1 centimeter of ice layer in your freezer costs you 30% extra power, physically measurable. The ice crust insulates, the compressor works longer. 15 minutes defrosting monthly saves you at least 200 € in power costs over 5 years.
Step by step
When water vapor (from your food or door openings) hits cold surfaces (-18 °C), it freezes into ice, an insulating layer. This layer reduces heat contact between evaporator and contents, the motor (compressor) must run longer to maintain the same temperature. 1 mm ice = 0.5% more consumption, 1 cm = 30% more. In older devices without automatic defrost this is the biggest efficiency killer.
Source: Deutsche Energie-Agentur (dena), ice layer in freezer significantly increases power consumption
Step by step
- 1. When to defrost? Rule: from 0.5 cm iceOpen your freezer and look in: if the inside has a frost layer or visible ice chunks, it's time. Ideally monthly, at least once per quarter.
- 2. Remove frozen goods, temporarily into ice box if availableSmall portions can sit 10-20 min at room temperature, cold chain holds that long. Larger amounts in an insulated box with ice packs.
- 3. Switch off powerSwitch off or pull plug. Important: make sure all doors are closed (no open freezer parts anymore).
- 4. Let water drain + scrape surfaceIce thaws slowly. Place a flat container under the drain opening (bottom back, usually a small hole). Scrape loose ice chunks with a plastic ice scraper or wooden spatula, NOT metal (damages surfaces).
- 5. Dry interiorWipe remaining moisture with a towel or cotton cloth. Prevents new ice from forming immediately.
- 6. Plug back inAfter 30-45 min the defrost is complete. Power back on, frozen goods back in, close door. Device needs ~30 min to reach -18 °C again.
Worked example
Before: Freezer with 0.8 cm ice layer, not defrosted for 5 days: compressor runs 60% of the time instead of normal 40% = +50% power draw. A 150-kWh/year device becomes 225 kWh/year = 56 € instead of normally 37.50 € = 18.50 € extra per year.
After: With monthly defrost routine (max 0.2 cm ice): compressor runs normal 40% = 150 kWh/year = 37.50 €. Savings = 18.50 € per year.