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Free green roof energy savings calculator for annual cooling cost baselines, expected percent cooling savings, vegetated area for $/ft² reporting, and optional installed cost simple payback. Pair with green building and envelope tools for a fuller retrofit story.
Last updated: April 18, 2026
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Used for savings per ft²; savings still scale from your cooling cost and percent.
Portion of cooling spend a green roof can influence (building-level or roof-attributed).
Annual savings
$672
$56.00 / month · $0.269 / ft² / yr
Cooling cost after: $4,128 / yr
Simple payback
141.37 years
5-year cumulative
$3,360
10-year cumulative
$6,720
Planning note
Mechanism
Less heat into deck
Your percent captures the net modeled or estimated effect.
Climate
Hot summers benefit most
Irrigation and plant health affect performance.
Design
Often bundled with roof work
Fold extra R-value into your percent or baseline if modeled separately.
Externalities
Not priced here
City-scale cooling benefits are outside this building-level calculator.
Stack measures
Air seal and insulation
Combine with weatherization screening.
Life cycle
Membrane protection
Stormwater and longevity benefits are not monetized in energy outputs.
2,500 ft² roof, $4,800 cooling baseline, 14% savings, $95k project:
Annual savings
$672
Simple payback
141.4 yrs
$/ft² / yr
$0.27
Annual energy savings equal your cooling cost baseline times the percent cooling energy saved. Remaining cooling cost is baseline minus savings. Savings per square foot divides annual savings by vegetated roof area. Simple payback divides installed cost by annual savings when both are positive.
annual_savings = cooling_baseline × (percent / 100)savings_per_ft² = annual_savings / roof_areapayback = project_cost / annual_savingsGrowing media, drainage, and waterproofing define real assemblies
See broader impacts in our green building savings calculator.
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