Every home leaks energy. The question isn’t whether yours does — it’s where, how much, and whether you know about it.
A professional home energy audit costs $150-400 and produces a detailed report of energy losses, recommended improvements, and estimated savings. It’s worth doing if you want comprehensive analysis and access to utility rebate programs that often require professional audits.
But a DIY energy audit — done in an afternoon with tools you probably already own — catches 80-90% of what a professional audit would find. The savings available from what a DIY audit reveals are often significant and the cost is essentially zero.
This guide walks you through a complete DIY home energy audit: what to look for, how to find it, what it means, and what to do about it. The strategies connect directly to the broader utility savings from our save money on utilities and save money on your electric bill guides — but where those guides tell you what to do, this one tells you where to look first.
What You Need
A DIY energy audit requires almost no special equipment:
- A candle or incense stick (for draft detection)
- A flashlight
- Your hand (for feeling temperature differences and air movement)
- Your utility bills for the past 12 months
- A notepad to record findings
Optional but useful:
- A non-contact infrared thermometer ($15-25) — identifies cold spots in walls, gaps around windows, and insulation deficiencies
- A plug-in electricity usage meter (Kill A Watt, ~$25) — measures how much power individual appliances and devices draw
- A thermal leak detector ($20-30) — more sensitive than a candle for finding air leaks
Professional thermal imaging cameras ($200-500+) are not necessary for a basic audit — the candle and your hand find the same drafts.
Part 1: Review Your Utility Bills First
Before touching anything in your home, spend 15 minutes reviewing your utility bills. This baseline tells you what you’re actually spending and helps you prioritize where to focus.
What to look for:
Month-over-month patterns: Do bills spike in winter heating months? Summer cooling months? Both? A dramatic spike in specific months points to heating or cooling efficiency as the priority area.
Year-over-year comparison: Is your usage increasing even though your household size and habits haven’t changed? Gradual increases can indicate equipment becoming less efficient, insulation degrading, or developing leaks.
Usage per degree day: Energy bills from most utilities show usage in kWh or therms. Dividing your usage by the number of “heating degree days” or “cooling degree days” (available from weather data sources) gives a normalized measure that lets you compare equivalent periods — useful for tracking whether improvements are actually reducing consumption.
Anomalies: A single month dramatically higher than expected is sometimes a billing error, sometimes a leak (especially on water bills), and sometimes equipment failure. Worth investigating.
THRIFTY HABIT #158 Create a simple spreadsheet tracking your monthly utility costs for each service across a rolling 24 months. Patterns that are invisible in month-to-month comparison become obvious across two years of data. Seasonal baselines, year-over-year trends, and the impact of efficiency improvements all show up clearly in this format.
Part 2: The Air Leak Hunt
Air leaks — gaps and cracks that let conditioned air out and outside air in — are responsible for 25-40% of home heating and cooling costs in many homes. Finding and sealing them is among the highest-return home efficiency improvements available.
The Candle Test
Light a candle or incense stick and move it slowly around the edges of:
- All exterior doors (especially along the bottom and at the frame corners)
- All windows (along the frame where it meets the wall, and where the sashes meet each other)
- Electrical outlets and light switches on exterior walls
- Where walls meet the floor and ceiling
- Around any pipes or cables that enter through exterior walls
- Attic hatch or pull-down stair
The flame or smoke will bend, flicker, or move toward or away from any air leak. Mark every location where you detect movement.
The hand test: On a cold windy day, you can feel significant drafts with your hand. Less sensitive than a candle but requires no flame near curtains or other materials.
The Common Culprits
Under exterior doors: The most frequent and significant draft source in most homes. If you can see daylight under your exterior door when it’s closed, you’re losing meaningful amounts of conditioned air. Door sweeps ($5-15) and weatherstripping replacement ($5-10) seal this quickly.
Window frames: Where the window frame meets the surrounding wall is often poorly sealed, particularly in older homes where caulk has dried and cracked. Look for gaps, cracked caulk, and places where the window frame separates from the wall.
Electrical outlets on exterior walls: Behind the outlet cover plate is often a gap directly into the wall cavity — which connects to outside air. Foam outlet insulators ($3-5 for a pack) fit behind the cover plate and seal this surprisingly significant air path.
Attic access hatches: Attic hatches are rarely insulated or well-sealed, creating a direct path for heated air to flow into the attic (in winter) or hot attic air into the living space (in summer). Adding weatherstripping around the hatch frame and insulation to the hatch itself is a worthwhile DIY improvement.
Plumbing and wiring penetrations: Anywhere a pipe, cable, or wire enters through an exterior wall is a potential air gap. Look behind the washing machine, under the kitchen sink, around the dryer vent, and anywhere else utilities penetrate exterior walls. Expanding foam sealant ($5-8 a can) fills these gaps permanently.
Fireplace dampers: When not in use, a fireplace without a closed damper is essentially an open hole in your roof. Confirm your damper closes fully and seals well. Chimney balloon inserts ($25-50) seal the flue when the fireplace isn’t being used, significantly reducing air exchange through the chimney.
Part 3: Insulation Assessment
Insulation is what keeps conditioned air inside — poor insulation means your heating and cooling systems work harder to maintain temperature, directly increasing your energy bills.
Attic Insulation Check
The attic is where most homes lose the most heat — because heat rises and escapes through the ceiling into the attic. It’s also the easiest place to add insulation because it’s accessible and the insulation just lies on the attic floor.
How to check: Go into your attic (or look through the access hatch with a flashlight) and look at the insulation on the attic floor. Current recommendations call for R-38 to R-60 depending on your climate zone — that’s roughly 12-20 inches of blown-in insulation or equivalent.
If you can see or feel the floor joists clearly through the insulation, you’re significantly under-insulated. Joists should be completely buried under insulation.
What it costs to fix: Adding blown-in attic insulation can be DIY (rental blowing machines are available at home improvement stores) or professionally installed. Typical cost: $1,500-3,000 professionally, $500-1,000 DIY. The energy savings often recoup this within 3-5 years.
Wall Insulation Check
Wall insulation is harder to assess without opening the wall — and harder to fix without significant renovation. A few indirect indicators:
Temperature of interior wall surfaces: On a cold day, hold your hand against interior walls on the side of the house facing the prevailing wind. Properly insulated walls feel close to room temperature. Poorly insulated walls feel noticeably cold to the touch.
Infrared thermometer check: An infrared thermometer pointed at wall surfaces reveals cold spots that indicate either missing insulation or significant thermal bridging through wall studs. Compare temperatures across the surface of exterior walls — cold spots that don’t align with known thermal bridges (windows, doors) may indicate insulation voids.
The outlet test: Remove the cover plate from an outlet on an exterior wall and carefully feel (or look with a flashlight) behind the electrical box. You should see insulation. Empty stud bays feel noticeably cold and confirm missing wall insulation.
Crawl Space and Basement Insulation
If your home has a crawl space or unheated basement, the floor above it should be insulated to prevent heat loss from living spaces above.
Look up at the underside of the floor from the crawl space or basement. Insulation should be visible between joists. Missing or incomplete insulation allows floor surfaces to be cold (uncomfortable) and increases heating costs.
Part 4: Heating and Cooling System Assessment
Your HVAC system’s efficiency directly affects energy costs. Several assessment points require no professional equipment.
Filter Inspection
A clogged air filter restricts airflow, making your HVAC system work harder and use more energy to move the same amount of air. Check your filter monthly — it should be replaced every 1-3 months depending on your household.
Pull the filter out and hold it up to light. A filter you can see through easily still has life. A filter that blocks most light is restricting airflow and should be replaced.
Duct Inspection (for Forced Air Systems)
Duct leaks can waste 20-30% of the conditioned air your system produces — air that escapes into walls, ceilings, and unconditioned spaces before reaching the rooms you’re trying to heat or cool.
Inspect accessible duct sections (typically in basements, crawl spaces, and attics) for:
- Disconnected sections — ducts that have separated at joints
- Visible holes or tears
- Poorly sealed connections where sections join
- Flexible duct that has crimped or collapsed
Run your system and feel along duct runs for air escaping at connections. Mastic sealant (not regular duct tape, which fails within a few years) seals duct leaks permanently and is available at hardware stores.
Thermostat Assessment
Is your thermostat programmable? A programmable or smart thermostat that reduces heating and cooling when you’re asleep or away saves 10% on annual HVAC costs — as covered in our cheapest ways to heat your home guide. If you have a standard non-programmable thermostat, upgrading is a worthwhile investment.
Is your thermostat in a good location? Thermostats near heat sources (sunny windows, lamps, kitchen appliances) or drafts (near exterior doors or vents) read temperatures inaccurately and cause the system to run when it shouldn’t. The thermostat should be on an interior wall away from heat sources, drafts, and direct sunlight.
Part 5: Appliance and Lighting Assessment
The Phantom Load Audit
Phantom load — electricity consumed by devices in standby mode — accounts for 10% of the average household’s electric bill.
Walk through your home and make a list of every device that:
- Has a standby light or display
- Has a clock
- Has a charger plugged in (even with nothing connected)
- Stays in “instant on” mode
Common high phantom load devices:
- Cable boxes and streaming devices (often the worst offenders — some draw 10-20 watts continuously)
- Game consoles
- Microwaves (the clock)
- Coffee makers
- TVs in standby
- Phone and laptop chargers left plugged in
The Kill A Watt test: If you have a plug-in electricity usage meter, test your standby devices individually. Some devices that seem like they’d draw nothing actually consume significant power continuously.
Power strips with switches allow turning off multiple devices simultaneously — one switch instead of unplugging five things. Smart power strips cut power to peripheral devices when the main device (TV, computer) turns off.
Lighting Audit
Walk through every room and note which bulbs are not yet LED. Incandescent bulbs use 75% more energy than equivalent LED bulbs and produce significant waste heat that adds to summer cooling loads.
The replacement plan: You don’t have to replace all bulbs at once. Prioritize the lights used most hours per day — living room, kitchen, primary workspace. Replace bulbs as they burn out with LED equivalents. Within a year or two the transition is complete with no upfront batch expense.
Major Appliance Age and Condition
Older appliances use significantly more energy than current models. Note the approximate age of:
- Refrigerator (significant energy user, runs continuously)
- Washing machine
- Dishwasher
- Dryer
- Water heater
An appliance over 15 years old is likely using 20-40% more energy than a current Energy Star model. This doesn’t mean replacing immediately — the energy saving rarely justifies replacement of a working appliance. But when an older appliance needs replacement, upgrading to an efficient model is financially justified by ongoing energy savings.
Refrigerator efficiency check: The refrigerator is the largest continuously running appliance in most homes. Ensure door seals are intact (the dollar bill test — close the door on a dollar bill; if it slides out easily, the seal is weak), coils are clean, and temperature is set appropriately (35-38°F for fridge, 0°F for freezer).
Part 6: Water Heating Assessment
Water heating accounts for 14-18% of home energy use — a significant share that’s often overlooked in energy audits.
Water heater age and condition: Water heaters typically last 8-12 years. An older unit is less efficient than a newer one and approaching the end of its reliable life. Note the age (usually on the label) and plan accordingly.
Temperature setting: Most water heaters come factory-set to 140°F — higher than necessary and a source of wasted energy maintaining temperature at that level. 120°F is recommended by the Department of Energy as the optimal balance between safety and efficiency. Check and adjust the setting as covered in our lower your water bill guide.
Pipe insulation: Hot water pipes that run through unconditioned spaces (basements, crawl spaces) lose heat to the surrounding air before reaching your faucet. Foam pipe insulation ($0.50-1.00 per foot at hardware stores) maintains water temperature in the pipe and reduces how long you wait for hot water — reducing both water waste and energy waste simultaneously.
Water heater insulation: Older water heaters (pre-2015 approximately) may benefit from a water heater insulation blanket ($20-30) that reduces standby heat loss. Modern water heaters are already well-insulated and don’t typically benefit from additional blankets.
Prioritizing Your Findings
After completing the audit, you’ll have a list of issues. Prioritize them by:
Highest impact, lowest cost:
- Sealing air leaks (caulk, weatherstripping, door sweeps) — $20-50 total, significant energy savings
- Replacing remaining incandescent bulbs with LED — minimal cost, immediate savings
- Fixing phantom load (power strips, unplugging) — zero cost, 10% bill reduction
- Adjusting water heater temperature — zero cost, immediate savings
Moderate cost, significant long-term return:
- Adding attic insulation — $500-3,000 depending on approach, pays back in 3-7 years
- Upgrading to programmable thermostat — $25-50 DIY, pays back in months
- Duct sealing — $50-200 DIY in accessible areas, pays back in 2-4 years
Higher cost, considered at replacement:
- Window replacement — expensive, often 20+ year payback — only worth it at end of window life
- HVAC upgrade — worth considering when current system needs replacement
- Major appliance upgrades — only at end of useful life
The Professional Audit Option
A DIY audit finds most issues. A professional audit adds:
- Blower door test: Pressurizes the home to quantify total air leakage and identify sources more precisely
- Duct blaster test: Measures duct leakage specifically
- Thermal imaging: Cameras that see heat loss through walls and ceilings
- Documentation for utility rebates: Many utility rebates require a professional audit report
Cost: $150-400, sometimes subsidized or free through utility programs.
When worth it: If your utility bills seem disproportionately high and your DIY audit didn’t find obvious causes, a professional audit may identify issues the DIY process missed. Also worth pursuing if your utility offers significant rebates contingent on professional audit documentation.
Tracking Your Results
The value of an energy audit is only realized if you act on the findings and can measure the improvement.
After completing improvements:
- Track your utility usage monthly (not just cost — usage in kWh or therms, since cost can change with rate adjustments)
- Compare to the same period last year
- Calculate the payback period on any investments made
An air sealing project that cost $50 in materials and reduced monthly energy costs by $25 pays back in two months. An attic insulation project that cost $1,500 and reduced annual energy costs by $400 pays back in 3.75 years. Knowing these numbers motivates the next improvement and builds the habit of treating your home as a system to optimize rather than a fixed cost to accept.
Combined with the specific strategies from our save money on your electric bill, cheapest ways to heat your home, and lower your water bill guides, the energy audit is the diagnostic that tells you which of those strategies will have the highest impact in your specific home.
What did you find when you looked for drafts and energy leaks in your home — and what was the most surprising discovery? Drop it in the comments!
