Treva 10" Fin Fan review: up to 40 hours of air on six D cells

This is a research-based review, based on manufacturer specs and published data. We do not test products. Figures come from O2COOL's product page for the Treva 10" Fin Fan with AC Adapter and USB Charging Port (FD10002AU), checked November 1, 2026, and from the CDC and Ready.gov sources cited below.

The Treva 10-inch Fin Fan takes three power sources: six D-cell batteries, an included AC adapter, or USB. O2COOL rates it at up to 40 hours of battery life, has 10-inch blades and two speeds, and adds a USB port that can charge a phone, tablet or music player. It measures 12.00 × 3.80 × 12.90 inches and has a built-in handle.

For a power outage, D cells are its advantage. They are sold in grocery stores, pharmacies and hardware stores, store for years, and need no charger. If you do not already own cordless tools, this avoids buying into a battery platform just to stay cool at night.

Who should buy it

• Households without Milwaukee, DEWALT or RYOBI tool batteries.
• People who want a fan that sits in a closet for years and works on store-bought batteries when needed.
• Families who want one fan per bedroom without buying several tool batteries.
• Owners of rechargeable D cells, which work in place of alkaline cells and refill from a power station or solar charger.

Who should skip it

• Anyone who needs to cool a large room or a garage. A tool-battery jobsite fan such as the Milwaukee M18 Jobsite Fan is rated far higher.
• People who want oscillation or fine speed control. The Treva has two speeds and no oscillation listed.
• Buyers who already own a cordless tool platform. A tool-only fan uses batteries you already charge.

Strengths

• Long rated runtime. Up to 40 hours of battery life, per O2COOL.
• Common batteries. Six D cells, which are widely sold and store well.
• Three power sources. D cells, the included AC adapter, or USB.
• USB charging port. Top up a phone from the fan's batteries in a pinch.
• Portable. Built-in handle and a slim 3.8-inch depth for a nightstand.

Drawbacks

• Two speeds only, and no oscillation listed.
• No speed named for the 40-hour figure. O2COOL does not say whether it applies to low or high.
• Lighter airflow than tool-battery fans; O2COOL lists no CFM rating.
• Phone charging shortens fan runtime. Every bit of energy sent to a phone comes out of the same six D cells.
• Batteries not included. Stock six D cells per fan, plus spares.

How it compares

The Treva against the other battery fans we review. Figures are from each maker's page.

Using it in a long outage

How many D cells to stock

Treat O2COOL's 40 hours as a best case, likely on low and with fresh alkaline cells. As a conservative planning figure, assume about 20 hours of real use per set of six (our assumption, not O2COOL's). At 8 hours a night, that is two to three nights per set. For a one-week summer outage, stock three sets, or 18 D cells, per fan. Rechargeable D cells cut that cost over time and can be refilled from a power station, but check their capacity: some low-cost rechargeable D cells hold far less than alkaline.

Using the USB port

The USB charging port is handy, but it draws on the same cells as the fan. Keep it for an emergency top-up. For routine phone charging, a power bank or a power station is a better use of energy; our phone charging guide covers the options.

Making the fan count

1. 01Keep blinds closed on sun-facing windows during the day so the house heats up less.
2. 02At night, open windows on the cooler side if outside air is cooler and safe to let in, and set the fan to pull it across the bed.
3. 03Run on low for sleep; use high only for short periods.
4. 04Drink water regularly; CDC advises not waiting until you are thirsty in hot weather.
5. 05Check on older neighbors and anyone living alone, as CDC recommends.
6. 06Take alkaline cells out of the fan for long-term storage so they cannot leak inside it.

Ready.gov's power outage guidance covers the rest of the house. For the full cooling plan, see how to stay cool without power, and for battery choices, best rechargeable batteries for a power outage.