Attic fan cost dataset

Four machines and three trades

⚠️ The last column reads “n/a” on the whole-house fan and that is not a gap in the data — it is a different machine. A whole-house fan takes its air from the house on purpose, through windows you open, so the pressure arithmetic that applies to the three above it does not apply to it at all. Publishing a number there would be answering a question that is not being asked. And on the solar row: no running cost, and the same figure in the last column, because solar removes one of the two federal objections and not the other.

The intake arithmetic, which is the point of this page

One square foot of free intake area feeds about 300 CFM, and a fan is sized at about 0.7 CFM per square foot of attic — so this attic’s fan wants 3.33 square feet. Ordinary soffit vents give under two. ⚠️ The fan does not slow down to match; it takes the difference out of the conditioned rooms below. DOE Building America Solution Center, Attic Ventilation Fans (read 2026-08-25) describes it: “The primary reason that attic fans can increase energy consumption and moisture issues is that they create a negative pressure zone inside the attic.” and “This negative pressure draws conditioned air from the living space into the attic through gaps in the ceiling.” This table is that warning with a number attached, which is the part nobody publishes.

What it costs to run, and what this page refuses to compute

The fourth row is the important one, and it says what it says on purpose. What a fan saves depends on the attic, the ductwork, the climate and how leaky the ceiling is, and a national figure would be an invention — so this dataset does not produce one. What it produces is what the fan costs, from EIA, Electric Power Monthly, table 5.6.B — residential price by state (May 2026, year to date), and what the Department of Energy publishes about the balance: “Studies have shown that they can use more electricity for powering the fan than they save in A/C consumption.” ⚠️ Two consequences that are not financial at all and belong next to any price: “Combustion appliances (other than sealed combustion) may not draft as well or could potentially backdraft.” and “Unhealthy air from garages and crawl spaces can be pulled into the living space. Radon gas can be pulled into basements and crawl spaces.”

Line items

63% of the reference total comes from estimated rather than official figures; the official half is the labour. The reference job is a roof-mounted powered ventilator on a 1,400 square foot attic with ordinary soffit vents, a new circuit and a permit: 1,000 CFM, 7.5 trade hours. Options that are not selected sit at zero quantity, so the table below is all four machines rather than one job.

The reasoning behind each figure

Roof-mounted powered ventilatorestimated, ±50%

• The fan, its housing and a thermostat. Cheap to buy, which is most of why they are still sold.

Gable-mounted powered ventilatorestimated, ±50%

• The same machine in a housing that bolts to a gable wall behind an existing louvre. ⚠️ No roof penetration, which is worth more than the price difference: nothing to flash and nothing to leak later.

Solar-powered attic ventilatorestimated, ±48%

• ⚠️ Two to three times the price of the mains version and nothing to run afterwards, with the panel integrated or separate. It removes the running cost objection entirely; it does not remove the pressure one, and the federal guidance is about both.

Whole-house fan, ceiling mountedestimated, ±58%

• A different machine: a large slow fan in the ceiling with insulated motorised shutters, which is what stops it being a hole in your insulation for the other nine months of the year.
• ⚠️ The band is wide because the cheap ones are a bare fan behind a plastic grille and the dear ones are ducted, quiet and properly sealed when shut. On a machine that lives in the ceiling of a bedroom, quiet is not a luxury.

Capacity, priced by the air it movesestimated, ±46%

• ⚠️ Separated from the body of the unit on purpose, and it is a correction: the first version priced every fan flat by type, so a fan for a 3,000 square foot attic cost the same as one for 1,400. Changing the attic size moved nothing at all, which was visible the moment the page was opened in a browser and invisible to every check.
• A bigger fan is a bigger motor and a bigger housing. It is also the line that makes the intake arithmetic bite: the more air the fan is sized to move, the more of it your soffits cannot supply.

Cutting in and flashing the roof penetration

• Three and a half hours: setting out between rafters, cutting the deck, lifting and re-laying the covering around the flange, and sealing it.
• ⚠️ This is the answer to whether a roofer does this job: for anything that goes through the roof, yes, and it is not a job to give to whoever is cheapest. A fan flange badly flashed is a leak that shows up in a bedroom ceiling two winters later.

Framing and fitting the unit

• Two and a half hours for a gable unit behind an existing louvre. ⚠️ Eight for a whole-house fan, because that one means cutting a joist and heading it off in a ceiling that is holding up a ceiling — it is structural carpentry in a confined space, and it is why the two products are nothing like the same job.

Dedicated circuit, switch and control wiringestimated, ±56%

• Cable from the panel into the attic, a breaker, a disconnect and the control wiring. ⚠️ Google asks whether an electrician is needed on this search, and this line is the answer: for anything with a plug on it, yes — unless there is already a circuit in the attic, which in most houses there is not.

Running and terminating the circuit

• Four hours from the panel to the attic and back to a switch, working in a roof space in whatever the weather is doing outside. ⚠️ Zero on a solar unit, which is the whole point of a solar unit — there is nothing to connect.

Humidistat as well as a thermostatestimated, ±56%

• A control that also runs the fan on humidity rather than only on temperature. It is sold as protection against winter attic moisture — and it is worth reading what the federal guidance says about where that moisture comes from before buying one, because a fan pulling house air into a cold attic is a cause of it rather than a cure.

Sealing the ceiling: foam, caulk and gasketsestimated, ±46%

• ⚠️ This is the line the federal guidance points at instead of the fan, and it is the one that makes a fan safe to own if you are going to own one. Every penetration through the ceiling — light fittings, pipes, the hatch, the top plates of every wall — sealed so that the attic cannot draw on the rooms below.
• Priced per square foot of ceiling because that is how the work scales, and it is cheap next to what it stops.

Finding and sealing the leaks

• One hour per 130 square feet of ceiling plus three, crawling an attic on hands and knees over joists, which is most of what this costs.

Permit and inspectionestimated, ±58%

• A new circuit or a new opening in a ceiling structure is usually permitted work. Set locally, and often waived for a like-for-like replacement of a unit that is already there.

Not included in this dataset

What it saves on air conditioning

⚠️ Deliberately not given a number, and this is the most important exclusion on the page. The calculator computes exactly what the fan costs to run, because that is arithmetic — watts, hours, and your state’s published electricity price. It does not compute what it saves, because that depends on the attic, the insulation, the ductwork, the climate and how leaky the ceiling is, and a national figure would be an invention. What can be said is what the Department of Energy publishes: studies have found these fans can use more electricity than they save. That is a finding, not a calculation, and it is quoted rather than modelled.

Adding intake vents

Cutting in more soffit venting is roofing work and is not priced here. ⚠️ It matters because a powered fan with too little intake takes the difference out of your house — the calculator publishes how much — and the fix is either more intake or a smaller fan. Continuous vented soffit usually comes with a re-roof, which is priced on our roof replacement page.

Insulation

Air sealing is priced here because it is the thing the federal guidance recommends in place of the fan. Insulation itself is a different job and is on our attic insulation page — and the order matters: seal first, then insulate, because insulation laid over unsealed penetrations hides them for good.

A combustion safety check

⚠️ Not a cost on this page and it is the one worth naming anyway. If the house has an atmospherically vented water heater, boiler or furnace, a fan that depressurises the attic and pulls on the ceiling can interfere with how those appliances draft. That is a check for whoever services them, and it is worth asking for before adding a fan rather than after.

Replacing one that already exists

Swapping a dead unit for an identical one is a fraction of these figures: the opening, the flashing and the circuit are all already there. It is also the moment to ask whether to replace it at all, which is what the rest of this page is about.