Start with the bill, because the house lies and the meter does not
Before touching anything, pull twelve months of electric statements and twelve months of whatever fuel heats the place. One month tells you nothing; a year tells you the shape of the house. Write down the kWh for each month, not the dollars, because rates move and dollars hide the pattern.
The shape is the diagnosis. A summer hump and a winter hump means both systems are working hard. A winter hump several times the size of the summer one, in a house with electric heat, is ordinary. A summer hump in a house with no air conditioning is a dehumidifier, a pool pump, or a chest freezer in a hot garage running its compressor continuously.
The other number worth extracting is the flat bottom of the year — the lowest month, usually a mild one in spring or fall when neither system runs much. That figure is roughly what the house costs to exist: refrigeration, water heating, lighting, electronics, and whatever is on all the time. Everything above that line in January and July is climate.
One piece of arithmetic, used everywhere on this site
Every energy question in a house reduces to the same three-step calculation, and it is worth doing by hand once so the number stops being abstract.
Watts, multiplied by hours of running, divided by 1,000, gives kilowatt-hours. Multiply kilowatt-hours by the rate on your own bill and you have dollars.
Take a 1,500-watt portable heater in a room somebody works in eight hours a day. 1,500 x 8 = 12,000 watt-hours, divided by 1,000 is 12 kWh a day. If the rate on your statement works out to 16 cents a kWh, that is $1.92 a day and about $58 in a thirty-day month, for one room, from one appliance you can pick up with one hand. Run the same arithmetic on a 60-watt aquarium pump that never turns off: 60 x 24 = 1,440 Wh, or 1.44 kWh a day, 43 kWh a month, near $7. Small and constant beats large and occasional more often than people expect, and the only way to tell which is which is to do the multiplication.
Get the rate from your own statement, and get it the honest way: divide the total bill by the kWh used. That folds in the delivery charges, fixed customer charge and taxes, which are frequently a third or more of what you actually pay and are missing from the headline energy rate. US rates vary enormously by utility and by rate plan — a figure quoted on a web page, this one included, is worthless next to the one on your own paper. The electricity bill calculator will separate the pieces if your statement is hard to read.
What a professional audit actually does
| Test | What it measures | What it finds that you cannot |
|---|---|---|
| Blower door | A calibrated fan in an exterior doorway depressurizes the house, and the airflow needed to hold a set pressure difference is the leakage rate | A single number for how leaky the house is, comparable to other houses and to a target. It also turns every leak into a draft you can feel while the fan runs, which is how the auditor finds them. |
| Infrared scan | Surface temperature across walls, ceilings and floors, usually with the blower door running | Missing insulation inside a closed wall, insulation that has slumped in a cavity, thermal bridges, and wet material. None of this is visible any other way without opening drywall. |
| Duct pressurization | Leakage of the duct system itself, tested separately from the house | How much of the air you paid to heat or cool is being delivered to an attic or crawl space instead of a room |
| Combustion safety and draft testing | Whether furnaces, boilers and water heaters vent properly, and whether they still do it when the exhaust fans and dryer are running | Backdrafting. This is a safety finding, not an efficiency one, and it is the reason air sealing work should be paired with a combustion check. |
| Carbon monoxide and ambient testing | CO in living space and in the flue | A cracked heat exchanger or a spilling water heater, before anyone gets sick |
Many utilities run subsidized or free assessments, and income-qualified households can often get the work itself covered through a weatherization program. The details are state and utility specific and change; ask your utility what it currently offers rather than trusting any list. What is worth insisting on is that you get the numbers — the leakage figure, the duct result, the scan images — not just a sales sheet with a recommended product on it.
The homeowner version, in an afternoon
You will not get a number, but you will find most of the same leaks. Pick a windy, cold day, because the pressure difference across the shell does for free what the blower door does deliberately.
| Check | How | Typical finding |
|---|---|---|
| Back of the hand, slowly, around every opening | Wet the back of your hand and move it along door frames, window sashes, the sill plate in the basement, and where pipes and wires come through walls | Skin is a better draft detector than an incense stick and does not set anything on fire. Mark every hit with painter tape. |
| Outlet and switch plates on exterior walls | Take the cover off with the power off at the breaker and feel behind it | Air moving through the box means the wall cavity is connected to outside. Foam gaskets behind the plates take a minute each. |
| Attic hatch and the attic floor | Flashlight from the hatch, if the attic is safe to look into | Dark, dirty patches in light-colored insulation are air filtering through it. Those are the leaks. Also look for insulation depth, gaps at the edges, and bath fans discharging into the attic instead of outside. |
| Rim joist, in the basement | Hand check the band of framing at the top of the foundation wall | Usually the worst uninsulated area in the house and the easiest to fix standing up |
| Ducts you can reach | Feel every joint while the system runs | Air blowing out of a seam in a crawl space is money leaving. Mastic, not cloth duct tape. |
| Dryer, bath and kitchen exhaust hoods, from outside | Look at the exterior while each runs | A damper stuck open leaks year round; a damper stuck shut means the fan is doing nothing |
The baseline test — what the house draws when nobody is home
This one takes an evening and tells you more than any inspection. Turn off, unplug or account for everything you can, then read the electric meter, wait an hour without using anything, and read it again. The difference is your baseline: the load that runs whether or not anyone is awake.
A modern, ordinary house with a refrigerator, a couple of network devices and some clocks might sit somewhere in the low hundreds of watts. If yours reads far above that, something is running that you have not accounted for, and the usual suspects are a second refrigerator or freezer in a garage, a well pump cycling because of a leak, a sump pump running on a stuck float, a dehumidifier, an aquarium, electric resistance heat tape, or a hot tub. That single hour of measurement finds line items that no amount of unplugging phone chargers ever will. If your utility gives you interval data through an online account, you have the same information in more detail and without the wait.
Ranking what you found
The order below is not a ranking of how big each loss is. It is a ranking of dollars spent against comfort and savings returned, and it holds in most houses because the cheap items are cheap and the expensive items are expensive.
| Rank | Work | Why here |
|---|---|---|
| 1 | Air sealing the attic plane and the rim joist | Small material cost, immediate comfort change, and it must happen before insulation goes down or you can no longer find the leaks. Covered in detail in insulation and condensation. |
| 2 | Sealing ducts that run outside the conditioned space | The loss is invisible and frequently large, and mastic costs almost nothing |
| 3 | Attic insulation to the depth your climate zone calls for | Cheap per unit of R, and the attic is the most accessible cavity in the house. The insulation calculator turns an R-value into bags or batts. |
| 4 | Water heating: temperature setting, tank blanket, pipe insulation on the first few feet | Second largest end use in a typical home and the interventions are inexpensive |
| 5 | Behavior and scheduling — thermostat setbacks, an old second refrigerator retired | Free or near free, and a retired garage freezer is a real line item |
| 6 | Replacing heating or cooling equipment | Last, deliberately. Equipment sized for a leaky house is bigger, costs more, and then loses more. Seal first and the replacement can be smaller. |
| 7 | Windows | The most expensive comfort per dollar of anything on this list. Weatherstripping, storm panels and window film capture much of the benefit for a fraction of the cost. |
What an audit will not tell you
It will not tell you what your bill will be next year, because that depends on weather, on how you live in the house, and on a rate structure that can change under you. Treat any promised savings figure as an estimate built on assumptions someone chose, and ask what they were. It will also not settle incentive questions: federal, state and utility programs stack, change on their own schedules, and have eligibility rules no page should quote. Check what is current with your utility and your state energy office yourself before signing anything.
Where an audit earns its money is in ranking. Almost everyone knows their house is leaky somewhere. Very few know which of the candidates is worth two hundred dollars of foam and which is worth nothing, and guessing is how the window salesman ends up with the whole budget.
Do the meter baseline test tonight. It takes an hour of not using anything, needs no tools, and in a surprising number of houses it turns up a running load that outweighs everything else here combined. From there, heating cost and cooling cost take the two halves of the year separately.
Questions people ask
Is a professional energy audit worth paying for?
It is worth it when you are about to spend real money and do not know where. The value is not in being told the house is leaky — you already suspect that — but in ranking the leaks, which a blower door and an infrared camera do and no amount of walking around does. If the plan is a few hundred dollars of caulk and foam, do the hand check on a windy day and skip the audit. If the plan is insulation, duct work or replacement equipment, get measured first. Ask your utility what assessments it currently subsidizes, and insist the report hands you the actual numbers rather than a product recommendation.
How do I work out what a kilowatt-hour costs me?
Divide the total amount of your electric bill by the kilowatt-hours it covers. That gives an all-in rate including delivery charges, the fixed monthly customer charge and taxes, which together are often a third or more of the total and are absent from the headline energy price. Use that all-in figure in every calculation, because it is what an extra kWh actually costs you. Rates differ enormously between utilities, between rate plans, and in some places by time of day, so a number quoted anywhere other than your own statement is not your number.
What is a baseline load and how do I measure it?
It is what the house draws continuously with nobody actively using anything — the refrigerator, network equipment, clocks, pumps, anything that never switches off. Measure it by shutting down everything you reasonably can, reading the electric meter, waiting an hour without using water or appliances, and reading again. The difference in kWh is your hourly baseline. A number far higher than you expected usually points at a specific object: a second refrigerator or freezer, a well pump cycling because of a leak, a dehumidifier, a stuck sump float, heat tape, or a hot tub. Utility interval data, if your account offers it, shows the same thing without the wait.
Does a thermal camera attachment for a phone actually work?
For the coarse findings, reasonably well. Missing insulation in a wall cavity, a cold band at an uninsulated rim joist and air pouring past a window frame all show up clearly on inexpensive sensors, provided there is a decent temperature difference between inside and out — scan on a cold morning, not a mild afternoon. What the cheap ones will not do is what an auditor does, which is run the scan with a blower door depressurizing the house, so that every leak is actively pulling cold air and lights up. They also invite misreading: a cold spot can be missing insulation, a thermal bridge, or a wet wall, and telling those apart takes more than the picture.
Where should I spend first if the budget is small?
Air sealing, in the attic and at the rim joist, ahead of anything else. It is cheap in materials, changes how the house feels within a day, and has to be done before insulation goes on top or the leaks become unreachable. After that, seal any duct running through an attic or crawl space with mastic. Both of those are afternoons and tens of dollars. Insulation, water heating measures and thermostat habits come next; equipment replacement and windows come last, not because they do nothing, but because they cost the most per unit of comfort and because a house that has been sealed first needs smaller, cheaper equipment.