Solar Size Calculator

Solar Panel System Size Calculator

Estimate the ideal solar panel system size for your home or business based on your energy consumption and local sunlight conditions.

(e.g., from your electricity bill)

(Varies by location and season. Use an average for your area.)

(Accounts for inefficiencies like wiring, inverter, temperature. Typical: 15-25%)

(Typical residential panels are 300-450W)

function calculateSolarSize() { var dailyKWH = parseFloat(document.getElementById('dailyKWH').value); var peakSunHours = parseFloat(document.getElementById('peakSunHours').value); var systemLoss = parseFloat(document.getElementById('systemLoss').value); var panelWattage = parseFloat(document.getElementById('panelWattage').value); var solarResultDiv = document.getElementById('solarResult'); if (isNaN(dailyKWH) || dailyKWH <= 0) { solarResultDiv.innerHTML = 'Please enter a valid positive number for Average Daily Energy Consumption.'; solarResultDiv.style.display = 'block'; return; } if (isNaN(peakSunHours) || peakSunHours <= 0) { solarResultDiv.innerHTML = 'Please enter a valid positive number for Average Peak Sun Hours.'; solarResultDiv.style.display = 'block'; return; } if (isNaN(systemLoss) || systemLoss = 100) { solarResultDiv.innerHTML = 'Please enter a valid System Loss Factor between 0 and 99.'; solarResultDiv.style.display = 'block'; return; } if (isNaN(panelWattage) || panelWattage <= 0) { solarResultDiv.innerHTML = 'Please enter a valid positive number for Individual Solar Panel Wattage.'; solarResultDiv.style.display = 'block'; return; } // Convert daily kWh to daily Wh var dailyEnergyWh = dailyKWH * 1000; // Calculate the efficiency factor (1 – loss percentage) var efficiencyFactor = 1 – (systemLoss / 100); // Calculate the required system output in Watts // Formula: (Daily Energy Wh / Peak Sun Hours) / Efficiency Factor var requiredSystemOutputW = (dailyEnergyWh / peakSunHours) / efficiencyFactor; // Convert to kW var requiredSystemOutputKW = requiredSystemOutputW / 1000; // Calculate the estimated number of panels var numberOfPanels = Math.ceil(requiredSystemOutputW / panelWattage); var resultHTML = '

Your Estimated Solar System Needs:

'; resultHTML += 'Required System Size: ' + requiredSystemOutputKW.toFixed(2) + ' kW (' + requiredSystemOutputW.toFixed(0) + ' W)'; resultHTML += 'Estimated Number of Panels: ' + numberOfPanels + ' panels (assuming ' + panelWattage + 'W per panel)'; resultHTML += 'This is an estimate. Actual requirements may vary based on specific site conditions, future energy needs, and panel degradation.'; solarResultDiv.innerHTML = resultHTML; solarResultDiv.style.display = 'block'; }

Understanding Your Solar Panel System Size

Determining the correct size for your solar panel system is the first critical step towards energy independence and savings. An accurately sized system ensures you generate enough electricity to meet your household's demands without over-investing in unnecessary capacity. This calculator helps you estimate the total wattage (W) or kilowattage (kW) your solar array should produce.

Key Factors in Solar Sizing:

• Average Daily Energy Consumption (kWh): This is the most crucial input. It represents how much electricity your home uses on an average day. You can typically find this information on your monthly electricity bills, often listed as "kWh used" or "average daily usage." The more energy you consume, the larger your solar system will need to be.
• Average Peak Sun Hours per Day (hours): Also known as "full sun hours," this refers to the number of hours per day when the intensity of sunlight averages 1,000 watts per square meter. This value varies significantly by geographic location, season, and local weather patterns. Online resources or local solar installers can provide accurate peak sun hour data for your specific area. More peak sun hours mean you can generate the same amount of energy with a smaller system.
• System Loss Factor (%): No solar system operates at 100% efficiency. Various factors contribute to energy loss, including wiring resistance, inverter efficiency, temperature effects on panels, dust/dirt accumulation, and shading. A typical loss factor ranges from 15% to 25%. This calculator uses this factor to ensure the system is sized to compensate for these inevitable losses.
• Individual Solar Panel Wattage (W): This refers to the power output of a single solar panel under standard test conditions. Residential panels commonly range from 300W to 450W. Knowing this helps translate the total required system wattage into an estimated number of physical panels you'll need.

How the Calculation Works:

The calculator first determines your total daily energy need in Watt-hours (Wh) by converting your kWh input. It then divides this by your average peak sun hours to find the raw power output required. Finally, it adjusts this figure upwards by accounting for the system loss factor, ensuring the system is robust enough to meet your needs even with inefficiencies. The result is presented in both Watts (W) and Kilowatts (kW), along with an estimate of the number of panels.

Why Accurate Sizing Matters:

• Cost-Effectiveness: An undersized system won't cover your energy needs, leaving you reliant on the grid. An oversized system costs more upfront than necessary.
• Energy Independence: A well-sized system maximizes your self-consumption of solar energy, reducing your electricity bills significantly.
• Environmental Impact: Optimizing your solar production directly contributes to reducing your carbon footprint.

While this calculator provides a strong estimate, it's always recommended to consult with a professional solar installer. They can conduct a detailed site assessment, consider factors like roof orientation, shading, local building codes, and future energy expansion plans to provide a precise system design and quotation.