Your estimated savings and system cost will appear here.
Understanding Your Solar Panel Estimate
This Solar Estimator Calculator helps you get a preliminary idea of the potential benefits and costs associated with installing a solar panel system for your home. It considers several key factors to provide an estimate of your annual electricity generation, potential savings, and the upfront investment.
How it Works: The Math Behind the Estimate
The calculator performs several calculations to arrive at its estimate:
1. Annual Electricity Consumption (kWh):
First, we determine your household's approximate annual electricity usage. This is derived from your annual electricity bill and the price you pay per kilowatt-hour (kWh).
var annualConsumption = parseFloat(document.getElementById('annualElectricityBill').value) / parseFloat(document.getElementById('averagePricePerKwh').value);
// Result is in kWh
2. Annual Energy Production (kWh):
This estimates how much electricity your proposed solar system can generate in a year. It depends on the system size (in kilowatts, kW), the number of peak sun hours your location receives daily, and the system's performance ratio (which accounts for inefficiencies like inverter losses, wiring, and temperature). For simplicity, we'll use a general performance ratio.
var systemSizeKw = parseFloat(document.getElementById('systemSize').value);
var dailySunHours = parseFloat(document.getElementById('annualSunHours').value);
var annualProduction = systemSizeKw * 1000 * dailySunHours * 365 * 0.85; // 0.85 is a typical performance ratio
// Result is in kWh
3. Potential Annual Savings ($):
This is the estimated amount you could save on your electricity bills by generating your own power. It's calculated by multiplying your potential annual energy production by the average price you pay per kWh.
var potentialSavings = annualProduction / 1000 * parseFloat(document.getElementById('averagePricePerKwh').value);
// Result is in $
4. System Cost ($):
This estimates the total upfront cost of purchasing and installing the solar panel system. It's based on the system size and the cost per watt.
var systemSizeKw = parseFloat(document.getElementById('systemSize').value);
var costPerWatt = parseFloat(document.getElementById('systemCostPerWatt').value);
var totalSystemCost = systemSizeKw * 1000 * costPerWatt;
// Result is in $
5. Net Savings (First Year):
This is a simplified view of the financial benefit in the first year, comparing your potential savings against the system cost.
var firstYearNetSavings = potentialSavings – totalSystemCost;
// Result is in $
Factors Not Included:
This calculator provides a basic estimate. Several other factors can influence the actual outcome, including:
Net Metering Policies: How your utility company credits you for excess energy sent back to the grid.
Incentives and Rebates: Federal, state, and local tax credits or rebates can significantly reduce the net cost.
Shading and Roof Orientation: The actual angle and direction of your roof, as well as any shading, impact production.
Maintenance Costs: While generally low, occasional cleaning or repairs might be needed.
System Lifespan: Solar panels typically last 25-30 years, meaning savings accrue over the long term.
Inflation: Electricity prices are likely to increase over time, making solar savings even more valuable.
System Degradation: Panels slowly lose efficiency over time, accounted for by the degradation rate in more advanced calculations.
Disclaimer: This tool is for estimation purposes only. For an accurate assessment and quote, please consult with a qualified solar installation professional.
function calculateSolarEstimate() {
var annualBill = parseFloat(document.getElementById('annualElectricityBill').value);
var avgPricePerKwh = parseFloat(document.getElementById('averagePricePerKwh').value);
var systemSizeKw = parseFloat(document.getElementById('systemSize').value);
var dailySunHours = parseFloat(document.getElementById('annualSunHours').value);
var degradationRate = parseFloat(document.getElementById('systemDegradationRate').value);
var costPerWatt = parseFloat(document.getElementById('systemCostPerWatt').value);
var resultDiv = document.getElementById('result');
resultDiv.innerHTML = 'Your estimated savings and system cost will appear here.'; // Reset message
// Input validation
if (isNaN(annualBill) || isNaN(avgPricePerKwh) || isNaN(systemSizeKw) || isNaN(dailySunHours) || isNaN(degradationRate) || isNaN(costPerWatt) ||
annualBill <= 0 || avgPricePerKwh <= 0 || systemSizeKw <= 0 || dailySunHours <= 0 || costPerWatt <= 0) {
resultDiv.innerHTML = 'Please enter valid positive numbers for all fields.';
return;
}
// — Calculations —
// 1. Annual Electricity Consumption (kWh)
var annualConsumptionKwh = annualBill / avgPricePerKwh;
// 2. Annual Energy Production (kWh) – Simplified, assumes a standard performance ratio
// We'll use a performance ratio of 0.85 for typical system losses (inverter, wiring, temperature)
var performanceRatio = 0.85;
var annualProductionKwh = systemSizeKw * 1000 * dailySunHours * 365 * performanceRatio;
// 3. Potential Annual Savings ($) – Based on current electricity cost
var potentialAnnualSavings = annualProductionKwh * avgPricePerKwh;
// 4. Total System Cost ($)
var totalSystemCost = systemSizeKw * 1000 * costPerWatt;
// 5. First Year Net Savings ($)
var firstYearNetSavings = potentialAnnualSavings – totalSystemCost;
// 6. Payback Period (Years) – Simplified, ignores degradation and electricity price increases
var paybackPeriodYears = totalSystemCost / potentialAnnualSavings;
if (paybackPeriodYears < 1) paybackPeriodYears = 1; // Avoid showing less than 1 year payback
// Display Results
var outputHTML = '
Your Solar Estimate:
';
outputHTML += 'Estimated Annual Electricity Consumption: ' + annualConsumptionKwh.toFixed(0) + ' kWh';
outputHTML += 'Estimated Annual Solar Production: ' + annualProductionKwh.toFixed(0) + ' kWh';
outputHTML += 'Estimated First Year Savings: $' + potentialAnnualSavings.toFixed(2) + '';
outputHTML += 'Estimated Total System Cost: $' + totalSystemCost.toFixed(2) + '';
outputHTML += 'Estimated First Year Net Position: = 0 ? '#28a745' : '#dc3545') + ';">$' + firstYearNetSavings.toFixed(2) + '';
outputHTML += 'Estimated Simple Payback Period: ' + paybackPeriodYears.toFixed(1) + ' years';
outputHTML += 'Note: This is a simplified estimate. Actual results may vary.';
resultDiv.innerHTML = outputHTML;
}