How to Do a DIY Home Energy Audit (Find Where You're Losing Money)

A professional energy audit costs $300–$600 and involves blower-door tests, thermal cameras, and combustion analysis. They're great — but most homeowners can find 80% of their energy problems in an afternoon with a candle, a flashlight, and this checklist.

Here's how.

What You're Looking For

Energy leaves your home through four paths:

1. Air leaks — gaps where outside air infiltrates or conditioned air escapes
2. Conduction — heat moving through poorly insulated walls, ceilings, floors
3. Mechanical inefficiency — HVAC systems working harder than they should
4. Behavioral waste — habits that cost money unnecessarily

This audit focuses on #1 and #2, which are responsible for the majority of residential energy waste.

Tools You Need

Free (you probably have these):

• A candle or incense stick
• Flashlight
• Smartphone (for the free tools below)

Optional but useful (~$15–$50):

Room-by-Room Audit Checklist

Step 1: Start Outside

Walk around your home's exterior on a cold day (or after dark) and look for:

• Gaps where different materials meet: brick-to-siding, siding-to-foundation, around utility penetrations (gas lines, hose bibs, dryer vents, electrical conduit)
• Damaged caulk around windows and doors — caulk that's cracked, missing, or pulling away
• Daylight visible through any gaps at doors or under garage door

Mark everything with painter's tape or take photos with your phone.

Step 2: Test Doors and Windows

On a windy day, go inside and slowly run a candle or incense stick around:

• Window frames (all four sides)
• Door frames, especially corners
• The threshold gap under exterior doors
• Sliding door tracks

Any flame flicker = air movement = heat loss.

Common findings:

• Corner joints in window frames often gap as homes settle
• The gap between door trim and rough framing is usually not sealed
• Sliding doors rarely seal well at the top track

Step 3: Check Electrical Outlets and Switches

On exterior walls, electrical outlets are notorious air leak points. The wiring chase goes through the wall, and without foam gaskets, it's an open connection to outside air.

Test: On a cold day, put your hand near an outlet on an exterior wall. Feel any coolness? That's outside air.

Fix: Foam gaskets behind the cover plate ($3 for a pack of 10).

Step 4: Inspect the Attic

The attic is where most homes lose the most energy. Check:

Insulation level: Look between the joists. If you can see the tops of the joists (typically 5.5" tall), you have R-19 or less — not enough for most climates. Target R-38 to R-60.

Attic hatch: The pull-down attic stairs are usually completely uninsulated — a 8-square-foot hole in your thermal envelope. Feel it on a cold day — it'll be cold.

Recessed lights: "Pot lights" that poke through the ceiling into the attic are major air leak points. Look for daylight around them from the attic side.

Attic bypasses: Stud cavities, plumbing chases, and chimney surrounds often connect living space directly to attic without any air barrier. These are the biggest finds of most professional audits.

Step 5: Check the Basement and Crawlspace

Rim joists (where the floor framing meets the foundation walls) are usually uninsulated and full of air gaps. On cold days, you can feel cold air blowing in at the junction of the floor and foundation wall.

Exposed foundation: If you have an uninsulated basement, that cold air permeates up through the floor.

Ductwork: Look at all duct connections in the basement or crawlspace. Gaps at connections let conditioned air escape before reaching your rooms.

Water heater and furnace flue: The area around flues is often unsealed where they penetrate through floors and ceilings.

Step 6: Inspect Your HVAC System

Filter condition: If it's gray and clogged, your system is working harder than it should. Replace every 60–90 days.

Duct condition: Look for disconnected ducts, tears in flexible ductwork, or duct joints that have separated.

Age: If your furnace is 15+ years old or your AC is 10+ years old, they're likely at 60–70% efficiency compared to modern equipment's 90–98%.

Refrigerant: If your AC seems to run constantly without cooling well, it may be low on refrigerant (call a pro for this).

Step 7: Water Heater Check

• Age: Check the serial number. After 10–12 years, efficiency drops significantly.
• Insulation: Feel the tank — if it's warm, you're losing standby heat. An insulation blanket helps.
• Temperature setting: Most ship set to 140°F. 120°F is safer and saves 5–10%.
• Pipe insulation: The first 6 feet of hot and cold pipes should be insulated.

Step 8: Lighting Audit

Walk through every room and count:

• How many bulbs are still incandescent (warm light, runs hot to the touch)?
• How many are CFL (spiral tubes)?
• How many are LED?

Incandescents use 4–5× more electricity than LEDs. A single 60W incandescent replaced with a 9W LED saves $8–$10/year. Replace all of them in an afternoon.

Compile Your Findings: Prioritizing by Impact

After your walkthrough, rank your findings:

| Priority | Finding | DIY Cost | Annual Savings | |----------|---------|---------|----------------| | 1 | Attic air sealing | $50–$150 | $150–$400 | | 2 | Window/door caulking | $20–$50 | $100–$250 | | 3 | Outlet foam gaskets | $10 | $30–$80 | | 4 | Attic insulation upgrade | $300–$700 | $150–$400 | | 5 | Rim joist insulation | $100–$200 | $75–$200 | | 6 | LED lighting | $30–$80 | $80–$200 | | 7 | Water heater temp reduction | $0 | $30–$80 |

Start with the highest impact items. The air sealing typically pays back within weeks.

Free Digital Tools to Supplement Your Audit

ENERGY STAR Home Energy Yardstick — Enter your utility bills and get an efficiency score vs. similar homes in your area.

Lawrence Berkeley National Lab Home Energy Saver — Calculates potential savings by improvement category.

Your utility company's app — Most large utilities now show usage patterns and compare you to similar homes.

When to Call a Professional

Consider a professional audit (RESNET-certified energy auditor) when:

• Your utility bills are extremely high and you can't find why
• You're planning major renovations and want to optimize before construction
• You want a blower-door test (quantifies total air leakage)
• Your home has comfort problems (one room always too hot or cold)
• You're applying for rebates that require a professional audit

Many state programs offer subsidized or free professional audits for income-qualifying households.

How Much Can You Save?

Studies show DIY audits followed by self-implemented fixes average 10–30% bill reductions. Professional audit + recommended fixes often reach 20–40%.

The real value of an audit isn't the savings on any one item — it's knowing which items to prioritize. Without an audit, many homeowners spend money on flashy upgrades (new windows, solar) while ignoring the air sealing that would pay back in months.

Start with the free checklist above. You'll likely find enough problems to keep you busy for a few weekends — and see the savings on your very next bill.