NJ Solar Panel System Size and Savings Calculator

ANA›Life Services Authority›National Calculator Authority›NJ Solar Panel System Size and Savings Calculator

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NJ Solar Panel System Size and Savings Calculator

Estimate the ideal solar panel system size for your New Jersey home and calculate your projected annual savings, including NJ-specific incentives like the Transition Renewable Energy Certificate (TREC) program and net metering.

Average Monthly Electric Bill ($)

Electricity Rate ($/kWh)

NJ average: ~$0.17/kWh (2024)

Available Roof Area (sq ft)

Primary Roof Direction

South (Optimal) Southeast / Southwest East / West Northeast / Northwest North (Least Optimal)

Shading Factor

No Shading (Full Sun) Minimal Shading Moderate Shading Heavy Shading

Panel Wattage (W per panel)

400W (Standard) 350W (Economy) 450W (Premium) 500W (High-Efficiency)

Estimated System Cost per Watt ($)

NJ average: ~$2.80–$3.20/W installed (2024)

Include NJ TREC Incentive?

Yes – Enrolled in TREC Program No

TREC pays ~$90 per MWh generated for 15 years (community solar / grid-tied)

Calculate

function njSolarCalc() { // --- Gather Inputs --- var monthlyBill = parseFloat(document.getElementById('nj-monthly-bill').value); var elecRate = parseFloat(document.getElementById('nj-electricity-rate').value); var roofArea = parseFloat(document.getElementById('nj-roof-area').value); var roofFactor = parseFloat(document.getElementById('nj-roof-direction').value); var shadingFactor = parseFloat(document.getElementById('nj-shading').value); var panelWattage = parseFloat(document.getElementById('nj-panel-wattage').value); var costPerWatt = parseFloat(document.getElementById('nj-system-cost').value); var trecEnabled = parseInt(document.getElementById('nj-trec').value);

// --- Validation --- var errors = []; if (isNaN(monthlyBill) || monthlyBill 2000) errors.push("Monthly electric bill must be between $10 and $2,000."); if (isNaN(elecRate) || elecRate 0.50) errors.push("Electricity rate must be between $0.05 and $0.50 per kWh."); if (isNaN(roofArea) || roofArea 5000) errors.push("Available roof area must be between 100 and 5,000 sq ft."); if (isNaN(costPerWatt) || costPerWatt 6.00) errors.push("System cost per watt must be between $1.50 and $6.00.");

if (errors.length > 0) { document.getElementById('nj-result').innerHTML = 'Please fix the following:' + errors.map(function(e){ return ''; }).join('') + ''; return; }

// --- Constants (NJ-Specific) --- var peakSunHours = 4.21; // NJ average peak sun hours per day (NREL PVWatts, NJ) var systemEfficiency = 0.80; // Accounts for inverter loss, wiring, temperature (~80% derate) var sqFtPerPanel = 17.5; // Approx area per 400W panel (varies slightly by wattage) var federalITCRate = 0.30; // 30% Federal Investment Tax Credit (IRA 2022–2032) var njSalesTaxExempt = 0.06625;// NJ 6.625% sales tax exemption on solar equipment var trecRatePerMWh = 90.00; // NJ TREC rate $/MWh (approximate 2024 value) var trecYears = 15; // TREC contract duration var netMeteringRate = elecRate; // NJ full retail net metering (1:1 credit) var annualDegradation = 0.005; // 0.5% annual panel degradation var systemLifeYears = 25;

// --- Step 1: Annual Energy Consumption --- // Annual kWh = (Monthly Bill / Electricity Rate) * 12 var monthlyKwh = monthlyBill / elecRate; var annualKwh = monthlyKwh * 12;

// --- Step 2: Required System Size (kW DC) --- // System Size (kW) = Annual kWh / (Peak Sun Hours/day * 365 * System Efficiency) var systemSizeKw = annualKwh / (peakSunHours * 365 * systemEfficiency);

// --- Step 3: Roof Capacity Check --- // Adjust sq ft per panel proportionally to selected wattage vs 400W baseline var adjustedSqFtPerPanel = sqFtPerPanel * (panelWattage / 400); var maxPanelsByRoof = Math.floor(roofArea / adjustedSqFtPerPanel); var maxSystemKwByRoof = (maxPanelsByRoof * panelWattage) / 1000;

// Apply roof direction and shading to max roof capacity var effectiveRoofKw = maxSystemKwByRoof * roofFactor * shadingFactor;

// Final recommended system size = min of needed vs roof capacity var recommendedKw = Math.min(systemSizeKw, effectiveRoofKw); var recommendedKw = Math.round(recommendedKw * 100) / 100;

// Number of panels var numPanels = Math.ceil((recommendedKw * 1000) / panelWattage);

// Recalculate actual system size based on whole panels var actualSystemKw = (numPanels * panelWattage) / 1000;

// --- Step 4: Annual Energy Production --- // Annual Production (kWh) = System Size (kW) * Peak Sun Hours * 365 * Efficiency * Roof Factor * Shading var annualProduction = actualSystemKw * peakSunHours * 365 * systemEfficiency * roofFactor * shadingFactor;

// --- Step 5: Gross System Cost --- var grossCost = actualSystemKw * 1000 * costPerWatt;

// --- Step 6: Incentives --- // Federal ITC: 30% of gross cost var federalITC = grossCost * federalITCRate;

// NJ Sales Tax Exemption: 6.625% of gross cost var njSalesTax = grossCost * njSalesTaxExempt;

// NJ Property Tax Exemption (added home value not taxed — informational) // Estimated added home value: ~$3/W (Lawrence Berkeley National Lab) var addedHomeValue = actualSystemKw * 1000 * 3.00;

// Net Cost after ITC and Sales Tax var netCost = grossCost - federalITC - njSalesTax;

// --- Step 7: Annual Savings from Net Metering --- // Savings = Annual Production * Electricity Rate (full retail net metering in NJ) var annualNetMeteringSavings = annualProduction * netMeteringRate;

// --- Step 8: TREC Income --- // TREC = Annual Production (MWh) * TREC Rate * 15 years (total) var annualTrecIncome = trecEnabled ? (annualProduction / 1000) * trecRatePerMWh : 0; var totalTrecIncome = annualTrecIncome * trecYears;

// --- Step 9: Total First-Year Savings --- var firstYearSavings = annualNetMeteringSavings + annualTrecIncome;

// --- Step 10: Simple Payback Period --- // Payback = Net Cost / Annual Savings (Year 1) var paybackYears = firstYearSavings > 0 ? netCost / firstYearSavings : 0;

// --- Step 11: 25-Year Lifetime Savings (with degradation) --- // Sum of geometric series: S = A * (1 - r^n) / (1 - r), r = (1 - degradation) var r = 1 - annualDegradation; var lifetimeProduction = annualProduction * (1 - Math.pow(r, systemLifeYears)) / (1 - r); var lifetimeNetMeteringSavings = lifetimeProduction * netMeteringRate; var lifetimeTrecIncome = trecEnabled ? (annualProduction / 1000) * trecRatePerMWh * trecYears : 0; var lifetimeSavings = lifetimeNetMeteringSavings + lifetimeTrecIncome; var lifetimeROI = netCost > 0 ? ((lifetimeSavings - netCost) / netCost) * 100 : 0;

// --- Step 12: CO2 Offset --- // NJ grid emission factor: ~0.386 lbs CO2/kWh (EPA eGRID 2022, RFCE region) var co2PerKwh = 0.386; var annualCO2Offset = (annualProduction * co2PerKwh) / 2204.62; // convert lbs to metric tons

// --- Coverage Percentage --- var coveragePct = Math.min((annualProduction / annualKwh) * 100, 100);

// --- Roof Constraint Warning ---
var roofConstrained = (effectiveRoofKw ⚠️ Your roof area limits the system to ' + fmt(effectiveRoofKw,2) + ' kW, which covers ' + fmt(coveragePct,1) + '% of your energy needs. Consider energy efficiency upgrades to reduce consumption.'
'';
var trecRow = trecEnabled
? 'Annual TREC Income' + fmtD(annualTrecIncome) + '/yr' +
'Total TREC Income (15 yrs)' + fmtK(totalTrecIncome) + ''
'TREC IncomeNot included';

document.getElementById('nj-result').innerHTML = '### ⚡ Your NJ Solar Estimate ' + roofWarning + '' + 'System Specifications' + 'Recommended System Size' + fmt(actualSystemKw,2) + ' kW DC' + 'Number of Panels' + numPanels + ' panels × ' + panelWattage + 'W' + 'Annual Energy Production' + fmt(annualProduction,0) + ' kWh/yr' + '% of Energy Needs Covered' + fmt(coveragePct,1) + '%' + 'Costs & Incentives' + 'Gross System Cost' + fmtK(grossCost) + '' + 'Federal ITC (30%)− ' + fmtK(federalITC) + '' + 'NJ Sales Tax Exemption (6.625%)− ' + fmtK(njSalesTax) + '' + 'Net Cost After Incentives' + fmtK(netCost) + '' + 'Est. Added Home Value (not taxed)+ ' + fmtK(addedHomeValue) + '' + 'Annual Savings & Income' + 'Annual Net Metering Savings' + fmtD(annualNetMeteringSavings) + '/yr' + trecRow + 'Total First-Year Benefit' + fmtD(firstYearSavings) + '/yr' + 'Long-Term Performance' + 'Simple Payback Period' + fmt(paybackYears,1) + ' years' + '25-Year Lifetime Savings' + fmtK(lifetimeSavings) + '' + '25-Year Net ROI' + fmt(lifetimeROI,1) + '%' + 'Annual CO₂ Offset' + fmt(annualCO2Offset,2) + ' metric tons/yr' + '' + '* Estimates are for planning purposes. Actual results vary based on installation, shading, utility rates, and tax situation. Consult a licensed NJ solar installer and tax professional.

'; }

#### Formulas Used

Annual Energy Consumption: Annual kWh = (Monthly Bill ÷ Electricity Rate) × 12

Required System Size: System Size (kW) = Annual kWh ÷ (Peak Sun Hours × 365 × System Efficiency Derate) NJ Peak Sun Hours = 4.21 hrs/day (NREL PVWatts, statewide average) System Efficiency Derate = 0.80 (inverter losses, wiring, temperature, soiling)

Roof Capacity: Max Panels = Floor(Roof Area ÷ Area per Panel) Effective Roof Capacity (kW) = (Max Panels × Panel Wattage ÷ 1000) × Roof Direction Factor × Shading Factor

Annual Energy Production: Production (kWh) = System Size (kW) × 4.21 × 365 × 0.80 × Roof Direction Factor × Shading Factor

Net Cost: Net Cost = Gross Cost − Federal ITC (30%) − NJ Sales Tax Exemption (6.625%)

Annual Net Metering Savings: Savings = Annual Production (kWh) × Electricity Rate ($/kWh) NJ uses full retail-rate net metering (1:1 credit)

TREC Income: Annual TREC = (Annual Production ÷ 1,000) × $90/MWh Total TREC = Annual TREC × 15 years

Simple Payback: Payback (years) = Net Cost ÷ First-Year Annual Benefit

25-Year Lifetime Savings (with 0.5%/yr degradation): Lifetime Production = Annual Production × (1 − 0.995²⁵) ÷ (1 − 0.995) Lifetime Savings = Lifetime Production × Electricity Rate + Total TREC Income

CO₂ Offset: Annual CO₂ (metric tons) = Annual Production (kWh) × 0.386 lbs/kWh ÷ 2,204.62

#### Assumptions & References

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