How Much Will It Cost to Dry Corn from 22% to 15%?

Drying corn from 22% to 15% removes seven moisture points. For a gas-fired dryer, a useful first estimate is 0.02 gallon of propane and 0.01 kWh of electricity per wet bushel per point removed. At $2.00 per gallon for propane and $0.15 per kWh for electricity, the estimated energy cost is about $0.291 per incoming wet bushel, or $2,905 for 10,000 wet bushels.

That is an energy estimate, not the complete cost. Labor, repairs, equipment ownership, extra handling, cooling, and possible dry-matter loss must be added. The same 10,000 wet bushels will also become about 9,176 dry-equivalent bushels at 15% moisture, even with no dry matter lost, because about 824 bushel-equivalents of weight are removed as water.

Quick Answer at Common Propane Prices

The following table uses seven points removed, 0.02 gallon of propane per wet bushel per point, 0.01 kWh per wet bushel per point, and electricity at $0.15/kWh.

These are planning numbers. University of Minnesota Extension gives 0.02 gallon per bushel-point as a rough estimate for gas-fired drying. Iowa State Extension reports that actual propane use may range from about 0.010 to 0.025 gallon per bushel-point, depending on the dryer, outdoor temperature, and operating conditions. Actual fuel records from the farm are more useful than a generic coefficient.

The Basic Energy Calculation

Start with the incoming wet bushels, not the bushels that remain after drying.

Moisture points removed

22 − 15 = 7 points

Propane required

Wet bushels × 7 points × propane use per bushel-point

Propane cost

Wet bushels × 7 × propane use × delivered propane price

Electricity cost

Wet bushels × 7 × electricity use per bushel-point × electricity rate

For 10,000 wet bushels, using 0.02 gal/bu-point, 0.01 kWh/bu-point, $2.00 propane, and $0.15 electricity:

If the dryer uses natural gas, diesel, or another fuel, use actual metered energy consumption from a similar run rather than converting the propane estimate blindly. Burner efficiency, heat recovery, drying-air temperature, ambient conditions, and dryer type can make the result materially different.

Why Your Dryer May Be Far Above or Below the Estimate

The 0.02-gallon coefficient is a starting point. It is not a guaranteed consumption rate.

Dryer efficiency

Heat recovery, airflow control, burner condition, grain-column management, and dryer design affect how much purchased energy removes a pound of water. NDSU Extension notes that a more efficient dryer may require about 2,000 Btu per pound of water removed rather than the 2,500 Btu basis used in its general propane formula.

Outdoor temperature

Cold inlet air requires more energy. Iowa State Extension estimates that high-temperature drying cost increases about 14% for each 20°F decrease in average outdoor temperature. This is one reason the same seven-point removal can cost more later in the season.

Incoming moisture variation

A field average of 22% does not mean every load is 22%. If part of the crop arrives at 19% and another part at 25%, a single average can hide uneven dryer loading and increase the chance of overdrying part of the grain.

Record the moisture of representative incoming loads. A portable Grain Moisture Meter can support routine checks and help operators group materially different loads instead of running the entire harvest through one assumed setting.

Target and discharge management

The last point or two can be relatively expensive to remove in the heated dryer. Some systems discharge corn above the final target and use in-bin cooling or dryeration to complete part of the moisture removal. NDSU reports that in-storage cooling may remove about one point, while properly managed dryeration may remove about 2 to 2.5 points and reduce energy use.

Those methods require suitable bins, airflow, timing, and management. Do not subtract an expected cooling loss from the dryer target unless the system is designed and operated for it.

Fines and airflow resistance

Broken kernels, fines, and foreign material restrict airflow. A dryer or bin that must push air through higher resistance can lose capacity and use more electricity. Cleaning and distributing grain properly can therefore affect both cost and throughput.

Convert Wet Bushels to Dry-Equivalent Bushels Correctly

Corn is normally discussed in bushels, but a bushel used in grain settlement is a weight unit. For shelled corn, one standard bushel is 56 pounds. When water leaves during drying, the load weighs less even if every pound of dry matter remains.

Use the moisture-shrink formula:

Moisture shrink % = (initial moisture − final moisture) ÷ (100 − final moisture) × 100

For 22% to 15%:

(22 − 15) ÷ (100 − 15) × 100 = 8.235% moisture shrink

The dry-equivalent bushels are:

10,000 × (1 − 0.08235) = 9,176.5 bushels at 15%

The same result can be calculated by conserving dry matter:

10,000 × (100 − 22) ÷ (100 − 15) = 9,176.5 bushels

The 823.5-bushel difference is water weight expressed in 56-pound bushel units. It is not automatically 823.5 bushels of lost corn.

Moisture shrink is not the same as dry-matter loss

Keep three concepts separate:

If a buyer uses a shrink factor larger than pure water shrink, the difference may represent assumed handling loss or commercial policy. Do not add the full moisture-shrink value to fuel cost as if all of it were an additional operating expense. The correct comparison is net value on the same final-moisture basis.

Add the Costs That the Energy Formula Misses

University of Minnesota Extension cautions that other ownership and operating costs can sometimes be as large as energy cost. A serious estimate should show both cash cost for this drying run and full economic cost.

Variable cash cost

Include costs that rise when more corn is dried:

• Propane, natural gas, or other burner fuel
• Electricity for dryer fans, augers, legs, conveyors, and cooling fans
• Operator labor and monitoring time
• Repairs and maintenance caused by use
• Additional hauling or grain movement
• Cleaning or screening
• Measured handling loss

Equipment and ownership cost

Include the annual cost of having the system available:

• Depreciation
• Interest or opportunity cost on invested capital
• Insurance and property taxes
• Dryer, wet-bin, conveyor, leg, controls, and site costs

Allocate annual ownership cost across realistic annual throughput:

Ownership cost per bushel = annual ownership cost ÷ annual bushels dried

A dryer used for 500,000 bushels spreads its fixed cost differently from one used for 50,000. When deciding whether to run an existing paid-for dryer this week, the variable cash cost may drive the decision. When comparing on-farm drying with commercial drying over several years, full ownership cost matters.

A worksheet for the complete cost

Do not use the same cost in two rows. For example, if a custom drying charge already includes fuel, labor, and equipment, do not add those items again.

Express the Cost on Both Wet- and Dry-Bushel Bases

Dryer formulas are commonly stated per incoming wet bushel, while saleable quantity after drying is lower. Label the basis whenever two options are compared.

In the 10,000-bushel example:

• Energy cost per incoming wet bushel: $2,905 ÷ 10,000 = $0.291
• Energy cost per 15% dry-equivalent bushel: $2,905 ÷ 9,176.5 = $0.317

Neither number is wrong. They answer different questions. The wet-bushel number is convenient for operating-cost estimates. The dry-equivalent number is better for comparing cost with the bushels available to sell after water is removed.

For a per-acre estimate, multiply cost per incoming wet bushel by the actual wet bushels handled per acre. If the crop produces 200 incoming wet bushels per acre at 22%, the example energy cost is about:

200 × $0.2905 = $58.10 per acre

Add labor, repairs, equipment, and handling to reach the full per-acre cost.

Compare On-Farm Drying With the Elevator on the Same Basis

An elevator may use a drying charge per wet bushel per point, a moisture discount, a shrink schedule, or a combination. A lower-looking drying fee can be offset by a larger shrink factor, while an on-farm estimate can look artificially low if it excludes ownership and handling.

Request the buyer's actual terms and calculate:

1. Wet bushels delivered 2. Moisture points assessed 3. Drying charge 4. Shrink factor and final moisture basis 5. Quality or moisture discounts 6. Freight and waiting cost 7. Net dry-equivalent bushels and net revenue

Then compare that result with the on-farm system's full incremental cost and expected dry-equivalent quantity. Iowa State's Corn Drying and Shrink Comparison worksheet is designed for this type of comparison.

Use Actual Dryer Records to Replace the Generic Estimate

The fastest way to improve the calculation is to build a per-run record. For each field, hybrid, or meaningful moisture band, record:

• Representative incoming moisture average and range
• Bushels entering the system
• Final moisture after the normal cooling process
• Gallons of propane or units of other fuel used
• Dryer and auxiliary electricity where available
• Dryer hours and average throughput
• Labor hours
• Outdoor temperature and major weather conditions
• Repairs, interruptions, and grain moved again

Calculate actual propane use:

Actual gal/bu-point = gallons used ÷ (wet bushels × moisture points removed)

If 1,260 gallons dry 10,000 bushels through seven points:

1,260 ÷ (10,000 × 7) = 0.018 gal/bu-point

Use that value for the next similar run. Keep separate records for materially different systems or weather. A single seasonal average may hide a cold-weather penalty or a large change in dryer performance.

The Cost of One Unnecessary Moisture Point

Overdrying from 15% to 14% adds energy cost and removes saleable water weight. Using the example energy rates:

• Extra energy per incoming bushel for one point: 0.02 × $2.00 + 0.01 × $0.15 = $0.0415
• Extra energy for 10,000 incoming bushels: about $415

The remaining corn also weighs less. Corn at 15% dried to 14% loses about:

(15 − 14) ÷ (100 − 14) × 100 = 1.163% of its 15% weight

For 9,176.5 bushels at 15%, that is about 106.7 bushels of additional water weight. At $4.50 per bushel, that weight represents about $480 in gross sale weight, before any quality or contract considerations.

This does not mean every lot should stop at exactly 15.0%. The appropriate target depends on storage duration, moisture variation, cooling, buyer terms, and the consequences of wetter pockets. It does mean that routinely targeting lower moisture without a reason has a measurable cost. For the earlier harvest decision that determines the starting moisture, see What Moisture Should I Harvest Corn At?.

Common Costing Errors

Using a cents-per-point rule without updating fuel price

A historical shortcut can be badly wrong when propane and electricity prices change. Use current delivered prices and the farm's actual consumption when possible.

Treating seven points as 7% of the current moisture

Drying from 22% to 15% means seven percentage points. The fuel coefficient is multiplied by seven. The weight-shrink formula is different and produces 8.235% shrink to a 15% basis.

Calling all shrink a loss of corn

Most weight reduction from 22% to 15% is water. Calculate unavoidable water shrink separately from handling loss and buyer-assessed shrink.

Comparing a wet-bushel cost with dry-bushel revenue

Label the bushel basis. Convert both choices to the same final moisture before comparing net value.

Ignoring dryer capacity

A cheaper cost per bushel may not be the better harvest plan if the system cannot process corn fast enough. Wet-bin limits, dryer throughput, weather, and field losses can outweigh a small fuel saving.

Assuming the field average is the dryer input

Measure representative loads during harvest. A wide moisture range changes cost, capacity, and the risk of overdrying part of the grain.

Should You Wait for 22% Corn to Dry Further in the Field?

Every point removed in the field avoids mechanical-drying energy, but field drying is not free if waiting increases lodging, ear drop, disease, wildlife loss, or harvest delay.

Use the estimated cost per point as one side of the decision. At the example prices, one mechanically removed point costs about $0.0415 per incoming wet bushel in energy. Compare that saving with the yield and quality value at risk, dryer availability, and the expected field drydown over the next few days.

For the full decision process, use Should I Harvest Wet Corn Now or Let It Dry in the Field?. To estimate how many points favorable weather may remove, see How Fast Will Corn Dry Down Over the Next Few Days?.

Bottom Line

At $2.00 propane and $0.15 electricity, a reasonable starting estimate for drying corn from 22% to 15% is about $0.291 per incoming wet bushel in energy, or $2,905 for 10,000 wet bushels. That batch becomes about 9,176 dry-equivalent bushels at 15% before any handling loss.

For a decision-quality number, replace the generic fuel coefficient with actual dryer records, then add labor, repairs, auxiliary electricity, extra handling, and equipment ownership as appropriate. Keep water shrink separate from dry-matter loss, and compare every option on the same final-moisture and bushel basis.

Sources and Further Reading

• University of Minnesota Extension: Energy Costs for Corn Drying and Cooling
• University of Minnesota Extension: Natural-Air Corn Drying
• Iowa State University Extension: Estimating the Cost for Drying Corn
• Iowa State University Extension: Corn Drying and Shrink Comparison
• Iowa State University Extension: Options for Fall Grain Drying and Marketing
• NDSU Extension: Corn Drying and Storage Tips When There Is Early Frost