Plug Load Nuggets

Plug Loads: The Overlooked Energy Hog

Plug loads refer to energy used by equipment that is plugged into an outlet. In an office, key plug loads include computer and monitors, printers, and copiers. Plug loads can average approximately 30% of electricity use in office settings.

Plug loads as a share of overall building energy use is higher in energy efficient buildings. In minimally code-compliant office buildings, plug loads may account for up to 25% of total energy consumption. But in high efficiency buildings, plug loads may account for more than 50% of the total energy consumption.

Minimizing plug loads is a key challenge in the operation of an energy-efficient building. For example, California’s office plug loads consume more than 3,000 gigawatt hours annually, costing more than $400 million each year.

You can reduce plug loads by up to 50% at your facility by implementing simple, no cost and low cost strategies including power management and powering down equipment that is not in use. Federal facilities’ electricity use varies widely, depending on their size and the nature of their operations, but the average federal office facility spends $1.32 per square foot on electricity annually. If we assume plug loads account for 25%-35% of electricity use for federal facilities, than the average facility could save $0.17 - $0.23 per square foot annually by managing plug loads. This translates into savings of roughly $40,000 - $60,000 over five years for a facility of 50,000 square feet, or $200,000 to $300,000 over five years for a facility of 250,000 square feet.

Plug Loads: Low Hanging Fruit for Reducing Building Energy

Plug loads refer to energy used by equipment that is plugged into an outlet. In an office, key plug loads include computer and monitors, printers, and copiers. Plug loads as a share of overall building energy use is higher in energy efficient buildings. In minimally code-compliant office buildings, plug loads may account for up to 25% of total energy consumption. But in high efficiency buildings, plug loads may account for more than 50% of the total energy consumption.

Plug loads are a key challenge in operating an energy efficient building. They are also a promising opportunity for cost-effective energy reduction. You can reduce plug loads by up to 50% at your facility by implementing simple, no cost and low cost strategies including power management and powering down equipment that is not in use. Investing in these no cost and low cost strategies can forestall or minimize the need to invest in renewable energy sources to meet net zero energy targets for federal facilities.

Federal facilities’ electricity use varies widely, depending on their size and the nature of their operations, but the average federal office facility spends $1.32 per square foot on electricity annually. If we assume plug loads account for 25%-35% of electricity use for federal facilities, than the average facility could save $0.17 - $0.23 per square foot annually by managing plug loads. This translates into savings of roughly $40,000 - $60,000 over five years for a facility of 50,000 square feet, or $200,000 to $300,000 over five years for a facility of 250,000 square feet. 

The Power of Power Management

Energy Star computers have factory installed power management features, but they are often disabled by administrators and users. Computers in particular are often left in active mode even when they are not in use.

By enabling the power management features, you can reduce computer energy use during non-business hours by 60% at no cost. The average desktop computer without power management enabled uses nearly 500 kWh annually. Applying the average electricity rate paid by the federal government, in a federal facility with 500 computers, this reduction in computer energy use during non-business hours would save $7,500 annually or $37,500 over five years. Because using power management is a no-cost strategy, these savings pay for themselves immediately. Power management features are important to enable in other office equipment as well. Enabling power management in copiers can save up to 90% of energy use in non-business hours, and up to 90% for laser printers.

Night Time is the Right Time (to Power Down Your Office Equipment)

While offices and buildings are becoming more energy-efficient in general, the trend in powering down office equipment is going in the wrong direction. Computers and other devices are less likely to be powered down when not in use now than they were a few years ago.

Monitors, printers, and copiers should always be turned off at night. In addition, facility managers should work with their IT departments to allow and encourage occupants to power down their computers at night. By powering down office equipment, a federal facility with 500 workstations could save $25,000 annually or $125,000 over five years.

The Energy Star program offers free technical assistance to federal facilities and IT departments to overcome any technical barriers to powering down (such as scheduling software updates and other maintenance during nighttime hours).

Installing Timer Plug Strips to Save Energy (and Money)

Plug strips can save energy from computers and other office equipment by automatically powering down devices when not in use. However, not all plug strips are equal. As a general rule, to maximize energy savings, you should buy timer plug strips (i.e., plug strips that operate on a pre-set schedule) rather than other types of plug strips.

Timer plug strips pay for themselves through energy savings in about 3.5 years. While they cost more initially than other plug strips, the savings over time mean they are a good value in terms of lifecycle cost. Occupancy and load-sensing plug strips can also save energy, but their payback period is much longer.

You can find plug strips with energy saving features through multiple GSA Schedules and on GSA Advantage.

The Energy Lowdown on Laptops

Laptops outperform desktops from an energy use perspective. Laptops use 78% less energy than desktops on average. Also, users are more likely to keep power management features enabled on laptops than on desktops.

The average laptop use 58 kWh per year compared to 266 kWh for the average desktop. Applying the average electricity rate paid by the federal government, each laptop used by the federal government saves about $20DL1 per year. This means that if your facility purchases 200 new personal computers this year, you can save $4,000 in energy costs in one year from buying 200 laptops instead of desktops, and $20,000 over 5 years.

Be sure to specify Energy Star products when purchasing laptops.

What Gets Measured Gets Managed: Metering Your Plug Loads

Related Topics

Energy Efficiency

Energy efficiency is a comparison of the amount of energy used compared to the amount of output produced. In the built environment, this means using the least amount of energy (electricity, natural gas, etc.) to operate a facility appropriately. Steps that can help a building run efficiently include: ensuring there are no air leaks, using sensors or timers to ensure the building isn’t operating when vacant, and using energy-efficient equipment.

Plug Load Control

Plug load control comes in two basic forms. Energy savings are achieved when the device is either transitioned to a low-power state, or it is de-energized to eliminate the power draw. Both can be executed either manually or automatically. A low-power state is between a de-energized state and a ready-to-use state. This includes standby, sleep, and hibernate modes as well as any “off” state that has a parasitic power draw. A de-energized state is when electricity is not being provided to the device. This is analogous to physically unplugging a device’s power cord from a standard electrical outlet.

The most prevalent plug load contral strategies include:

• Manual Control: Most plug-loads can be manually powered down with built-in power buttons, shutdown procedures, or a control device that energizes and de-energizes electrical outlets based only on manual input. The effectiveness of manual control depends entirely on user behavior and should be implemented only if no other methods apply.
• Automatic Low-Power State: The first, and in some cases most effective, control method is a built-in, automatic low-power state functionality such as standby or sleep. Some manufacturers include this functionality to reduce energy consumption of idle devices. Internal processes monitor idle time, and when the device has been in an idle state for a given period, it will power down to a low-power state.
• Schedule Timer Control Device: Certain plug-loads have predictable load profiles. These devices are used during the same times each day or at regular intervals. A scheduling-control device can effectively manage a predictable plug-load. It applies user-programmed schedules to de-energize the plug-load to match its use pattern and energize the plug-load so that it is ready for use at the time when it is required.
• Load-Sensing Control Device: Plug loads may have a primary-secondary relationship. A primary device, such as a computer, operates independently of other (slave) devices. A secondary device, such as a monitor or other peripheral, depends on the operation of other (master) devices. A load-sensing control device should be implemented for such a relationship. It automatically energizes and de-energizes secondary devices based on the “sensed” power load of the primary device(s). Whenever the primary device goes into a power state below a given threshold, the load-sensing control can power down the secondary devices. The sensed (primary) load is typically an electrical outlet or an auxiliary port (e.g., universal serial bus (USB) in the case of a computer).
• Occupancy-Control Device: Occupancy control can save a great deal of energy as it energizes plug-loads only when users are present and de-energizes them when the space is vacant. This approach pinpoints the main source of wasted energy during non-business hours and reduces wasted energy during business hours. However, the largest drawback is that occupancy controlled devices may energize and de-energize outlets at inappropriate times.
• Manual-On, Vacancy-Off Control Device: A manual-on, vacancy-off control device is a slight modification of the occupancy-control device. It energizes a plug-load when it receives manual input from a user and de-energizes the plug-load automatically based on lack of occupancy. This control should be implemented for plug-loads that are needed only when users are present (e.g., task lights, monitors, and laptops).

Plug Loads

Plug loads are the electrical loads in a building due to the various devices that are plugged into receptacles. Examples of plug-load devices include, but are not limited to, the following: computers, printers, task lights, vending machines, desk fans, etc. Recent research shows that desk-based technologies and electronics in office settings can consume significant amounts of energy that are often not taken into account in energy monitoring and reduction strategies. These technologies are generally under the control of individual workers rather than centrally operated, making plug loads "orphans." They are usually not managed until there is a plan in place to do so. Workstation plug-loads are not the only challenge. Electronic equipment in shared spaces—such as print/copy rooms and break rooms—can also be a significant energy consumer, and with no one person responsible for turning it off, shared equipment is often left “on” indefinitely. 

Plug loads as a share of overall building energy use is higher in energy efficient buildings. In minimally code-compliant office buildings, plug loads may account for up to 25% of total energy consumption. But in high efficiency buildings, plug loads may account for more than 50% of the total energy consumption.