Freeze Dry Math

Guide

How to Measure Your Freeze Dryer's Real Electricity Use

October 22, 2026

Rows of digital electricity meters on a building wall in Indianapolis
Photo: Jon Moore on Unsplash

Electricity is usually the largest running cost of a home freeze dryer, and it is also the number people guess at most. Harvest Right publishes average and peak current for each model, and our cost per batch calculator turns those into an estimate. An estimate is a fine place to start. One measured batch is better, and a few measured batches are better still.

What the published figures say

Harvest Right’s own article on running costs gives these figures:

Model What Harvest Right gives What our calculator uses
Small and Medium 13–15 A at peak, averaging about 9–11 A (990–1,210 W) 1.0 kW Small, 1.1 kW Medium
Large about 13 A (1,500 W) at peak 1.3 kW, since only a peak is given
X-Large about 18 A at peak, averaging about 15 A (1,700 W) 1.7 kW
Countertop 360 not published yet 0.9 kW placeholder

Notice that for the Large only a peak figure is published, and for the Countertop 360 nothing is. Those are exactly the machines where your own measurement is worth the most.

Why your number will differ

A freeze dryer does not draw a steady load. The refrigeration system works hardest early in the batch, when it freezes the food and then catches water vapor on the chamber walls. The vacuum pump runs through most of the cycle, and the shelf heaters switch on and off. How much energy all that takes depends on things the published figures cannot know:

  • How long the batch runs. Watery fruit and thick pieces take longer. Extra dry time adds hours at the end.
  • How full the trays are. More water to remove means more work.
  • Whether the food went in frozen. Pre-frozen food can shorten the freezing stage.
  • The room. A warm garage in July makes the refrigeration work harder than a cool basement.

So treat any single figure, including one you measure, as one data point.

What you need

A plug-in energy meter sits between the outlet and the machine’s plug and counts kilowatt-hours. Before you buy one, check two things:

  1. The current rating on the label. Many plug-in meters are made for standard 15-amp outlets. The Small and Medium can peak at 13–15 A and the Large at about 13 A, which is close to that limit, so choose a meter rated for at least the machine’s peak. The X-Large uses a 20-amp circuit and peaks around 18 A; measure it at the panel with a circuit-level energy monitor or a smart breaker, or ask an electrician.
  2. That it counts kWh, not just watts. A watts reading is a snapshot. You want the running total for the whole batch.

Plug the meter straight into the wall outlet the machine normally uses. Do not add an extension cord or power strip to make room for it.

How to measure one batch

  1. Reset the meter’s kWh total just before you start the batch.
  2. Write down the date, the food, the fresh weight you loaded and roughly how warm the room is.
  3. Let the batch run as usual, including any extra dry time.
  4. When you end the batch, read the kWh total before you unplug anything, and note the total hours from the machine’s screen.
  5. Divide kWh by hours to get the average draw in kW.

A worked example

Here is how the numbers come together for an illustrative Medium batch of 28 hours, at the US average residential price of 18.31 cents per kWh that the US Energy Information Administration reported for July 2026. The meter reading is an example, not a measurement of ours.

Estimate Example meter reading
Average draw 1.1 kW 0.88 kW
Energy for 28 hours 30.8 kWh 24.6 kWh
Electricity cost $5.64 $4.50

In this example the meter came in about 20% under the estimate. Your batch could just as easily come in over it, especially in a warm room or with a long cycle. That is the point of measuring.

In the cost per batch calculator, choose “I measured it” and enter the meter reading. It uses your kWh instead of the estimate and shows how far apart the two are.

Keep a short log

One batch tells you little. Four or five of different foods show your pattern. A simple log is enough:

Date Food Fresh weight Hours kWh kW (kWh ÷ hours) Room

Once you have a few rows, use the average kW in the calculator for future estimates, and use real kWh per batch in the payback calculator if you are checking whether the machine pays for itself.

Reading your bill against it

Your utility bill shows total kWh for the month and your rate. Some plans charge more at certain hours, so if you are on a time-of-use rate, the cost of a batch depends on when it runs as well as how long. Check the rate schedule on your bill or your utility’s website before you assume a single price per kWh.

Sources

Run your own numbers

Freeze Dryer Cost per BatchElectricity, bags, absorbers and oil per batch, per pound fresh and per ounce dried.Freeze Dryer Payback CalculatorHow many batches until the machine pays for itself versus buying freeze-dried food.Batch Time EstimatorA realistic hour range for a food, adjusted for thickness, load and room temperature.