Solar Panel Degradation & Performance Loss Calculator
ANA›Life Services Authority›National Calculator Authority›Solar Panel Degradation & Performance Loss Calculator
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Solar Panel Degradation & Performance Loss Calculator
Estimate how much power your solar panels lose over time due to natural degradation, and calculate remaining output and cumulative energy production over the system lifetime.
Initial Rated Power (W)
Nameplate wattage of one panel (STC rating)
Number of Panels
Total panels in your system
Annual Degradation Rate (%/year)
Typical range: 0.3%–0.8%/year; industry standard ~0.5%
First-Year Degradation (%)
Many panels degrade more in year 1 (LID effect); 0 if not applicable
Current System Age (years)
How many years the system has been operating
System Lifetime to Evaluate (years)
Typically 25–30 years for warranty analysis
Peak Sun Hours per Day (h/day)
Average daily peak sun hours for your location
System Efficiency / Performance Ratio (%)
Accounts for inverter, wiring, shading losses; typically 75%–85%
Electricity Rate ($/kWh)
Your local utility rate for savings estimation
Calculate
function solCalc() { const resultDiv = document.getElementById('sol-result');
// --- Read inputs --- const P0 = parseFloat(document.getElementById('sol-initial-power').value); const nPanels = parseFloat(document.getElementById('sol-num-panels').value); const dRate = parseFloat(document.getElementById('sol-degradation-rate').value); const firstLoss = parseFloat(document.getElementById('sol-first-year-loss').value); const age = parseFloat(document.getElementById('sol-system-age').value); const lifetime = parseFloat(document.getElementById('sol-lifetime').value); const psh = parseFloat(document.getElementById('sol-peak-sun-hours').value); const pr = parseFloat(document.getElementById('sol-system-efficiency').value); const rate = parseFloat(document.getElementById('sol-electricity-rate').value);
// --- Validation --- const errors = []; if (isNaN(P0) || P0 0 W."); if (isNaN(nPanels) || nPanels 5) errors.push("Annual Degradation Rate must be between 0.1% and 5%."); if (isNaN(firstLoss) || firstLoss 10) errors.push("First-Year Degradation must be between 0% and 10%."); if (isNaN(age) || age 50) errors.push("System Age must be between 0 and 50 years."); if (isNaN(lifetime) || lifetime 50) errors.push("System Lifetime must be between 1 and 50 years."); if (age > lifetime) errors.push("System Age cannot exceed System Lifetime."); if (isNaN(psh) || psh 12) errors.push("Peak Sun Hours must be between 0.5 and 12 h/day."); if (isNaN(pr) || pr 100) errors.push("System Efficiency must be between 50% and 100%."); if (isNaN(rate) || rate 0 $/kWh.");
if (errors.length > 0) { resultDiv.style.display = 'block'; resultDiv.innerHTML = 'Please fix the following:' + errors.map(e => '').join('') + ''; return; }
// --- Core Formulas --- // Degradation factor for year t (t=0 is end of year 1): // Year 1: P(1) = P0 * (1 - firstLoss/100) // Year t (t>1): P(t) = P(1) * (1 - dRate/100)^(t-1) // Combined: P(t) = P0 * (1 - L1) * (1 - d)^(t-1) for t >= 1 // where L1 = firstLoss/100, d = dRate/100
const L1 = firstLoss / 100; const d = dRate / 100; const prFrac = pr / 100;
// System initial DC capacity (kW) const systemP0_kW = (P0 * nPanels) / 1000;
// Power factor at a given year t (t >= 1) function powerFactor(t) { if (t === 0) return 1.0; return (1 - L1) * Math.pow(1 - d, t - 1); }
// Current power output (at system age) const currentFactor = (age === 0) ? 1.0 : powerFactor(age); const currentPower_kW = systemP0_kW * currentFactor; const powerLoss_kW = systemP0_kW - currentPower_kW; const powerLossPct = (1 - currentFactor) * 100;
// End-of-lifetime power output const eolFactor = powerFactor(lifetime); const eolPower_kW = systemP0_kW * eolFactor; const eolLossPct = (1 - eolFactor) * 100;
// Cumulative energy production over lifetime (kWh) // E_total = sum_{t=1}^{lifetime} P(t) * PSH * 365 * PR let cumulativeEnergy_kWh = 0; let yearlyData = []; for (let t = 1; t = 1e6) return fmt(n/1e6, 2) + ' M'; if (n >= 1e3) return fmt(n/1e3, 2) + ' k'; return fmt(n, 2) + ' '; }
// --- Build year-by-year table (show every 5 years + year 1 + current age) --- const tableYears = new Set([1]); for (let t = 5; t 0 && age a-b);
let tableRows = sortedYears.map(t => { const row = yearlyData[t-1]; const highlight = (t === age) ? ' style="background:#e8f5e9;font-weight:600;"' : ''; const label = (t === age) ? ' ★' : ''; return 'Year ' + t + label + '' + '' + fmt(row.factor * 100, 2) + '%' + '' + fmt(row.power_kW, 2) + ' kW' + '' + fmt(row.energy_kWh / 1000, 2) + ' MWh' + '$' + fmt(row.energy_kWh * rate) + ''; }).join('');
// --- Output --- resultDiv.style.display = 'block'; resultDiv.innerHTML = ` ### 📊 Solar Panel Degradation Results
Initial System Capacity ${fmt(systemP0_kW, 2)} kW
Current Output (Year ${age}) ${fmt(currentPower_kW, 2)} kW
Power Lost So Far ${fmt(powerLoss_kW, 2)} kW (${fmt(powerLossPct, 2)}%)
End-of-Life Output (Year ${lifetime}) ${fmt(eolPower_kW, 2)} kW (${fmt(eolFactor*100,2)}% of rated)
Total Power Loss at EOL ${fmt(eolLossPct, 2)}%
Current Annual Energy Output ${fmtK(currentAnnualEnergy_kWh)}Wh/year
Cumulative Energy (${lifetime} yrs) ${fmt(cumulativeEnergy_kWh/1000, 2)} MWh
Energy Lost to Degradation ${fmt(energyLost_kWh/1000, 2)} MWh ($${fmt(savingsLost)})
Lifetime Savings (${lifetime} yrs) $${fmt(totalSavings)}
Current Annual Savings $${fmt(currentAnnualSavings)}/year
#### 📅 Year-by-Year Performance
Year Output Factor System Power Annual Energy Annual Savings
${tableRows}
★ = Current system age
`; }
#### Formulas Used
Year-1 Power Factor (LID effect):
P(1) = P₀ × (1 − L₁)
where L₁ = first-year degradation rate (fraction)
Power Output at Year t (t ≥ 2):
P(t) = P₀ × (1 − L₁) × (1 − d)^(t−1)
where d = annual degradation rate (fraction), t = year number
Annual AC Energy Output at Year t:
E(t) = P(t) × PSH × 365 × PR
where PSH = peak sun hours/day, PR = performance ratio (system efficiency)
Cumulative Lifetime Energy:
E_total = Σ E(t) for t = 1 to N
Performance Ratio (PR): Accounts for inverter efficiency, wiring losses, temperature derating, and shading.
#### Assumptions & References
- Industry standard annual degradation rate is 0.5%/year per NREL (Jordan & Kurtz, 2013, Progress in Photovoltaics).
- First-year LID loss is typically 1%–3% for standard crystalline silicon panels; PERC and LeTID-resistant panels may show less.
- Most manufacturer warranties guarantee ≥80% output at 25 years, implying ~0.7%/year max degradation.
- Performance Ratio (PR) of 75%–85% is typical for well-maintained grid-tied systems (IEA PVPS Task 13).
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