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Freeze Dryer Power Saving Break-Even Run Calculation Guide
The Importance of Freeze Dryer Power Efficiency for Drying Cost
Highlights:
When deciding on which freeze dryer to purchase, running cost per drying batch must be a key decision factor because it is the primary factor of total cost of ownership.
For example, as calculated below, it only takes 139 runs for the CryoDry CD8 to become cheaper to own than an American XLarge model. At 5 runs per week the break-even period is only 6 months. At 3 runs per week it is 9 months.
Basis of this is a simple cost per run calculation as follows (assuming a 24 run time per cycle):
Cost per Run = Power Consumption (kWh) × Electricity Cost (per kWh) x 24 hours
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Freeze Dryers
| Model Name | Purchase Price ($) | Power Consumption (kWh) | Baseline? |
|---|---|---|---|
Background Information and Detail
With an increasing number of freeze dryer brands on the market, many potential buyers are unsure how to decide what freeze dryer to purchase.
The most important consideration should always be your safety, both personal and property.
As consumers, we expect products offered to us to be safe to use. That is however not always the case, especially when products are purchased from overseas via the internet. Attention should be given to local Electrical Standard Compliance as well as certified Food Safety.
Here are some example resources with detailed information:
Australian and New Zealand Electrical Equipment Safety
Outside of safety, quality, reliability and local support, cost is often a major factor.
Cost does not equal purchase price alone. Total cost of ownership is a combination of purchase price, service cost as well as cost per (drying) batch.
Service cost is difficult to substantiate because manufacturers do not state such as part of their specification and marketing. Reason being the fact, that service cost heavily depends on use case. Any manufacturer statement would only ever be based on “ideal conditions”, so may well be far from reality.
What is relatively simple to calculate, is the cost per drying batch, based on power consumption and electricity prices.
The purchase price is a given – they are publicly advertised or can easily be obtained via supplier inquiry.
To calculate which choice offers lower cost we can do a break-even calculation. The break-even point is where the savings achieved through lower power consumption equals the cost difference.
What information is needed:
1. Power Consumption of the Freeze Dryer (in kWh)
The number used should represent the average power consumption of the freeze dryer over an entire run, not peak consumption nor minimum consumption. A freeze dryer typically consumes less power whilst freezing and in the early stage of a drying run, when heaters are off or set at low temperatures. In the later stage of the cycle the heaters are supplying a lot of energy. So, power consumption towards the end of a cycle is higher.
Some manufacturers state maximum current draw (in Amps) as part of their specification. In absence of such statements, the recommended circuit rating (in A) can be used as indicator. Amps can be converted to kWh at a known voltage.
For example, the Cryodry CD8 is rated at 8 Amp maximum current draw (including vacuum pump) which, in Australia at 240V equals 1,920W. A US brand XLarge model draws peak currents of 18A or 4,320W. Other North American brands require 20A circuits for their equivalent models suggesting 4,800W maximum draw.
However, average power consumption tends to be much less. The US brand reports 1,700W for their XLarge model. The CryoDry CD8 consumes 700W on average.
2. Power Consumption of the Vacuum Pump (in kWh)
Considerations for the vacuum pump are much the same as for the drier itself. Whatever the pump power consumption is must be added to the overall consumption calculation.
The US brand Premier XL pump rating is unknown. The CryoDry Duo6 pump is rated at 450W.
For simplicity of this example we disregard the pumps and assume stated machine consumptions include the recommended vacuum pump (which is likely the case).
3. Time per Run (in h)
To calculate the break-even we assume that each run takes 24 hours. For shorter runs, more runs will be needed to reach break-even, whilst longer runs will reduce the break-even count. Ultimately the break-even is a question of total run hours.
4. Electricity Cost (in kWh)
Typical Australian electricity rates are between 25 and 40 cents per khW. We will use 30 cents for our example calculation.
Summary:
When purchasing a freeze dryer, consideration ought to be given, not only to purchase price, but also to operation cost. Power consumption impacts directly on drying cost for each batch. Investing into a dryer that consumes less power will pay back – it is just a question of how many runs it will take.
Lower power consumption freeze dryers can also unlock freeze drier use in remote locations and to users who rely on solar and solar battery power. At average 0.7 kWh consumption and 16.8 kW per day, the CD8 can easily run off most solar power installations.