Investing in solar energy is a significant decision that can lead to substantial long-term savings and environmental benefits. This calculator provides a preliminary estimate to help you understand the potential costs, savings, and system size needed for your home.
How the Estimate is Calculated:
The calculation involves several key factors that determine the performance and economic viability of a solar energy system:
Annual Electricity Usage (kWh): This is the total amount of electricity your household consumes in a year, typically found on your utility bills. It's the baseline for determining how much solar power you need.
Desired System Size (kW): This is the capacity of the solar panel system you're considering. A larger system can generate more electricity but will have a higher upfront cost. The calculator uses this to estimate potential energy generation.
Average Peak Sun Hours per Day: This measures the average daily intensity of sunlight in your specific location. More sun hours mean more electricity generated by your panels. This is a critical factor for performance.
System Cost per Watt ($): This represents the total cost of the solar installation, including panels, inverters, mounting hardware, and labor, divided by the system's total wattage. This is your upfront investment.
Your Electricity Rate ($/kWh): The price you currently pay your utility company for each kilowatt-hour of electricity. The higher this rate, the more you'll save by generating your own power.
Available Incentives (%): These are government tax credits, rebates, or local programs that reduce the net cost of your solar system. We apply this percentage to the gross system cost to find the net cost.
The Math Behind the Estimate:
The calculator uses the following simplified formulas:
Estimated Annual Generation (kWh):Annual Generation = System Size (kW) * Average Peak Sun Hours/Day * 365 days/year * System Efficiency Factor
(A typical efficiency factor of 0.77 is used here to account for system losses like shading, inverter efficiency, and temperature.)
Gross System Cost ($):Gross Cost = System Size (kW) * 1000 (to convert kW to W) * System Cost per Watt ($/W)
Net System Cost ($):Net Cost = Gross Cost * (1 - Incentive Rate / 100)
Estimated Annual Savings ($):Annual Savings = MIN(Annual Generation, Annual Electricity Usage) * Electricity Rate ($/kWh)
(We cap savings at your actual annual usage to avoid overestimating if the system generates more than you consume.)
Payback Period (Years):Payback Period = Net System Cost / Annual Savings
(This estimates how long it will take for your savings to equal your net investment.)
Use Cases for This Calculator:
Budgeting: Get a realistic idea of the upfront investment and potential net cost after incentives.
Savings Potential: Understand how much you could save on your electricity bills annually.
System Sizing: Explore how different system sizes impact generation and savings.
Incentive Impact: See how much available incentives reduce the overall cost.
Informed Decisions: Use the estimates as a starting point for discussions with solar installers.
Disclaimer: This calculator provides an estimate based on the information you provide. Actual system performance and savings may vary due to factors like specific equipment, installation quality, shading, weather patterns, and changes in electricity rates. Always consult with certified solar professionals for a personalized assessment.
function calculateSolarEstimate() {
var annualEnergyUsage = parseFloat(document.getElementById("annualEnergyUsage").value);
var systemSize = parseFloat(document.getElementById("systemSize").value); // in kW
var sunHours = parseFloat(document.getElementById("sunHours").value);
var systemCostPerWatt = parseFloat(document.getElementById("systemCostPerWatt").value); // in $/W
var electricityRate = parseFloat(document.getElementById("electricityRate").value); // in $/kWh
var incentiveRate = parseFloat(document.getElementById("incentiveRate").value); // in %
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = "; // Clear previous results
// Input validation
if (isNaN(annualEnergyUsage) || annualEnergyUsage <= 0 ||
isNaN(systemSize) || systemSize <= 0 ||
isNaN(sunHours) || sunHours <= 0 ||
isNaN(systemCostPerWatt) || systemCostPerWatt <= 0 ||
isNaN(electricityRate) || electricityRate <= 0 ||
isNaN(incentiveRate) || incentiveRate 100) {
resultDiv.innerHTML = "Please enter valid positive numbers for all fields (Incentives can be 0-100).";
return;
}
// Constants
var systemEfficiencyFactor = 0.77; // Accounts for losses (shading, inverter, temp, etc.)
// Calculations
var estimatedAnnualGeneration = systemSize * 1000 * sunHours * 365 * systemEfficiencyFactor / 1000; // Convert W to kW in calculation
var grossSystemCost = systemSize * 1000 * systemCostPerWatt; // System size in W * cost per W
var netSystemCost = grossSystemCost * (1 – incentiveRate / 100);
var estimatedAnnualSavings = Math.min(estimatedAnnualGeneration, annualEnergyUsage) * electricityRate;
var paybackPeriod = (netSystemCost > 0 && estimatedAnnualSavings > 0) ? netSystemCost / estimatedAnnualSavings : Infinity;
// Display Results
var htmlOutput = "