Solar Inverter Sizing & Replacement Cost Calculator

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Solar Inverter Sizing & Replacement Cost Calculator

Determine the correct inverter size for your solar PV system and estimate total replacement costs including equipment and labor.

Total Solar Panel Capacity (kW)

System Derating Factor (%)

Accounts for temperature, wiring losses, soiling. Typical: 75–85%

Inverter Type

String Inverter Microinverter Hybrid / Battery-Ready Inverter Central Inverter (Commercial)

System Voltage (V DC)

48V (Small residential) 200–400V (Residential string) 600V (Standard residential/commercial) 1000V (Large commercial) 1500V (Utility scale)

Inverter Power Factor

Typical modern inverters: 0.95–0.99

Redundancy / Oversizing Buffer (%)

Extra capacity buffer. Recommended: 10–20%

Current Inverter Age (years, 0 if new)

Installation Region

USA – National Average USA – California USA – Texas USA – Florida USA – New York Europe (Average) Australia (Average) Other / Custom

Custom Inverter Cost ($/kW)

Labor Cost ($/hour)

Estimated Labor Hours

Typical replacement: 2–6 hrs residential, 6–16 hrs commercial

Calculate

document.getElementById('sol-install-region').addEventListener('change', function() { document.getElementById('sol-custom-cost-row').style.display = this.value === 'other' ? 'block' : 'none'; });

function solCalc() { const err = (msg) => { const r = document.getElementById('sol-result'); r.style.display = 'block'; r.innerHTML = '⚠ ' + msg + ''; };

const panelKW = parseFloat(document.getElementById('sol-panel-capacity').value); const derating = parseFloat(document.getElementById('sol-derating').value); const inverterType = document.getElementById('sol-inverter-type').value; const powerFactor = parseFloat(document.getElementById('sol-power-factor').value); const redundancy = parseFloat(document.getElementById('sol-redundancy').value); const age = parseFloat(document.getElementById('sol-inverter-age').value); const region = document.getElementById('sol-install-region').value; const laborRate = parseFloat(document.getElementById('sol-labor-cost').value); const laborHours = parseFloat(document.getElementById('sol-labor-hours').value);

if (isNaN(panelKW) || panelKW 100) return err("Derating factor must be between 50% and 100%."); if (isNaN(powerFactor) || powerFactor 1.0) return err("Power factor must be between 0.80 and 1.00."); if (isNaN(redundancy) || redundancy 50) return err("Redundancy buffer must be between 0% and 50%."); if (isNaN(age) || age 30) return err("Inverter age must be between 0 and 30 years."); if (isNaN(laborRate) || laborRate = recommendedKW) { selectedSize = standardSizes[i]; break; } } if (recommendedKW > 5000) selectedSize = Math.ceil(recommendedKW / 100) * 100;

// Clipping ratio (DC:AC ratio) — industry standard target: 1.1–1.3 const dcAcRatio = panelKW / selectedSize;

// ── COST FORMULA ──────────────────────────────────────────────────────────── // Base cost per kW by region (USD, 2024 market data) const regionCosts = { us_avg: 250, us_ca: 290, us_tx: 230, us_fl: 240, us_ny: 310, eu: 220, au: 270, other: null };

// Type multipliers const typeMultiplier = { string: 1.0, micro: 1.6, hybrid: 1.45, central: 0.75 };

let baseCostPerKW = region === 'other'
? parseFloat(document.getElementById('sol-custom-cost').value)
regionCosts[region];

baseCostPerKW *= typeMultiplier[inverterType];

// Equipment cost = selected_size_kW * cost_per_kW const equipmentCost = selectedSize * baseCostPerKW;

// Labor cost const laborCost = laborRate * laborHours;

// Disposal / removal fee (flat estimate based on size) const disposalFee = selectedSize 5) { urgencyLabel = "Low – Replacement not imminent"; urgencyColor = "#27ae60"; } else if (remainingLife > 2) { urgencyLabel = "Medium – Plan replacement soon"; urgencyColor = "#f39c12"; } else if (remainingLife > 0) { urgencyLabel = "High – Replacement recommended"; urgencyColor = "#e67e22"; } else { urgencyLabel = "Critical – Past expected lifespan"; urgencyColor = "#c0392b"; }

// Efficiency degradation estimate (approx 0.5% per year) const efficiencyLoss = Math.min(age * 0.5, 20).toFixed(1);

// Annual savings from new inverter (efficiency gain * system output estimate) // Assume 1200 kWh/kW/year average, $0.13/kWh const annualGenKWh = panelKW * 1200 * (derating / 100); const efficiencyGainFraction = parseFloat(efficiencyLoss) / 100; const annualSavings = annualGenKWh * efficiencyGainFraction * 0.13; const simplePayback = annualSavings > 0 ? (totalCost / annualSavings).toFixed(1) : "N/A";

const fmt = (n) => n.toLocaleString('en-US', {minimumFractionDigits:2, maximumFractionDigits:2}); const fmtKW = (n) => n % 1 === 0 ? n.toFixed(0) : n.toFixed(2);

const typeLabels = { string:"String Inverter", micro:"Microinverter", hybrid:"Hybrid/Battery-Ready", central:"Central Inverter" };

const r = document.getElementById('sol-result'); r.style.display = 'block'; r.innerHTML = ` ### ⚡ Inverter Sizing Results

DC Panel Capacity${fmtKW(panelKW)} kW Derated DC Output${fmtKW(dcOutputKW)} kW Required AC Output (after PF)${fmtKW(acRequiredKW)} kW With Redundancy Buffer (${redundancy}%)${fmtKW(recommendedKW)} kW ✓ Recommended Inverter Size${fmtKW(selectedSize)} kW DC:AC Clipping Ratio${dcAcRatio.toFixed(2)} ${dcAcRatio >= 1.1 && dcAcRatio Inverter Type${typeLabels[inverterType]}

### 💰 Replacement Cost Estimate

Equipment Cost (${fmtKW(selectedSize)} kW × $${fmt(baseCostPerKW)}/kW)$${fmt(equipmentCost)} Labor (${laborHours} hrs × $${fmt(laborRate)}/hr)$${fmt(laborCost)} Disposal / Removal Fee$${fmt(disposalFee)} Permit & Inspection (est.)$${fmt(permitFee)} Total Replacement Cost$${fmt(totalCost)}

### 🕑 Inverter Lifespan & Urgency

Current Age${age} years Typical Lifespan (${typeLabels[inverterType]})${typicalLife} years Life Used${lifePercent}% Estimated Remaining Life${remainingLife} years Estimated Efficiency Loss~${efficiencyLoss}% Replacement Urgency${urgencyLabel}

${age > 0 ? ` ### 📈 ROI from Replacement

Est. Annual Generation${Math.round(annualGenKWh).toLocaleString()} kWh Efficiency Recovery Gain${efficiencyLoss}% Est. Annual Savings (@ $0.13/kWh)$${fmt(annualSavings)} Simple Payback Period${simplePayback} years : ''}; }

#### Formulas Used

1. Derated DC Output: DCoutput = Panel Capacity (kW) × (Derating Factor / 100)

2. Required AC Output: ACrequired = DCoutput / Power Factor

3. Recommended Inverter Size (with buffer): Inverterrecommended = ACrequired × (1 + Redundancy% / 100) → Rounded up to nearest standard commercial inverter size

4. DC:AC Clipping Ratio: Ratio = Panel Capacity (kW) / Selected Inverter Size (kW) Optimal range: 1.10 – 1.30 per NREL guidelines

5. Total Replacement Cost: Total = (Inverter kW × Cost/kW × Type Multiplier) + (Labor Hours × Labor Rate) + Disposal Fee + Permit Fee

6. Efficiency Degradation: Loss ≈ 0.5% per year of operation (capped at 20%)

7. Annual Savings from Replacement: Savings = Annual Generation (kWh) × Efficiency Gain Fraction × $0.13/kWh Annual Generation = Panel kW × 1,200 kWh/kW/yr × Derating Factor

#### Assumptions & References

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