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Window Film Retrofit Payback Calculator
Window film cuts solar heat gain and extends HVAC life for fraction of new window cost.
Payback years
17.1
Annual savings
$4,200
Net investment
$72,000
How the math works
Investment = sqft × cost − rebate. Savings = kWh × rate. Payback = investment / savings.
8k × $10 − 8k × $1 = $72k. 35k × $0.12 = $4,200. 17.1 years — long.
How to Use
- Enter window sqft.
- Enter film cost per sqft.
- Enter cooling energy saved kWh.
- Enter electricity rate.
- Enter HVAC life extension years.
- Read payback.
Frequently Asked Questions
Window film benefits?
Solar heat gain reduction: 25-75% depending on film grade. UV rejection: 99% (prevents fade + skin damage). Glare reduction: improves tenant comfort. Heat loss (low-e film): 30-50% winter U-value improvement. Security film: holds broken glass together, 4-5× break-resistance. Cost: $6-20/sqft installed. Life: 10-20 years.
Energy savings?
Cooling energy reduction: 10-25% in south/west-facing buildings with heavy solar gain. On $100k annual cooling spend: $10-25k savings. Peak demand reduction: 15-30% during summer peaks. Reduces HVAC equipment sizing if replaced at end of life (capex saving). Typical payback: 3-8 years on solar film. Shorter in hot climates (TX, FL, AZ).
Window replacement alternative?
New double-pane low-e windows: $40-80/sqft installed (commercial). 5-10× cost of window film. Payback: 15-25+ years on energy alone. Full window replacement justified when: (1) Windows at end of life, (2) Historic preservation requires it, (3) Aesthetic concern (original windows ugly), (4) Condensation/air leak issues. Otherwise: window film preferred for energy retrofit.
Utility rebates?
Some utilities offer prescriptive window film rebates: $1-4/sqft. Limited geographic availability. Energy efficiency programs (CEE, DSIRE databases) document current rebates. Pair with Energy Star or LEED certification: additional value stack. Commercial building deduction 179D: solar film counts toward energy reduction threshold ($0.30-2/sqft deduction).
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