Solar Panel System Calculator

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Solar Panel System Calculator

Use this calculator to estimate the size of the solar panel system you'll need, the number of panels, and the approximate cost based on your energy consumption and local conditions.

Enter your average daily electricity usage in kilowatt-hours (kWh). You can find this on your electricity bill.

This is the equivalent number of hours per day when solar irradiance averages 1,000 watts per square meter. It varies by location and time of year. A common range is 3-6 hours.

Accounts for real-world losses from inverter efficiency, wiring, temperature, and dirt. A typical range is 75-85%.

The power output of a single solar panel. Common residential panels range from 300W to 450W.

The percentage of your daily energy consumption you want your solar system to cover. Enter 100 for full coverage.

The average cost per watt for a fully installed residential solar system. This can vary significantly by region, installer, and system size. (e.g., $2.50 – $4.00)

Calculation Results:

Enter values and click "Calculate System" to see your results.

function calculateSolarSystem() { var dailyEnergyConsumption = parseFloat(document.getElementById('dailyEnergyConsumption').value); var peakSunHours = parseFloat(document.getElementById('peakSunHours').value); var systemEfficiency = parseFloat(document.getElementById('systemEfficiency').value); var panelWattage = parseFloat(document.getElementById('panelWattage').value); var desiredCoverage = parseFloat(document.getElementById('desiredCoverage').value); var costPerWatt = parseFloat(document.getElementById('costPerWatt').value); var resultDiv = document.getElementById('result'); resultDiv.innerHTML = "; // Clear previous results // Input validation if (isNaN(dailyEnergyConsumption) || dailyEnergyConsumption <= 0) { resultDiv.innerHTML = 'Please enter a valid positive number for Average Daily Energy Consumption.'; return; } if (isNaN(peakSunHours) || peakSunHours <= 0) { resultDiv.innerHTML = 'Please enter a valid positive number for Average Daily Peak Sun Hours.'; return; } if (isNaN(systemEfficiency) || systemEfficiency 100) { resultDiv.innerHTML = 'Please enter a valid System Efficiency Factor between 1 and 100.'; return; } if (isNaN(panelWattage) || panelWattage <= 0) { resultDiv.innerHTML = 'Please enter a valid positive number for Individual Solar Panel Wattage.'; return; } if (isNaN(desiredCoverage) || desiredCoverage 100) { resultDiv.innerHTML = 'Please enter a valid Desired Energy Coverage between 1 and 100.'; return; } if (isNaN(costPerWatt) || costPerWatt <= 0) { resultDiv.innerHTML = 'Please enter a valid positive number for Estimated System Cost per Watt.'; return; } // Convert percentages to decimals var efficiencyFactor = systemEfficiency / 100; var coverageFactor = desiredCoverage / 100; // 1. Calculate Target Daily Energy Production (kWh) var targetDailyProduction = dailyEnergyConsumption * coverageFactor; // 2. Calculate Required DC System Size (kW) // Formula: (Target Daily Production / Peak Sun Hours) / Efficiency Factor // This gives the AC output needed, then we divide by efficiency to get the DC input required from panels. var requiredDCSystemSizeKW = (targetDailyProduction / peakSunHours) / efficiencyFactor; // 3. Calculate Number of Panels // Convert kW to Watts for panel calculation: requiredDCSystemSizeKW * 1000 var numberOfPanels = Math.ceil((requiredDCSystemSizeKW * 1000) / panelWattage); // 4. Calculate Estimated Total System Cost ($) var estimatedTotalCost = requiredDCSystemSizeKW * 1000 * costPerWatt; // Display results resultDiv.innerHTML += 'Target Daily Energy Production: ' + targetDailyProduction.toFixed(2) + ' kWh'; resultDiv.innerHTML += 'Required DC System Size: ' + requiredDCSystemSizeKW.toFixed(2) + ' kW'; resultDiv.innerHTML += 'Estimated Number of Panels: ' + numberOfPanels + ' panels'; resultDiv.innerHTML += 'Estimated Total System Cost: $' + estimatedTotalCost.toFixed(2).replace(/\B(?=(\d{3})+(?!\d))/g, ",") + "; resultDiv.innerHTML += 'Note: This is an estimate. Actual costs and system performance may vary based on installation specifics, incentives, and local regulations.'; } .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 { color: #2c3e50; text-align: center; margin-bottom: 20px; font-size: 28px; } .calculator-container p { color: #555; line-height: 1.6; margin-bottom: 15px; } .calc-input-group { margin-bottom: 18px; padding: 10px; background-color: #ffffff; border-radius: 8px; border: 1px solid #e9ecef; } .calc-input-group label { display: block; margin-bottom: 8px; color: #34495e; font-weight: bold; font-size: 16px; } .calc-input-group input[type="number"] { width: calc(100% – 20px); padding: 12px; border: 1px solid #ccc; border-radius: 6px; font-size: 16px; box-sizing: border-box; transition: border-color 0.3s ease; } .calc-input-group input[type="number"]:focus { border-color: #007bff; outline: none; box-shadow: 0 0 0 3px rgba(0, 123, 255, 0.25); } .input-help { font-size: 13px; color: #777; margin-top: 8px; padding-left: 5px; } .calculator-container button { display: block; width: 100%; padding: 15px; background-color: #28a745; color: white; border: none; border-radius: 6px; font-size: 18px; font-weight: bold; cursor: pointer; transition: background-color 0.3s ease, transform 0.2s ease; margin-top: 25px; } .calculator-container button:hover { background-color: #218838; transform: translateY(-2px); } .calculator-container button:active { transform: translateY(0); } .calc-results { margin-top: 30px; padding: 20px; background-color: #eaf7ed; border: 1px solid #d4edda; border-radius: 10px; box-shadow: 0 2px 8px rgba(0, 0, 0, 0.08); } .calc-results h3 { color: #28a745; margin-top: 0; margin-bottom: 15px; font-size: 22px; text-align: center; } .calc-results p { font-size: 17px; color: #333; margin-bottom: 10px; } .calc-results p strong { color: #2c3e50; }

Understanding Your Solar Panel System Needs

Going solar is a significant investment that promises long-term savings and environmental benefits. However, determining the right size and cost of a solar panel system for your home can be complex. Our Solar Panel System Calculator simplifies this process by providing an estimate based on your specific energy consumption and local conditions.

How the Calculator Works

This tool uses several key inputs to provide a realistic estimate of your solar system requirements:

Average Daily Energy Consumption (kWh)

This is the most crucial factor. Your electricity bill will typically show your monthly or daily energy usage in kilowatt-hours (kWh). The more energy you consume, the larger the solar system you'll need to offset that consumption. For example, a household using 30 kWh per day will require a larger system than one using 15 kWh per day.

Average Daily Peak Sun Hours (hours)

Peak sun hours represent the intensity of sunlight your location receives throughout the day, averaged over a year. It's not just the number of hours the sun is out, but how many hours the sun is strong enough to generate significant power. This value varies significantly by geographic location, season, and even local shading. For instance, a sunny state like Arizona might have 5-6 peak sun hours, while a cloudier region might have 3-4. This directly impacts how much energy your panels can produce daily.

System Efficiency Factor (%)

No solar system operates at 100% efficiency. This factor accounts for various real-world losses, including:

  • Inverter Efficiency: Converts DC power from panels to AC power for your home.
  • Wiring Losses: Some energy is lost as heat in the electrical wiring.
  • Temperature Losses: Solar panels become less efficient as their temperature increases.
  • Dirt and Dust: Accumulation on panels reduces sunlight absorption.
  • Shading: Even partial shading can significantly reduce output.

A typical residential system efficiency factor ranges from 75% to 85%. Our calculator uses a default of 80%.

Individual Solar Panel Wattage (W)

This refers to the power output of a single solar panel under standard test conditions. Residential solar panels commonly range from 300 watts (W) to 450W. Higher wattage panels can mean fewer panels are needed for the same system size, potentially saving roof space and installation time.

Desired Energy Coverage (%)

You might not want to cover 100% of your energy needs with solar, especially if you have net metering policies that aren't favorable for overproduction, or if you're working with a limited budget or roof space. This input allows you to specify what percentage of your daily consumption you aim to offset with solar power.

Estimated System Cost per Watt ($/W)

The total cost of a solar system is often quoted as a price per watt. This includes the cost of panels, inverters, mounting hardware, labor, permits, and other miscellaneous expenses. This value can vary widely based on your location, the installer, the quality of components, and the overall system size. For example, a smaller system might have a higher cost per watt than a larger one due to fixed installation costs. Typical residential costs range from $2.50 to $4.00 per watt before incentives.

Understanding the Results

  • Target Daily Energy Production: This is the amount of energy (in kWh) your solar system needs to generate daily to meet your desired coverage.
  • Required DC System Size (kW): This is the total power output (in kilowatts) your solar panels need to produce under ideal conditions to meet your target daily production, accounting for system losses.
  • Estimated Number of Panels: Based on the required system size and the wattage of individual panels, this tells you approximately how many panels you'll need. This number is rounded up to ensure full coverage.
  • Estimated Total System Cost: This provides a rough estimate of the total upfront cost of your solar system before any tax credits, rebates, or incentives.

Important Considerations

While this calculator provides a solid starting point, remember that it offers an estimate. For a precise quote and system design, you should consult with professional solar installers. They can assess your specific roof characteristics, shading issues, local building codes, and available incentives (like federal tax credits or state rebates) to provide a tailored solution.

Factors not included in this calculator but crucial for a complete assessment:

  • Local Incentives: Federal tax credits, state rebates, and local programs can significantly reduce the net cost.
  • Battery Storage: If you want to store excess energy for use at night or during power outages, this will add to the cost.
  • Roof Condition: The age and condition of your roof might require repairs or replacement before solar installation.
  • Shading Analysis: Professional installers perform detailed shading analysis to optimize panel placement.

By using this calculator, you can gain a better understanding of the potential scope and cost of your solar energy project, empowering you to make informed decisions on your path to energy independence.

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