How Much Do Leaky Ducts Cost You? (2026 Math)

Key Takeaways

Common Question	Short Answer
How much energy do leaky ducts waste?	ENERGY STAR estimates that a typical home loses 20–30% of the air moving through its ducts. On a $1,800 annual heating and cooling bill, 25% leakage is up to about $450 a year. Lower energy bills
How much can duct sealing lower my energy bill?	It depends on how leaky your ducts are and where they run. With typical losses of 20–30%, the waste on a $1,800 bill can be roughly $360–$540 a year, and MaxSeal’s average leakage reduction is 86%. See the results study
Is duct sealing worth it?	Usually yes, when a leakage test shows significant leakage. At $3,000–$3,500 per system, energy payback is roughly 5–9 years for homes wasting $450–$720 a year. Is Aeroseal worth it?
Will a new high-efficiency HVAC system fix high bills?	Not if the ducts leak. The new equipment’s air still escapes before it reaches your rooms, so test and seal the ducts first. Fix ducts before replacing HVAC
Does sealing ducts reduce HVAC runtime?	Yes. More air reaches the rooms each minute, so the system satisfies the thermostat sooner. A 38% airflow gain works out to roughly 28% less runtime in theory.
How do I find out how leaky my ducts are?	Get a duct leakage test. At MaxSeal it starts at $295. Duct leakage test
Is there a tax credit for duct sealing in 2026?	The federal 25C credit ended for improvements placed in service after December 31, 2025. BayREN’s EASE Home program covers duct sealing for income-qualified Bay Area homes. Tax credits in 2026

1. Why leaky ducts waste so much

Your furnace or AC conditions air, and your ducts deliver it. Every leak means you pay to heat or cool air that ends up in the attic, crawl space, garage or wall cavities instead of your rooms. Return-side leaks make it worse by pulling in hot attic air in summer or cold crawl-space air in winter, which the system then has to condition again.

2. Estimate what leakage costs you

Formula: Annual heating + cooling spend × leakage share = estimated annual waste

Annual heating + cooling spend	15% leakage	25% leakage	40% leakage
$1,000	$150	$250	$400
$1,800	$270	$450	$720
$2,500	$375	$625	$1,000
$3,500	$525	$875	$1,400

Treat this as an upper estimate. Some leaked air ends up inside the house and isn’t fully wasted. Leaks in the attic or crawl space waste the most.

3. Understand the runtime effect

When more air reaches your rooms each minute, the thermostat is satisfied sooner.

Runtime reduction ≈ 1 − (airflow before ÷ airflow after)

Airflow gain at registers	Theoretical runtime reduction
+10%	9%
+20%	17%
+33%	25%
+38% (MaxSeal median, 38 systems)	28%
+47% (MaxSeal average, 38 systems)	32%
+64% (MaxSeal average, high-leakage homes)	39%

Less runtime means less electricity and gas, less wear on the blower and compressor, and fewer on/off cycles. Real savings depend on climate, thermostat habits, insulation and equipment, so treat these numbers as ranges, not promises.

4. Compare the payback

	Seal the ducts	Upgrade to a high-efficiency furnace or AC (keep leaky ducts)
Fixes air lost before it reaches rooms	Yes	No
Improves room-to-room comfort	Yes	Rarely
Typical cost	MaxSeal: $3,000–$3,500 per system	Usually much higher
Makes a future equipment upgrade work better	Yes	—

Simple energy payback at MaxSeal prices

Assumes sealing recovers 86% of the waste (MaxSeal’s average leakage reduction).

Estimated annual duct waste	Recovered per year	Payback at $3,000	Payback at $3,500
$270	~$232	~13 years	~15 years
$450	~$387	~8 years	~9 years
$720	~$619	~5 years	~6 years
$1,000	~$860	~3.5 years	~4 years

Energy is only part of the return. Comfort in starved rooms, less dust and less wear on equipment don’t show up in this table.

A 97% efficient furnace connected to ducts that lose 30% of their air is no longer delivering anything close to 97% of its heat to your rooms. Sealing first protects any equipment investment.

5. What affects your real savings

Where the ducts run. Ducts in attics, crawl spaces and garages waste more energy than ducts inside conditioned space.
Your starting leakage. Bigger leaks mean bigger savings. In MaxSeal’s data, high-leakage systems gained +64% airflow, compared with +36% for moderate ones.
Climate and usage. Hot Bay Area inland summers and heavy AC use increase the payoff.
Insulation. Sealed ducts in a hot attic should also be insulated.

6. Are there tax credits or rebates for duct sealing in 2026?

The federal Energy Efficient Home Improvement Credit (25C), which covered air sealing, was ended by the One Big Beautiful Bill Act for improvements placed in service after December 31, 2025. Work completed in 2025 could still qualify on your 2025 return, for 30% of the materials cost only. For 2026 work, BayREN’s EASE Home program covers duct sealing for income-qualified Bay Area homes. See what still applies in 2026, and confirm with a tax professional.

Conclusion

Leaky ducts can waste a real share of what you spend on heating and cooling, and they make your system run longer to deliver the same air. The formula and tables above give you a rough upper estimate of your own waste.

Real savings depend on where your ducts run, how leaky they are, your climate and your equipment. A leakage test turns the estimate into a number for your home.

Get a Free Consultation or call (408) 400-3630.