Why Running Fans 24/7 Costs You Tonnage and Power
Leaving aeration fans on around the clock feels safe, but it dries saleable grain, can re-wet it on humid nights, and runs up a power bill. Here's the maths.
SiloSense IQ ·
“Just leave the fans on” is common advice, and it comes from a good place: aeration protects grain, so more aeration must protect it more. In practice, fans running around the clock cost you three ways — power, tonnage and, on the wrong nights, grain quality.
Cost 1: power
A fan running 24 hours a day runs 720 hours a month. Take an illustrative 4 kW fan and 30c per kWh:
- 4 kW × 720 h = 2,880 kWh a month
- At 30c/kWh that’s about $864 a month, per fan
Run the same fan only when the air is right — often a few hours a night — and you might use a quarter of that or less. Across a site with several fans over a storage season, the difference is thousands of dollars. Use your own fan rating and tariff; the proportion is what matters.
Cost 2: tonnage
Through the warmer, drier hours of the day, outside air usually sits below the grain’s equilibrium moisture. Pushing that air through the silo hour after hour slowly dries the grain.
Every percentage point lost comes off the weighbridge weight. On 1,000 tonnes of wheat dried from 12.5% to 11.5%, that’s about 11 tonnes you’ll never be paid for. (See How Much Moisture Loss Is Costing You at the Weighbridge for the full calculation.)
Cost 3: re-wetting
The opposite happens on humid nights and wet weeks. Air near saturation pushed into cooler grain can add moisture — often unevenly, with the top or the leading edge of the airflow taking up the most. Damp layers are where moulds and heating start.
So a fan left on 24/7 can be drying grain in the afternoon and wetting it again at 3am — while you pay for both.
What “enough” aeration looks like
The aim of cooling aeration is to move a cooling front through the grain and keep it cool. That needs a modest number of hours on good air, not maximum hours on any air:
- After harvest, a solid run to get field heat out.
- Then regular, shorter runs on cool air that’s within your humidity limits.
- Rest when the air would do harm.
How SiloSense helps
Aeration Manager replaces “always on” with modes that match the job:
- Forced Run for hot grain straight from the paddock — 10 hours by default, or 1 to 24 hours.
- Automatic runs only when outside temperature and humidity are within your limits.
- Auto Protect gives long-term storage short 30-minute runs with an hour’s rest, aiming for about 3¼ hours a day, and only on suitable air.
The dashboard records run hours for every fan, so you can see what you’re actually spending. Request a demo to compare your current fan hours.