Miscellaneous electric load
Miscellaneous electric loads (MELs) in buildings are electric loads resulting from electronic devices not responsible for space heating, cooling, water heating, or lighting. MELs are produced by hard-wired and “plug-in” electrical devices, including home entertainment centers, kitchen electronics such as microwaves and toaster ovens, bath items such as hair dryers and electric hot tubs, and others such as security systems and ceiling fans. MELs are gaining greater importance as home electronics become more sophisticated and more widespread, and miscellaneous electric use can only be expected to rise.
Miscellaneous electric use includes a diverse collection of electronics, such as power adapters, pool pumps, computer equipment, televisions, door bells, phone/fax machines, and many others. MELs usually do not include major appliances such as refrigerators, stoves, dryers, etc. Although each device may draw a small amount of power, the large and steadily increasing number of devices can use a significant portion of a home’s energy. In the United States, MELs comprise nearly one quarter of residential energy use, larger than either heating or cooling energy end-use. In low-energy houses, this percentage increases dramatically, because MELs are often ignored while increasing whole-house efficiency.
On average, home entertainment equipment, including televisions, audio equipment, and computers, make up about half of the total MELs in a United States home. About 13 percent of MELs come from devices in standby mode.
Significance to zero-energy buildings
MELs can be lowered by using fewer electronic devices, choosing more efficient electronics (for example, Energy Star appliances), modifying occupant behavior and managing standby power. Still, MELs are a significant obstacle in creating zero-energy buildings. Heating, cooling and water heating energy loads can be reduced by improvements to the building envelope, HVAC and water heating equipment, and air distribution system. MELs are more elusive, however, because of their diversity. Many miscellaneous electric devices that can be found in a large fraction of houses are smaller—for example toasters, televisions and internet routers, while larger power draws, such as well pumps or waterbed heaters, are present in only a small fraction of houses. Such variety makes it hard to find a systematic method of reducing MELs. If MELs cannot be reduced, the only way to counter them is with larger (and thus more costly) solar arrays or other electricity generation methods.
Energy feedback devices
One reason MELs are difficult to reduce is because the use of small electric devices are controlled directly by a building’s inhabitants. One way to reduce MELs is by the use of energy feedback devices which report real-time energy use to a house’s occupants. The use of these devices has been tested in numerous studies which suggest whole-house savings of 5%-15%. With recent advances in technology, energy feedback devices can be purchased for $100–$150. Feedback devices allow people to identify and reduce standby power and as well as cut back on unnecessary power draws. In addition, occupants can see the effects of running pool pumps/heaters, supplemental space heaters, air conditioners, etc. Energy feedback devices can further assist zero energy buildings, where it is desirable to align electric loads with photovoltaic panel output.
- Roth, K., McKenney, K., Brodrick, J. "Small Devices, Big Loads." ASHRAE Journal. Vol. 60 No. 6. June 2008.
- R. Hendron and M. Eastment, Development of an Energy-Savings Calculation Methodology for Residential Miscellaneous Electric Loads”, ACEEE Conference Paper, August 2006, pp.1, 4.
- National Renewable Energy Laboratory, “Final Report: Potential Savings in Miscellaneous Electric Loads from Use of Next Generation Appliances” 29 March 2007, pp. 14.
- Darby, Sarah, 2000, "Making it obvious: designing feedback into energy consumption," Proceedings, 2nd International Conference on Energy Efficiency in Household Appliances and Lighting. Italian Association of Energy Economists, Naples, 2000. pp. 7
- Parker, D., Hoak, D., Cummings, J., “Pilot Evaluation of Energy Savings from Residential Energy Demand Feedback Devices,” Florida Solar Energy Center, January 2008.
- Parker, D., Hoak, D., “How Much Energy Are We Using? Potential of Residential Energy Feedback Devices,” Proceedings of the ACEEE 2006 Summer Study on Energy Efficiency in Buildings, August 2006, pp. 2.