The numbers
A typical drafty exterior door has gaps totaling 4-8 square inches of effective leak area (visible daylight, rattling, or a draft you can feel). At a 30°F indoor-outdoor difference running 16 hours/day for 180 heating days, that's roughly:
- Gas heat: $30-$60/year per door.
- Heat pump: $40-$80/year per door.
- Propane or electric resistance: $80-$160/year per door.
Most homes have 2-3 exterior doors, so the whole-house cost runs $100-$400/year for a problem that fixes for $20-$30.
Where the leaks come from
- Bottom gap: threshold worn down or door sweep missing/curled. Often the worst leak.
- Sides and top: compression weatherstripping crushed flat or torn.
- Latch side: door isn't pulled tight against the stop — adjust the strike plate.
- Around the frame: caulking shrunk or missing where the frame meets siding/drywall.
The under-$30 fix
- Add a sweep with a flexible bristle or rubber blade ($10-$15).
- Replace perimeter weatherstripping with V-strip or Q-Lon ($8-$15).
- Caulk the frame-to-wall joint inside and out ($5).
Total time: about 30 minutes per door. Total cost: typically under $30.
When to replace instead
Replace if the slab is visibly warped, the threshold is rotted, or you've already replaced weatherstripping more than twice. A modern insulated entry door is R-5 to R-7 (vs R-2 for older solid wood) and includes integrated sweeps.
Try the calculator
Drafty Window Cost Calculator
See what a single leaky window costs you each winter.
DIY safety & liability notice
This guide is for general information only. Any work you do on your home is at your own risk. Energy Savings Toolkit is not responsible for improper installation, property damage, or injury. Follow product instructions and local codes, and hire a licensed professional for electrical, gas, HVAC, roofing, or structural work. See our Disclaimer.
Next step