Solar Electricity Calculator

Solar Electricity Calculator

Your Solar Estimation

System Size Needed: kW

Number of Panels:

Annual Energy Generation: kWh

Est. Annual Savings: $

function calculateSolar() { var monthlyUsage = parseFloat(document.getElementById('monthlyUsage').value); var costPerKwh = parseFloat(document.getElementById('costPerKwh').value); var dailySunHours = parseFloat(document.getElementById('dailySunHours').value); var panelWattage = parseFloat(document.getElementById('panelWattage').value); if (isNaN(monthlyUsage) || isNaN(costPerKwh) || isNaN(dailySunHours) || isNaN(panelWattage) || monthlyUsage <= 0) { alert("Please enter valid positive numbers for all fields."); return; } // Calculations // Efficiency factor (standard losses for roof angle, wiring, inverter is ~23%) var systemEfficiency = 0.77; // Daily kWh required var dailyKwhNeeded = monthlyUsage / 30.42; // Required DC System Size (kW) = Daily kWh / (Sun Hours * Efficiency) var systemSizeKw = dailyKwhNeeded / (dailySunHours * systemEfficiency); // Number of panels var numPanels = Math.ceil((systemSizeKw * 1000) / panelWattage); // Annual generation var annualGen = systemSizeKw * dailySunHours * systemEfficiency * 365; // Annual savings var annualSavings = annualGen * costPerKwh; // Display document.getElementById('resSystemSize').innerText = systemSizeKw.toFixed(2); document.getElementById('resNumPanels').innerText = numPanels; document.getElementById('resAnnualGen').innerText = Math.round(annualGen).toLocaleString(); document.getElementById('resSavings').innerText = annualSavings.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}); document.getElementById('solar-results').style.display = 'block'; }

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Switching to solar power is one of the most effective ways to reduce your carbon footprint and eliminate monthly utility bills. However, determining the correct system size is crucial to ensure you don't under-produce or spend too much on an oversized system. This solar electricity calculator helps you bridge the gap between your current consumption and your future energy independence.

Key Components of Solar Calculation

• Monthly Consumption (kWh): This is the amount of electricity your home consumes, found on your utility bill. We use this to determine the daily target.
• Peak Sun Hours: This is not just "daylight." It refers to the intensity of sunlight. A location might have 12 hours of daylight but only 5 "peak sun hours" where the radiation is strong enough to produce maximum power.
• System Efficiency: No solar system is 100% efficient. Energy is lost through DC-to-AC conversion (inverters), wiring, and environmental factors like dust or heat. Our calculator assumes a standard 77% efficiency rate.
• Panel Wattage: Modern residential panels typically range from 350W to 450W. Higher wattage means you need fewer physical panels on your roof.

The Math Behind the Solar Calculator

To find your required system size manually, you can use the following formula:

System Size (kW) = (Monthly kWh ÷ 30 Days) ÷ (Daily Sun Hours × 0.77 Efficiency)

Example Calculation

Suppose you live in a region with 5 peak sun hours per day and your average monthly usage is 900 kWh. You plan to use 400W panels.

1. Daily Need: 900 kWh / 30 days = 30 kWh per day.
2. Adjusted Need: 30 kWh / (5 sun hours × 0.77 efficiency) = 7.79 kW system.
3. Panel Count: (7.79 kW × 1000) / 400W = 19.47, so you would need 20 panels.

Benefits of Solar Energy

By installing a system sized correctly to your needs, you can achieve a "Net Zero" status where your panels produce as much energy as you consume over the course of a year. In many regions, "Net Metering" allows you to sell excess power back to the grid during the day and pull it back at night, effectively using the utility grid as a giant battery.