Window Replacement ROI Calculator

Calculate window replacement return on investment including annual savings, payback period, and 20-year net savings.

Inputs

Number of Windows

Old Window U-Factor

New Window U-Factor

Avg Window Area

sq ft

Energy Cost per BTU

Cost per Window

Heating Degree Days

Cooling Degree Days

Tab to move between fields

Results

Annual Energy Savings

$222.75

≈ 15 movie tickets

Payback Period

53.9 years

20-Year Net Savings

-$7,545.00

Total Replacement Cost$12,000.00

20-Year ROI-62.87%

How to Use This Calculator

Enter the Number of Windows and Average Window Area in sq ft for all replacements.
Enter the Old Window U-Factor and New Window U-Factor to quantify the thermal improvement.
Enter Energy Cost Per BTU, Replacement Cost Per Window, and local Heating and Cooling Degree Days.
Review Annual Energy Savings and Total Replacement Cost.
Check Payback Period in years, 20-Year Net Savings, and 20-Year ROI to evaluate the investment.

How the result changes with Old Window U-Factor

Old Window U-Factor	Annual Energy Savings	Payback Period	20-Year Net Savings
0.33	$71.28	168.4 years	-$10,574.40
0.66	$360.86	33.3 years	-$4,782.80
1.05	$712.80	16.8 years	$2,256.00
1.37	$997.92	12 years	$7,958.40

What each input means

Number of Windows: Total number of windows being replaced.
Old Window U-Factor: U-factor of existing windows (single pane ~1.0, old double ~0.5).
New Window U-Factor: U-factor of replacement windows (Energy Star ~0.25-0.30).
Avg Window Area: Average area of each window.
Energy Cost per BTU: Cost per BTU of heating/cooling energy (~$0.00003 for natural gas).
Cost per Window: Installed cost per replacement window.
Heating Degree Days: Annual heating degree days for your location (base 65°F).
Cooling Degree Days: Annual cooling degree days for your location (base 65°F).

How this is calculated

Worked example, using the default values

Identify Input Parameters
4 parameters
Number of Windows = 15, Old Window U-Factor = 0.5, New Window U-Factor = 0.25, Avg Window Area = 15 = 8 input(s) provided
Calculate Annual Energy Savings
Annual Energy Savings
222.75 = $222.75
Calculate Payback Period
Payback Period
53.9 = 53.9
Calculate 20-Year Net Savings
20-Year Net Savings
-7545 = $-7,545
Calculate Total Replacement Cost
Total Replacement Cost
12000 = $12,000
Calculate 20-Year ROI
20-Year ROI
-62.87 = -62.87

Engine last updated July 28, 2026. Checked against 3 independently-derived tests — how we verify calculators.

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