How to Do a Home Energy Audit Yourself, Room by Room

Your energy bill tells you how much you spent. It doesn’t tell you where the money went. Is it the drafty back door, the thin attic insulation, the old fridge in the garage or the gaming PC that never sleeps?

A home energy audit answers that question. Professionals use blower doors and infrared cameras, and they’re worth hiring for big decisions. But you can find many of the easiest, cheapest fixes yourself in an afternoon with a flashlight, an incense stick and a couple of inexpensive gadgets.

This guide walks you through a DIY audit room by room, the tools that help, and what to fix first.

Why a DIY audit is worth an afternoon

The payoff from fixing the basics can be real. ENERGY STAR estimates homeowners can save an average of 15% on heating and cooling costs, or about 11% of total energy costs, by air sealing and adding insulation in attics, floors over crawl spaces and accessible basement rim joists. ENERGY STAR also says about 9 in 10 U.S. homes are under-insulated.

The U.S. Department of Energy (DOE) is clear that a DIY walk-through isn’t as thorough as a professional assessment. But it helps you spot the obvious problems, decide what to fix yourself and know what to ask a contractor about.

Tools you’ll need

You don’t need much. Here’s a practical toolkit, from free to moderately priced.

A thermal camera is the most useful upgrade. It shows temperature differences as colors, so a missing patch of insulation or a leaky window frame shows up clearly. It works best when there’s a big temperature difference between inside and outside, such as a cold winter morning.

Key takeaway: Start with free tools and your utility bills. A thermal camera and a few energy-monitoring smart plugs turn guesses into evidence for very little money.

Step 1: Start with your bills

Before you walk the house, pull up 12 months of electric and gas bills or your utility’s online usage dashboard. Look for:

• Seasonal swings. Big winter or summer spikes point to heating, cooling and the building envelope.
• A high baseline. If usage stays high in mild spring and fall months, look at always-on devices, water heating, old appliances and pool pumps.
• Sudden jumps. A month that’s much higher than the same month last year can mean failing equipment, a new appliance or a rate change.

If your bills keep rising even when usage doesn’t, our guide to why electricity bills are rising explains the rate side.

Step 2: Hunt for air leaks, room by room

Air leaks are usually the cheapest problem to fix. DOE recommends a careful walk-through looking at the places where leaks usually hide.

Where to look

• Exterior walls and trim: around electrical outlets, switch plates, baseboards and crown molding.
• Windows and doors: frames, sills, weatherstripping and door sweeps.
• Where materials meet: between the foundation and walls, between chimney and siding.
• Penetrations: where pipes, cables, phone and TV lines, dryer vents, gas lines and electrical service enter the home.
• Attic hatch or pull-down stairs: a common, easy-to-fix leak.
• Window or wall air conditioners left in place year-round.
• Fireplace: check that the damper closes tightly.

How to find leaks

DOE describes a simple depressurization test, best done on a cool, windy day:

1. Close all exterior doors, windows and fireplace flues.
2. Turn off combustion appliances such as gas furnaces and water heaters (DOE notes you can skip this if you don’t want to turn off the furnace).
3. Turn on all exhaust fans that blow outside, such as bathroom fans and the range hood.
4. Pass a lit incense stick or smoke pencil along common leak areas. If the smoke is pulled sideways or blown into the room, you’ve found a leak.

Two other DOE-recommended tricks: have a helper shine a flashlight around door and window edges at night while you watch from outside for light, and close a door or window on a sheet of paper. If it slides out without tearing, the seal is weak.

Safety first: turn everything back on afterward, never leave incense unattended, and make sure you have working carbon monoxide alarms if you have any gas, oil or wood-burning appliances.

Step 3: Check insulation in the attic, walls and basement

Attic

The attic is usually the best place to start. Look at the insulation depth with a ruler. If you can see the tops of the floor joists, you probably need more. Check that the insulation covers the whole floor evenly, with no bare spots, and that the attic hatch is insulated and weatherstripped like the rest of the attic.

Also look for gaps around plumbing vent pipes, chimneys, recessed lights and wiring holes. These should be sealed before adding insulation.

Walls

Walls are harder to check. A thermal camera on a cold day can reveal cold stripes or patches where insulation is missing or has settled. Without one, you can turn off power to an outlet on an exterior wall, remove the cover and look carefully with a flashlight. Don’t poke anything into the box.

Basement and crawl space

Look at the rim joists (where the floor framing sits on the foundation), which are common leak and insulation gaps. Check whether pipes and ducts running through unheated spaces are insulated.

Step 4: Inspect heating, cooling and ducts

• Filters: Check forced-air filters and replace them on the manufacturer’s schedule. A clogged filter makes the system work harder.
• Equipment age and maintenance: Note the age of your furnace, heat pump, AC and water heater, and when they were last serviced. Annual professional maintenance is common advice.
• Ducts: In the attic, basement or crawl space, look for disconnected sections, gaps at seams and missing insulation. Seal gaps with mastic or foil tape, not standard cloth duct tape.
• Thermostat: If you still use a manual thermostat and often forget to adjust it, read our guide on whether smart thermostats save money.
• Water heater: Check the temperature setting and look for leaks or corrosion.

If your furnace or AC is near the end of its life, our heat pump vs furnace comparison can help you plan the replacement.

Step 5: Measure plug loads and appliances

This is where smart plugs and plug-in meters shine. Plug a device into the meter for a day or a week and you’ll see exactly how much energy it uses.

Focus on:

• Always-on electronics: TVs, game consoles, cable and streaming boxes, desktop computers, printers and chargers. Many draw power even when “off.” Research from Lawrence Berkeley National Laboratory has found standby power can be a noticeable share of household electricity use, varying widely from home to home.
• Second fridges and freezers, especially older ones in a garage.
• Dehumidifiers, space heaters and pool or spa pumps.
• Lighting: Replace any remaining incandescent or halogen bulbs with LEDs.

Fixes are simple: put entertainment systems on a smart power strip, enable sleep settings and retire the old garage fridge if it’s barely used. If you’re adding smart plugs anyway, our guide to setting up a smart home covers scheduling and automations.

If you’re also weighing kitchen upgrades, see our comparison of induction vs gas stoves.

What to fix first

Prioritize by cost and impact:

1. Air seal the attic floor, attic hatch, rim joists and around doors and windows. Caulk, weatherstripping, door sweeps and spray foam for larger gaps are inexpensive DIY materials.
2. Add attic insulation if it’s thin or uneven. Many homeowners do this themselves, but hire a pro if you have old vermiculite insulation, which may contain asbestos, or knob-and-tube wiring.
3. Seal and insulate accessible ducts in unconditioned spaces.
4. Cut plug loads with smart strips, settings changes and LED bulbs.
5. Plan bigger upgrades such as new windows, wall insulation or HVAC replacement after a professional assessment.

When to call a professional

DOE describes professional assessments as equipment-based, usually using a calibrated blower door to measure how airtight the house is and an infrared scan to find leaks. Assessors may also check heating and cooling systems, test for gas leaks and check ventilation. DOE’s consumer guide puts the cost at roughly $250 to $600 or more, and notes many contractors reduce the price if you hire them for the upgrades. Your utility or state energy office may offer free or discounted assessments, and DOE’s Weatherization Assistance Program helps eligible low-income households.

Call a pro if you smell gas, see signs of moisture or mold, have combustion appliances and plan major air sealing (tight homes need proper ventilation), or are planning a large investment.

A note on taxes: the federal Energy Efficient Home Improvement Credit (Section 25C), which helped pay for some audits and upgrades, has ended. The IRS says it is not allowed for property placed in service after December 31, 2025, following the July 2025 budget law. Check your utility and state for current rebates. This is not legal or tax advice.

The bottom line

A DIY home energy audit takes an afternoon and a few cheap tools, and it often finds the fixes with the fastest payback: air leaks, thin attic insulation, leaky ducts and always-on electronics. Start with your bills, walk the house room by room, measure what you can and fix the cheap things first. Save the professional assessment for the big decisions. For terms like R-value and blower door, see our tech glossary.

Sources

• U.S. Department of Energy: Consumer guide to home energy assessments — DIY walk-through, depressurization test, flashlight and paper tests, professional blower door and infrared methods, cost range
• ENERGY STAR: Why seal and insulate — average 15% heating and cooling savings, 11% total energy savings, share of under-insulated homes
• Lawrence Berkeley National Laboratory: Whole-house measurements of standby power consumption — standby power as a share of household electricity
• IRS: FAQs on modifications to sections 25C, 25D and other energy credits under Public Law 119-21 — end of the 25C credit after December 31, 2025