24V, and 48V. Higher voltages are generally more efficient for larger systems as they reduce current and wiring losses.
  • Days of Autonomy (days): This is how many days your battery bank can power your home without any solar input (e.g., during extended cloudy periods). A higher number provides more resilience but increases battery costs.
  • Battery Depth of Discharge (DoD %): This is the maximum percentage of your battery's capacity you plan to use before recharging. Discharging batteries too deeply can significantly shorten their lifespan. For lead-acid batteries, 50% DoD is common, while lithium iron phosphate (LiFePO4) batteries can often handle 80-90% DoD.
  • Inverter Efficiency (%): Inverters are not 100% efficient; some energy is lost during the DC to AC conversion. Typical efficiencies range from 85% to 95%.
  • System Losses (%): This accounts for various inefficiencies in the entire system, including wiring resistance, temperature effects on panels, dust accumulation, and minor component losses. A common range is 15-25%.

Understanding the Results:

The calculator provides estimates for the following:

  • Required Solar Panel Array Size (Watts): The total wattage of solar panels you'll need to generate enough electricity to meet your daily demand, considering sun hours and system losses.
  • Required Usable Battery Capacity (kWh): The total amount of energy your battery bank needs to store to cover your autonomy days, taking into account your desired Depth of Discharge.
  • Required Battery Bank Capacity (Ah at system voltage): The Amp-hour rating of your battery bank at your chosen system voltage, which helps in selecting specific battery units.
  • Estimated Total System Cost ($): A rough estimate of the overall investment, including panels, batteries, inverter, charge controller, and installation. Remember that these are estimates, and actual costs can vary based on brands, installation complexity, and market fluctuations.

Important Considerations:

This calculator provides a valuable starting point, but a professional solar installer can offer a precise design and quote based on a detailed site assessment. Factors like shading, roof orientation, local regulations, and specific appliance surge requirements can influence the final system design. Always consult with experts before making significant investments.

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