Window Repair vs Replacement Cost Calculator
Compare the total cost of repairing your existing windows versus replacing them, factoring in energy savings, lifespan, and maintenance over time.
Formulas Used
Adjusted Repair Cost per Window:
Adj. Repair Cost = Repair Cost × Damage Multiplier
(Minor = 1.0×, Moderate = 1.6×, Severe = 2.8×)
Present Value of Annuity (maintenance / energy savings):
PV = A × [1 − (1 + r)^(−n)] / r
where A = annual amount, r = discount rate, n = years
Total Net Present Cost — Repair:
Totalrepair = (Adj. Repair Cost × N) + PV(Maintenancerepair) + PV(Mid-Period Replacement, if needed)
Total Net Present Cost — Replacement:
Totalreplace = (Replace Cost × Type Multiplier × N) + PV(Maintenancereplace) − PV(Energy Savings)
Annual Energy Savings:
Savings = Annual Energy Bill × (Energy Savings % / 100)
Simple Payback Period:
Payback = (Replace Upfront − Repair Upfront) / (Annual Energy Savings − Annual Maintenance Difference)
Remaining Life After Repair:
Remaining Life = (Window Lifespan − Current Age) × Repair Life Extension Factor
(Minor = 80%, Moderate = 50%, Severe = 25%)
Assumptions & References
- Repair cost multipliers by damage level are based on typical contractor pricing ranges (HomeAdvisor, Angi 2023–2024).
- Window type cost multipliers: Single-Pane (0.75×), Double-Pane (1.0× baseline), Triple-Pane (1.35×), Bay/Picture (2.2×) — sourced from Modernize and HomeGuide national averages.
- Annual maintenance cost assumed at 5% of repair cost for repaired windows and 1% of replacement cost for new windows.
- Energy savings of 10–15% are typical for upgrading from single- to double-pane; up to 25–30% for triple-pane (U.S. DOE Energy Saver).
- Window lifespans: Single-Pane ~15 yrs, Double-Pane ~20 yrs, Triple-Pane ~25 yrs, Bay/Picture ~20 yrs (NAHB, 2021).
- Discount rate represents the opportunity cost of capital or expected inflation; 3% is a common real discount rate for home improvement analysis.
- If repaired windows are expected to fail before the analysis period ends, a mid-period full replacement is included in the repair scenario cost.
- Costs are national U.S. averages; local labor and material costs may vary significantly.
- Tax credits or rebates (e.g., IRS Energy Efficient Home Improvement Credit — up to 30% of replacement cost) are not included but may further favor replacement.