Home Solar Calculator

Home Solar System Calculator

function calculateSolar() { var monthlyKwhUsage = parseFloat(document.getElementById('monthlyKwhUsage').value); var costPerKwh = parseFloat(document.getElementById('costPerKwh').value); var peakSunHours = parseFloat(document.getElementById('peakSunHours').value); var systemCostPerWatt = parseFloat(document.getElementById('systemCostPerWatt').value); var systemEfficiency = parseFloat(document.getElementById('systemEfficiency').value) / 100; // Convert to decimal var electricityInflation = parseFloat(document.getElementById('electricityInflation').value) / 100; // Convert to decimal var panelDegradation = parseFloat(document.getElementById('panelDegradation').value) / 100; // Convert to decimal // Input validation if (isNaN(monthlyKwhUsage) || monthlyKwhUsage <= 0 || isNaN(costPerKwh) || costPerKwh <= 0 || isNaN(peakSunHours) || peakSunHours <= 0 || isNaN(systemCostPerWatt) || systemCostPerWatt <= 0 || isNaN(systemEfficiency) || systemEfficiency 1 || isNaN(electricityInflation) || isNaN(panelDegradation)) { document.getElementById('solarResults').innerHTML = 'Please enter valid positive numbers for all fields.'; return; } // 1. Calculate Annual kWh Needed var annualKwhNeeded = monthlyKwhUsage * 12; // 2. Calculate Required System Size (kW) // Daily kWh needed = annualKwhNeeded / 365 // Required System Size (kW) = (Daily kWh needed / Peak Sun Hours) / System Efficiency var requiredSystemSizeKw = (annualKwhNeeded / 365 / peakSunHours) / systemEfficiency; var requiredSystemSizeWatts = requiredSystemSizeKw * 1000; // 3. Calculate Total System Cost var totalSystemCost = requiredSystemSizeWatts * systemCostPerWatt; // 4. Estimated Annual kWh Production (Year 1) var annualProductionKwhYear1 = requiredSystemSizeKw * peakSunHours * 365 * systemEfficiency; // 5. Estimated Annual Savings (Year 1) var annualSavingsYear1 = annualProductionKwhYear1 * costPerKwh; // 6. Simple Payback Period var simplePaybackPeriod = totalSystemCost / annualSavingsYear1; // 7. Projected 20-Year Savings (considering inflation and degradation) var cumulativeSavings = 0; var currentKwhCost = costPerKwh; var currentAnnualProduction = annualProductionKwhYear1; for (var year = 1; year 1) { currentAnnualProduction *= (1 – panelDegradation); } // Adjust electricity cost for inflation if (year > 1) { currentKwhCost *= (1 + electricityInflation); } cumulativeSavings += (currentAnnualProduction * currentKwhCost); } var net20YearSavings = cumulativeSavings – totalSystemCost; // Display Results var resultsHtml = '

Your Solar Potential Estimate:

'; resultsHtml += 'Required System Size: ' + requiredSystemSizeKw.toFixed(2) + ' kW'; resultsHtml += 'Estimated Total System Cost: $' + totalSystemCost.toFixed(2) + "; resultsHtml += 'Estimated Annual kWh Production (Year 1): ' + annualProductionKwhYear1.toFixed(0) + ' kWh'; resultsHtml += 'Estimated Annual Savings (Year 1): $' + annualSavingsYear1.toFixed(2) + "; resultsHtml += 'Simple Payback Period: ' + simplePaybackPeriod.toFixed(1) + ' years'; resultsHtml += 'Projected 20-Year Net Savings: $' + net20YearSavings.toFixed(2) + "; document.getElementById('solarResults').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: 600px; 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"] { width: calc(100% – 22px); padding: 12px; margin-bottom: 18px; 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 { border-color: #28a745; outline: none; box-shadow: 0 0 5px rgba(40, 167, 69, 0.3); } .calculator-inputs button { display: block; width: 100%; padding: 14px; background-color: #28a745; color: white; border: none; border-radius: 6px; font-size: 1.1em; font-weight: bold; cursor: pointer; transition: background-color 0.3s ease, transform 0.2s ease; margin-top: 20px; } .calculator-inputs button:hover { background-color: #218838; transform: translateY(-2px); } .calculator-inputs button:active { transform: translateY(0); } .calculator-results { margin-top: 30px; padding: 20px; background-color: #eaf7ed; border: 1px solid #d4edda; border-radius: 8px; color: #155724; } .calculator-results h3 { color: #28a745; margin-top: 0; margin-bottom: 15px; font-size: 1.5em; text-align: center; } .calculator-results p { margin-bottom: 10px; line-height: 1.6; font-size: 1.05em; } .calculator-results p strong { color: #155724; }

Understanding Your Home Solar Potential

Going solar is a significant investment that can lead to substantial long-term savings and environmental benefits. Our Home Solar System Calculator helps you estimate the size of the solar array you might need, its potential cost, and the financial returns you could expect over two decades.

How Solar Power Works for Your Home

Solar panels convert sunlight into direct current (DC) electricity. An inverter then changes this DC electricity into alternating current (AC) electricity, which is what your home appliances use. Any excess electricity your panels produce can often be sent back to the grid, potentially earning you credits through a process called net metering.

Key Factors in Solar System Sizing and Savings

Several variables influence how much solar power your home needs and how much you'll save:

  • Average Monthly Electricity Usage (kWh): This is the most crucial factor. Your past electricity bills will show your average monthly consumption in kilowatt-hours (kWh). The more electricity you use, the larger the solar system you'll need to offset it.
  • Average Electricity Cost per kWh ($): This figure, also found on your electricity bill, determines how much money you save for each kWh your solar system produces. Higher electricity rates mean greater savings.
  • Average Daily Peak Sun Hours: This refers to the average number of hours per day your solar panels receive direct, effective sunlight. It varies significantly by geographic location and season. Websites like the National Renewable Energy Laboratory (NREL) provide solar resource maps.
  • Estimated System Cost per Watt ($): This is the average cost to install solar panels, including equipment, labor, and permits, per watt of capacity. Prices vary based on location, system complexity, and installer.
  • System Efficiency Factor (%): Solar panels don't operate at 100% efficiency due to factors like temperature, shading, dust, and inverter losses. A typical efficiency factor ranges from 75% to 85%.
  • Annual Electricity Price Increase (%): Electricity prices tend to rise over time. Factoring in an annual increase helps project more realistic long-term savings.
  • Annual Panel Degradation (%): Solar panels gradually lose a small amount of their efficiency each year. Most quality panels degrade by about 0.5% to 1% annually.

Interpreting Your Calculator Results

  • Required System Size (kW): This is the estimated capacity of the solar system needed to cover your current electricity usage. For example, a 7 kW system might be suitable for a home with average consumption.
  • Estimated Total System Cost: This is a rough estimate of the upfront investment required for your solar system before any incentives or tax credits.
  • Estimated Annual kWh Production (Year 1): This shows how much electricity your system is expected to generate in its first year.
  • Estimated Annual Savings (Year 1): This is the monetary value of the electricity your system produces in its first year, based on your current electricity cost.
  • Simple Payback Period: This indicates how many years it will take for your annual savings to equal your initial investment, without considering inflation or degradation.
  • Projected 20-Year Net Savings: This is a more comprehensive estimate of your total financial benefit over two decades, accounting for rising electricity prices and panel degradation. It subtracts the initial system cost from the cumulative savings.

Important Considerations

This calculator provides an estimate. For a precise assessment, it's crucial to get quotes from local solar installers. They can evaluate your specific roof characteristics, shading, local regulations, and available incentives (like federal tax credits, state rebates, or local programs) which can significantly impact your final cost and payback period.

Remember that solar technology is constantly evolving, and prices can fluctuate. Always consult with certified professionals for a detailed home solar energy plan.

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