How Numberwright Freeze-Dry calculates

Yield and water removed

Freeze-drying sublimates ice directly into water vapor under vacuum. Solids are conserved throughout the process:

• Solids = fresh weight × (1 − water %)
• Dry weight = solids ÷ (1 − moisture left %)
• Water removed = fresh weight − dry weight
• Yield % = (dry weight ÷ fresh weight) × 100
• Measured residual % = max(0, (1 − solids ÷ dry weight) × 100)

Running cost

The batch running cost accounts for utility power and consumable packaging:

• Energy (kWh) = measured kWh, or average watts × hours ÷ 1,000
• Electricity cost = energy (kWh) × electricity price per kWh
• Packaging cost = (bags × price per bag) + (absorbers × price per absorber)
• Total cost per batch = electricity + packaging + other costs
• Cost per fresh lb = total cost ÷ fresh weight in lb
• Cost per dry oz = total cost ÷ dry weight in oz

Oxygen absorbers

Air is approximately 21 % oxygen. Absorbers must scavenge the oxygen volume remaining in the sealed container:

• Conservative mode: residual air = container volume (safe for porous freeze-dried food)
• Dense mode: residual air = max(0, container volume − product weight in grams) (Sorbent Systems method)
• Oxygen volume (cc) = residual air × 0.21
• Required capacity (cc) = oxygen volume × (1 + safety margin %)
• Packet selection: combinations of up to 4 packets evaluated for fewest packets, smallest total capacity, and preference for larger single packets

Rehydration

To return dry food to its original fresh hydration level, the water that was removed is added back:

• Original fresh weight = dry weight × (1 − moisture left %) ÷ (1 − water %)
• Water to add = original fresh weight − dry weight (1 g water = 1 mL)

Payback

Compares the cost of owning and running the machine against buying equivalent commercial freeze-dried food:

• Saving per batch = store price of equivalent food − cost per batch
• Batches to break even = (machine price + accessories) ÷ saving per batch
• Months to break even = batches to break even ÷ batches per month

Where the water contents come from

Water contents are from the USDA National Nutrient Database for Standard Reference, Release 28 (2015), a US government dataset. Real food varies with variety and ripeness; you can edit the value.

What we don't do

We don't predict batch times and we don't promise shelf life.