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Do We Really Need Another Clock in the Kitchen?

Richard Fassler -June 25, 2012

Earlier this year, the U.S. Department of Energy published a notification (link supplied at the end of this blog) to propose limiting the energy consumption of one of my favorite kitchen appliances – the microwave oven. But the DOE’s focus isn’t on the energy consumed while the microwave is heating food; instead,it wants to limit the power consumed while the microwave is doing nothing (i.e. in standby or off mode).

OK, this isn’t my first “energy vampire” rodeo… this has been an on-going discussion with electronic consumer products like TVs and set-top boxes that currently are required to stay in an “elevated”  standby mode in order to allow software and firmware updates. But why shouldn’t microwave ovens be allowed to turn off or at least go into a deep-sleep, consuming close to zero watts when they’re not heating something up? The reality is that they never get to turn off and instead consume a surprising amount while waiting to be used.

The DOE looked at standby power consumption for two product classes of ovens:

  • Microwave-Only Ovens and Countertop Combination Microwave Ovens
  • Built-in and Over-the-Range Combination Microwave Ovens

Unit testing showed that the standby power consumption for microwave-only and countertop combination ovens ranged from 1.2 W to 4.7 W. Meanwhile, built-in and over-the-range combination ovens consumed 4 W to almost 9 W of power while in standby. The features driving the high levels of standby power included cooking sensors, display technologies (including clocks), and control strategies (control boards) to turn off power to components during standby. The DOE observed that most microwave ovens available in the U.S. did not include options that could cost-effectively reduce power consumption, including a mechanical on-off switch (to allow the oven to go into an off mode) or a user control that could turn the display (clock) off when not in use.

Table 1 below shows the DOE’s proposed limits. If approved, the compliance date will be three years from the standard’s finalization date.

Table 1.Proposed Standby Power Limits for Microwave Ovens

Product Class

Proposed Energy

Conservation Standards

Microwave-only ovens and countertop combination microwave ovens

Maximum standby power = 1.0 W

Built-in and over-the-range combination microwave ovens

Maximum standby power = 2.2 W

Source: U.S. DOE

Stakeholders have been asked to comment on whether the use of alternate technology options, such as switching power supplies, clock display controls, or automatic power down could be employed in future models.

Adding a mechanism that allows users to turn off the clock display seems like a reasonable and easy first step to reducing microwave oven standby energy waste. 

For more information, including the Supplemental Notices of Proposed Rulemaking, test procedure, stakeholder meeting presentation, and more, go to: http://www1.eere.energy.gov/buildings/appliance_standards/residential/cooking_products.html

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