Home Systems Depreciation Calculator

ANA›Life Services Authority›National Calculator Authority›Home Systems Depreciation Calculator

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Home Systems Depreciation Calculator

Estimate the current depreciated (actual cash) value of major home systems using age, condition, and replacement cost. Useful for insurance claims, home sales, and budgeting.

Home System

HVAC / Central Air & Heat Furnace / Boiler Water Heater (Tank) Water Heater (Tankless) Roof (Asphalt Shingles) Roof (Metal) Electrical Panel / Wiring Plumbing System Sewer / Septic System Windows (Double-Pane) Insulation Garage Door & Opener

Replacement Cost ($)

Current cost to replace the system with a new equivalent.

Current Age of System (years)

Expected Useful Life (years)

Auto-filled by system type; you may override.

Condition

Excellent – well-maintained, no issues Good – minor wear, fully functional Fair – noticeable wear, some repairs needed Poor – significant deterioration

Condition applies an adjustment factor to the depreciated value.

Salvage Value (%) (optional)

Percentage of replacement cost retained at end of useful life (typically 0–15%).

Calculate Depreciation

(function() {

// Typical useful life in years by system (industry standard / ISO / Appraisal Institute) const homLifeMap = { hvac: { life: 15, label: "~15 yrs (industry avg)" }, furnace: { life: 20, label: "~20 yrs" }, water_heater: { life: 12, label: "~12 yrs" }, water_heater_tank: { life: 20, label: "~20 yrs (tankless)" }, roof_asphalt: { life: 25, label: "~25 yrs" }, roof_metal: { life: 50, label: "~50 yrs" }, electrical: { life: 40, label: "~40 yrs" }, plumbing: { life: 50, label: "~50 yrs" }, sewer: { life: 40, label: "~40 yrs" }, windows: { life: 20, label: "~20 yrs" }, insulation: { life: 30, label: "~30 yrs" }, garage_door: { life: 15, label: "~15 yrs" } };

// Condition multipliers (applied to depreciated value) const homConditionMap = { excellent: 1.10, good: 1.00, fair: 0.85, poor: 0.70 };

window.homUpdateLife = function() { const sys = document.getElementById("hom-system").value; const info = homLifeMap[sys]; if (info) { document.getElementById("hom-useful-life").value = info.life; document.getElementById("hom-life-hint").textContent = info.label; } };

// Initialize on load homUpdateLife();

window.homCalc = function() { const resultDiv = document.getElementById("hom-result"); resultDiv.style.display = "block";

// --- Inputs --- const replacementCost = parseFloat(document.getElementById("hom-replacement-cost").value); const age = parseFloat(document.getElementById("hom-age").value); const usefulLife = parseFloat(document.getElementById("hom-useful-life").value); const salvagePct = parseFloat(document.getElementById("hom-salvage").value) || 0; const condition = document.getElementById("hom-condition").value; const conditionMult = homConditionMap[condition];

// --- Validation --- const errors = []; if (isNaN(replacementCost) || replacementCost 50) errors.push("Salvage value must be between 0% and 50%."); if (!isNaN(age) && !isNaN(usefulLife) && age > usefulLife * 1.5) errors.push("Age is significantly beyond useful life — verify your inputs.");

if (errors.length > 0) { resultDiv.innerHTML = "Please fix the following:" + errors.map(e => "").join("") + ""; return; }

// --- Core Formula: Straight-Line Depreciation with Salvage --- // Depreciable Base = Replacement Cost × (1 - Salvage%) // Annual Depreciation = Depreciable Base / Useful Life // Accumulated Depreciation = Annual Depreciation × min(Age, Useful Life) // Depreciated Value (before condition) = Replacement Cost - Accumulated Depreciation // Actual Cash Value (ACV) = Depreciated Value × Condition Multiplier // ACV is floored at Salvage Value

const salvageValue = replacementCost * (salvagePct / 100); const depreciableBase = replacementCost - salvageValue; const annualDepr = depreciableBase / usefulLife; const effectiveAge = Math.min(age, usefulLife); const accumulatedDepr = annualDepr * effectiveAge; const depreciatedValue = replacementCost - accumulatedDepr; const acv = Math.max(depreciatedValue * conditionMult, salvageValue); const totalDeprPct = ((replacementCost - acv) / replacementCost) * 100; const remainingLifePct = Math.max(0, ((usefulLife - age) / usefulLife) * 100); const remainingYears = Math.max(0, usefulLife - age);

// --- Percent depreciated (straight-line, before condition) --- const straightLineDeprPct = (effectiveAge / usefulLife) * 100;

const fmt = v => "$" + v.toLocaleString("en-US", {minimumFractionDigits: 2, maximumFractionDigits: 2}); const pct = v => v.toFixed(1) + "%";

const conditionLabels = { excellent: "Excellent (×1.10)", good: "Good (×1.00)", fair: "Fair (×0.85)", poor: "Poor (×0.70)" };

// Depreciation bar const deprBarWidth = Math.min(totalDeprPct, 100).toFixed(1); const barColor = totalDeprPct

Replacement Cost ${fmt(replacementCost)}

Salvage Value (${pct(salvagePct)}) ${fmt(salvageValue)}

Depreciable Base ${fmt(depreciableBase)}

Annual Depreciation ${fmt(annualDepr)} / yr

Accumulated Depreciation (${effectiveAge} yr${effectiveAge !== 1 ? "s" : ""}) ${fmt(accumulatedDepr)}

Straight-Line Depreciated Value ${fmt(depreciatedValue)}

Condition Adjustment ${conditionLabels[condition]}

Actual Cash Value (ACV) ${fmt(acv)}

Total Depreciation: ${pct(totalDeprPct)} Remaining Life: ${remainingYears.toFixed(1)} yrs (${pct(remainingLifePct)})

0% depreciated100% depreciated

Interpretation: At ${age} year${age !== 1 ? "s" : ""} of age, this system has used ${pct(straightLineDeprPct)} of its expected useful life. After condition adjustment, its estimated Actual Cash Value is ${fmt(acv)} — a total depreciation of ${fmt(replacementCost - acv)} (${pct(totalDeprPct)}) from replacement cost.

`; };

})();

#### Formula

Straight-Line Depreciation with Salvage Value & Condition Adjustment:

Condition Factors: Excellent = 1.10 | Good = 1.00 | Fair = 0.85 | Poor = 0.70

#### Assumptions & References

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