Home Charging Station ROI Calculator
ANA›Life Services Authority›National Calculator Authority›Home Charging Station ROI Calculator
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Home Charging Station ROI Calculator
Estimate your payback period and lifetime savings from installing a Level 2 home EV charging station compared to public charging.
Total Installation Cost ($)
Federal Tax Credit / Rebates ($)
Annual Miles Driven
EV Efficiency (miles per kWh)
Home Electricity Rate ($/kWh)
Public Charging Rate ($/kWh equivalent)
% of Charging Done at Home (after install)
% of Charging Done at Home (before install)
Charger Lifespan (years)
Annual Electricity Price Inflation (%)
Calculate ROI
function homCalc() { // --- Read inputs --- const installCost = parseFloat(document.getElementById('hom-install-cost').value); const federalCredit = parseFloat(document.getElementById('hom-federal-credit').value); const annualMiles = parseFloat(document.getElementById('hom-annual-miles').value); const evEff = parseFloat(document.getElementById('hom-ev-efficiency').value); const homeRate = parseFloat(document.getElementById('hom-home-rate').value); const publicRate = parseFloat(document.getElementById('hom-public-rate').value); const pctHomeAfter = parseFloat(document.getElementById('hom-pct-home').value) / 100; const pctHomeBefore = parseFloat(document.getElementById('hom-pct-home-before').value) / 100; const chargerLife = parseInt(document.getElementById('hom-charger-life').value); const elecInflation = parseFloat(document.getElementById('hom-elec-inflation').value) / 100;
// --- Validation --- const errors = []; if (isNaN(installCost) || installCost installCost) errors.push("Tax credit cannot exceed installation cost."); if (isNaN(annualMiles) || annualMiles 0."); if (isNaN(evEff) || evEff 0."); if (isNaN(homeRate) || homeRate 0."); if (isNaN(publicRate) || publicRate 0."); if (isNaN(pctHomeAfter) || pctHomeAfter 1) errors.push("% home charging after must be 1–100."); if (isNaN(pctHomeBefore) || pctHomeBefore 1) errors.push("% home charging before must be 0–100."); if (pctHomeBefore >= pctHomeAfter) errors.push("Home charging % after install must exceed % before install."); if (isNaN(chargerLife) || chargerLife 0) { document.getElementById('hom-result').innerHTML = 'Please fix the following:' + errors.map(e => '').join('') + ''; return; }
// --- Core Calculations --- // Total annual kWh needed const annualKwh = annualMiles / evEff;
// Annual charging cost BEFORE install // pctHomeBefore at home rate, rest at public rate const annualCostBefore = annualKwh * (pctHomeBefore * homeRate + (1 - pctHomeBefore) * publicRate);
// Annual charging cost AFTER install (Year 1, base rates) const annualCostAfterY1 = annualKwh * (pctHomeAfter * homeRate + (1 - pctHomeAfter) * publicRate);
// Net installation cost after credits const netInstallCost = installCost - federalCredit;
// Year-by-year analysis with electricity inflation let cumulativeSavings = 0; let paybackYear = null; let paybackMonths = null; let totalSavings = 0; const yearData = [];
for (let y = 1; y = net install cost if (paybackYear === null && cumulativeSavings >= netInstallCost) { const prevCumulative = cumulativeSavings - savingsY; const fraction = (netInstallCost - prevCumulative) / savingsY; paybackYear = (y - 1) + fraction; paybackMonths = paybackYear * 12; }
yearData.push({ year: y, savingsY: savingsY, cumulative: cumulativeSavings, netPosition: cumulativeSavings - netInstallCost }); }
// Lifetime net benefit const lifetimeNetBenefit = totalSavings - netInstallCost;
// Simple ROI % const roi = netInstallCost > 0 ? (lifetimeNetBenefit / netInstallCost) * 100 : Infinity;
// Annual savings Year 1 const annualSavingsY1 = annualCostBefore - annualCostAfterY1;
// --- Format helpers --- const fmt = v => '$' + v.toFixed(2).replace(/\B(?=(\d{3})+(?!\d))/g, ','); const fmt0 = v => '$' + Math.round(v).toLocaleString();
// Build payback string let paybackStr; if (paybackYear === null) { paybackStr = 'Not recovered within charger lifespan (' + chargerLife + ' yrs)'; } else if (paybackYear Less than 1 month'; } else { const py = Math.floor(paybackYear); const pm = Math.round((paybackYear - py) * 12); paybackStr = '' + (py > 0 ? py + ' yr' + (py !== 1 ? 's' : '') : '') + (py > 0 && pm > 0 ? ' ' : '') + (pm > 0 ? pm + ' mo' + (pm !== 1 ? 's' : '') : '') + ''; }
// Build year table (show all years, max 15 rows before scrolling) let tableRows = ''; for (const d of yearData) { const netColor = d.netPosition >= 0 ? '#27ae60' : '#c0392b'; tableRows += '' + '' + d.year + '' + '' + fmt(d.savingsY) + '' + '' + fmt(d.cumulative) + '' + '' + fmt(d.netPosition) + '' + ''; }
- const tableStyle = chargerLife > 12
- ? 'max-height:260px;overflow-y:auto;display:block;'
- '';
document.getElementById('hom-result').innerHTML = ` ### ROI Summary
Net Installation Cost ${fmt0(netInstallCost)} Annual Savings — Year 1 ${fmt(annualSavingsY1)} Annual kWh Required ${Math.round(annualKwh).toLocaleString()} kWh Payback Period ${paybackStr} Lifetime Savings (${chargerLife} yrs) ${fmt0(totalSavings)} Lifetime Net Benefit =0?'#27ae60':'#c0392b'}">${fmt0(lifetimeNetBenefit)} ROI over Lifespan ${netInstallCost > 0 ? roi.toFixed(1) + '%' : 'N/A'}
#### Year-by-Year Breakdown
Year Annual Savings Cumulative Savings Net Position
${tableRows}
Net Position = Cumulative Savings − Net Installation Cost. Positive = recovered investment.
`; }
#### Formulas Used
Annual kWh: Annual kWh = Annual Miles ÷ EV Efficiency (mi/kWh)
Annual Charging Cost (any scenario): Cost = Annual kWh × [(%Home × Home Rate) + (%Public × Public Rate)] where %Public = 1 − %Home
Annual Savings (Year y): Savingsy = CostBefore,y − CostAfter,y Rates inflate each year: Ratey = Rate1 × (1 + Inflation%)y−1
Net Installation Cost: Net Cost = Installation Cost − Federal Credit − Rebates
Payback Period: Fractional year when Cumulative Savings ≥ Net Installation Cost Payback = (y−1) + (Net Cost − Cumulativey−1) ÷ Savingsy
Lifetime Net Benefit: Net Benefit = Σ Savingsy (y=1…N) − Net Installation Cost
ROI: ROI = (Lifetime Net Benefit ÷ Net Installation Cost) × 100%
#### Assumptions & References
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