Weatherization improves a home’s thermal boundary with insulation, air sealing, duct sealing, and draft control. ENERGY STAR estimates that cost-effective air sealing and insulation save about 15% of heating and cooling costs—or 11% of total energy costs—on average for modeled typical existing U.S. homes; enter your bill below for a home-specific planning range.
Last reviewedJuly 18, 2026
Core methodGuided load-reduction ranges by home, climate, and project
Benchmark15% of HVAC costs is different from 11% of total energy costs
PrivacyNo server upload or input tracking
Quick Answer
Use heating and cooling spending when possible. The ENERGY STAR U.S. benchmark is an average 15% of heating and cooling costs, or an average 11% of total energy costs, for a specific cost-effective air-sealing and insulation package—not two percentages that can be applied to the same bill.
Fastest estimateEnter a bill, climate, home condition, planned projects, and installed costs.
Results you getA three-scenario range, ranked projects, payback, ROI, lifetime value, and NPV.
Safety limitMajor air sealing can require ventilation, combustion safety, moisture, and radon checks.
Build your estimate
Guided mode estimates a range from your home and project choices. Switch to audit results only when you have measure-specific reduction percentages.
Results
Complete the five short steps, then calculate.
Worked example: attic insulation plus air sealing
A mixed-climate 1,800 ft² home spends $1,800 per year on heating and cooling. An audit estimates 6% savings from attic insulation and 7% from whole-home air sealing. Installed costs are $2,400 and $900; a verified $500 rebate is assigned to insulation.
The arithmetic uses heating and cooling spending because weatherization does not normally reduce appliance loads, water heating, taxes, or fixed utility charges. Comfort and resilience benefits are also omitted.
How the estimate works
Guided mode assigns a conservative, typical, and optimistic load-reduction range to each selected project, then adjusts it for climate severity, home age and condition, HVAC efficiency, attic condition, and—when entered—insulation R-value improvement and affected area. The ranges are planning heuristics calibrated around the ENERGY STAR whole-package benchmark, not simulations of the building.
Annual HVAC cost = bill × (12 when monthly) × (HVAC share when using a total bill)Combined savings = [1 − (1 − project 1) × (1 − project 2) × …] × (1 − overlap)Example: 7%, 5%, and 2% projects with 10% overlap = [1 − 0.93 × 0.95 × 0.98] × 0.90 = 12.1%Annual savings = annual HVAC cost × combined savingsSimple payback = net project cost ÷ first-year net savingsNPV = −net cost + Σ[(year-one savings × (1 + escalation)^(year−1) − maintenance) ÷ (1 + discount)^year]
Planning limit: tightening a home can affect ventilation, moisture, radon, fireplaces, combustion appliances, and indoor air quality. Use qualified help for blower-door testing, combustion-safety checks, and code-required ventilation. Savings can also be reduced by installation defects, behavior changes, rebound effects, or weather that differs from the assumed climate.
Assumptions, sources, and trust signals
Method authored by the Starlight Tools editorial team and technically reviewed against the official sources below on July 18, 2026. No contractor, utility, government agency, or product manufacturer reviewed or endorsed this calculator.
Direct combustion planning factors; upstream emissions excluded
Financial defaults
15 years; 2% escalation; 3% discount; 10% overlap
Starlight Tools transparent planning assumptions, not forecasts
Model version July 18, 2026
Editable; escalation is nominal and discounting produces present-value dollars
Great Britain / EU rate presets
Rounded values loaded when selected
Starlight Tools illustrative mid-2026 planning inputs, explicitly not official averages
Model version July 18, 2026
Use only as placeholders; replace with supplier tariffs, official national fuel conversions, and national grid factors
Replace estimates with better evidence
Use a utility bill analysis for the cost basis, a blower-door test for leakage, an audit model for measure reductions, contractor quotes for installed costs, program award documents for incentives, and your utility tariff and regional eGRID factor for rates and emissions. The model does not assess moisture assemblies, asbestos, knob-and-tube wiring, radon, ventilation, or combustion safety.
FAQs
How much does weatherization typically save?
ENERGY STAR reports average savings of about 15% on heating and cooling costs, or 11% on total energy costs, for modeled cost-effective air sealing and insulation in typical existing U.S. homes. Those percentages use different cost bases and are benchmarks, not guarantees.
Should insulation or air sealing come first?
An assessment usually identifies and seals major leaks before insulation is added, especially in an attic, because insulation can hide leakage paths. Combustion-safety, moisture, radon, and ventilation needs should be checked before major tightening.
How do home age and climate affect savings?
Older, leakier, under-insulated homes and homes in more severe climates generally have more opportunity, while already efficient homes usually have less. Actual results also depend on fuel, equipment, behavior, and installation quality.
What does R-value mean?
R-value measures resistance to heat flow; a higher value generally insulates better. Recommended assemblies vary by climate, location in the building, material, and local code.
Do I need an energy audit or blower-door test?
Not for an early planning estimate, but an audit and blower-door test can locate leaks, quantify air leakage, improve savings assumptions, and identify safety or ventilation work before installation.
What projects count as weatherization?
Common projects include attic, wall, floor, crawl-space, and rim-joist insulation; whole-home and duct air sealing; weatherstripping; draft control; and sometimes storm windows or window improvements.
Why can windows have a longer energy-only payback?
Full window replacement is often expensive relative to the energy it saves when lower-cost sealing or insulation opportunities remain. Windows may still provide meaningful comfort, noise, durability, or maintenance benefits not counted here.
Can renters use this estimate?
Yes, for planning portable or landlord-approved measures. Renters should obtain permission before altering the building and should enter only costs and bill savings they expect to bear.
How do rebates affect payback?
Verified rebates, grants, and credits reduce net cost and usually shorten homeowner payback. Programs, funding, tax eligibility, and contractor requirements change, so verify every incentive with the administering agency before relying on it.