Our Top Picks
COMFORT ZONE Reversible Twin Window Fan with 3-Speeds9 inch (3-Speed)4.88 x 22.5 x 10.88 Inches4.6 PoundsCheck on Amazon
COMFORT ZONE Reversible Twin Window Fan with 2-Speeds9 inch (2-Speed)5.5 x 11.88 x 22.5 inches5.49 PoundsCheck on Amazon
The Lasko Weather-Shield 3720 is the strongest pick when rain might reach the window because it is the one box fan in several roundups described as having a weather-resistant motor; the Air King 9155 suits shoppers who want a metal, high-circulation fan for general room use, and the Holmes twin window fan suits narrow sashes on a modest budget. Because a window fan sits in an open sash, the most important checks are window fit, rain exposure and safe plugging, not just raw airflow.
At a Glance: Box and Window Fans Compared
| Model | Type | Best for | Stated or reported traits | Limits |
|---|---|---|---|---|
| Lasko Weather-Shield 3720 | 20 inch box fan | Window use where rain is possible | Baby Bargains picked it for the shielded motor; a second reviewer calls it the only fan in its roundup with a weather-resistant motor; 2-year limited warranty | Still keep the cord and plug dry and follow the manual |
| Air King 9155 | 20 inch metal box fan | Whole-room circulation | Won for circulation in Reviewed’s testing, according to the outlet | Not rain-rated |
| Air King 9723 | Box fan with adjustable feet | Budget buyers, uneven sills | Adjustable stabilizer feet; an outlet notes it isn’t rain-safe | Keep away from rain |
| Air King 9166F | 20 inch whole-house style window fan | Power users | TechGearLab rated it highest for power | Costs more than the others |
| Genesis 20 inch | Box fan | Pulling in outside air on low and medium | Praised for a copper motor by a reviewer | Genesis twin window fans scored lower with TechGearLab |
| Holmes dual 8 inch HAWF2041-N | Twin window fan | Narrow windows, value | Reviewed calls it an excellent value | Less airflow than a 20 inch box fan |
| Vornado Transom AE | Window fan (not a box fan) | Premium quiet, compact use | Reviewed’s top overall window fan | Higher tier |
| Lasko W09560 twin | Smart twin window fan | Smart-home control | Today’s Homeowner’s pick for smart features | Needs a compatible setup |
Some of these roundups are older than their 2026 labels suggest, and several are affiliate-driven. Confirm that each model is still sold and read the current manual before buying.
COMFORT ZONE Reversible Twin Window Fan with 3-Speeds & Expandable Width | Draw Cool Air In or Manually Reverse to Pull Warm Stale Air Out, Removeable Bug Screen, ETL Certified for Home and Kitchen
Chosen because it specifies Removeable Bug Screen and ETL Certified for Home and Kitchen.
View on AmazonCOMFORT ZONE Reversible Twin Window Fan with 2-Speeds & Expandable Width | Draw Cool Air In or Manually Reverse to Pull Warm Stale Air Out, With Bug Screen & Fabric Cover, ETL Certified for Home
Chosen because it specifies With Bug Screen & Fabric Cover and ETL Certified for Home.
View on Amazon
10 inch Box Fan, Small Window Fan with 3 Speeds, 8HRS Timer Function Quiet Square Fan for Bedroom Office Kitchen Home Apartment RV Camping, Powered by DC Adapter Work with Universal USB Type-C Cord
Chosen because it specifies Small Window Fan with 3 Speeds and Powered by DC Adapter Work with Universal USB Type-C Cord.
View on Amazon
COMFORT ZONE 20-Inch Portable Box Fan with 3-Speed Control - Black | Portable 3-speed floor and window box fan. Features high-performance blades and a convenient carry handle for easy transport.
Chosen because it specifies Black.
View on AmazonBox Fan vs Purpose-Built Window Fan
A plain box fan is a square fan with a frame, and many people set one in a window with the sash lowered onto the frame. It is cheap and strong, but it isn’t designed to seal the opening. A purpose-built window fan has side panels that expand to fit the sash and often includes two fans, with reversible airflow to pull cooler air in or push hot air out. Reviewers who prefer a box fan for windows usually do so for the larger blades and stronger airflow, accepting looser fit.
Fit and Safety Notes
- Window width: A 20 inch box fan is about that wide plus the frame. Measure your sash opening and the frame depth; many double-hung windows need the sash to rest on the fan’s top edge.
- Gaps: Fill side gaps with foam, cardboard or an insulated panel so insects and rain do not enter, and keep the fan stable so it can’t fall.
- Rain exposure: Only a fan with a shielded or weather-resistant motor, such as the Lasko Weather-Shield, is described as suitable where rain could hit it. Others, like the Air King 9723, are not. Remove or cover them when rain is forecast.
- Cord and outlet: Plug directly into a grounded outlet where possible. Use only extension cords that the fan’s manual permits, and never run cords through a closing window or under rugs. A damaged cord or plug means stop using the fan.
- Children and pets: Choose fans with grills that meet the maker’s stated safety standards, and place the fan out of reach.
- Safety marks: Look for listed electrical certification marks and a stated rating on the product label.
- Intake or exhaust: Cooling works best at night when the outside air is cooler. At the hottest hours, an exhaust setup pulling hot air out and drawing air in through a second window helps.
Features to Compare
| Feature | Why it matters |
|---|---|
| Motor type | Copper or shielded motors are marketed for durability or weather resistance |
| Speed settings | Three settings are common; low is quieter for sleeping |
| Frame material | Metal frames, as on the Air King 9155, are described as sturdier than plastic |
| Feet or stand | Adjustable feet can steady a fan on an uneven sill |
| Reversible airflow | Twin window fans often flip direction |
| Warranty | Lasko lists two years on the 3720 |
| Noise | Larger blades at lower speed tend to be quieter |
Pick X If… Decision Table
| If you… | Pick | Why |
|---|---|---|
| Worry about rain | Lasko Weather-Shield 3720 | Shielded motor |
| Want maximum circulation | Air King 9155 | Won for circulation in one review |
| Have an uneven sill | Air King 9723 | Adjustable feet |
| Have a narrow window | Holmes twin or Lasko W09560 twin | Expandable side panels |
| Want a quieter premium option | Vornado Transom AE | Top overall in one roundup |
| Want to pull outside air on a budget | Genesis 20 inch | Reviewer praised it on low and medium |
Alternatives
- Tower or pedestal fan: Better for in-room cooling when you don’t want to block the window.
- Portable air conditioner or window AC: Needed in hot, humid conditions where moving air isn’t enough.
- Whole-house fan: Installed in the attic; consult a licensed contractor and electrician.
Placement and Airflow Tips
- Use the cool side: At night, place the fan on the shadier side of the house and draw outside air in, with another window open on the opposite side to let warm air exit.
- Daytime: If the outdoor air is warmer than indoors, keep windows closed or use the fan to exhaust air from the hottest room only.
- Stabilize the fan: Use the fan’s feet or a level sill. Do not let the fan lean against glass.
- Dust and pollen: A box fan draws in whatever is outside. Clean the grill and blades regularly according to the manual, with the fan unplugged.
- Air quality days: If outdoor air is smoky or has a high pollen count, close the window and use a fan that only circulates indoor air.
Noise and Sleeping
Box fans produce a broad hum that some people find soothing, while others find it distracting. A larger fan at low speed is usually quieter than a smaller fan at high speed, and rubber feet or foam strips between the frame and sill reduce vibration. Twin window fans can feel quieter at a given airflow because the blades are smaller but spread across two fans, though models differ. Reviewers who rank quiet window fans often put the Vornado Transom AE near the top, which also sits in a higher tier.
Winter and Storage
Remove the fan when not in use and seal the window. Store the fan in a dry place, wrapped to keep dust off the grill. Check the cord for cracks or fraying before the next season and replace the fan if the cord or plug is damaged.
Budget Tiers
At the budget tier, a basic 20 inch box fan with adjustable feet, such as the Air King 9723, covers general circulation, though it is not rain-rated. The mid-range tier brings shielded or metal-built fans like the Lasko Weather-Shield 3720 and Air King 9155, which reviewers prefer for durability or weather resistance. The premium tier is dominated by purpose-built window fans such as the Vornado Transom AE or whole-house style units like the Air King 9166F, which cost more but move air with less fuss.
Final Selection Tips
Measure the window opening first, then choose between a single box fan and a twin window fan. If rain exposure is likely, choose a fan whose maker states the motor is shielded, and still unplug it during storms. Prefer a fan with a stable base, a sturdy grill and an undamaged cord, and read the manual for any limit on window use or extension cords.
Frequently Asked Questions
Can I use a regular box fan in a window?
Many people do, resting the lowered sash on the frame and sealing gaps. It works best when the fan is stable and kept out of rain. Check that the manual doesn’t forbid it.
Which box fan is safe in the rain?
Reviewers single out the Lasko Weather-Shield 3720 for its weather-resistant motor. Even then, keep plugs and cords dry and follow the manufacturer’s guidance about exposure.
Should the fan blow in or out?
Blowing out is useful on hot afternoons to exhaust warm indoor air while another window is open. Blowing in works at night when the outdoor air is cooler. A two-fan setup, one in and one out, moves air through the home.
How do I keep bugs out when a fan is in the window?
Close the gaps around the fan with foam or a panel, or use a fan with a built-in expandable side panel. A window screen on the outside also helps.
Can I leave a window fan running overnight?
Many people do, but use a fan in good condition with an undamaged cord, plug directly into a grounded outlet, and follow the manual. If the fan smells hot or makes unusual noise, unplug it.
Are twin window fans better than box fans?
They fit windows more neatly and can reverse airflow, but a single 20 inch box fan usually moves more air on high. The right choice depends on your window size and how often you need to seal gaps.
