Pathways to commercial building plug and process load efficiency and control

Reduction strategies refer to the occupant-enacted, deliberate reduction or shutdown of non-essential PPLs when not in use, such as during the building’s unoccupied hours. Strategies in this category include occupant awareness programs, such as training sessions and informational campaigns to educate occupants about the energy impact of PPLs. Communication and signage reminding occupants to turn off PPLs when not in use are often part of these programs, as well as PPL champions that organize and promote PPL energy-saving initiatives. Often, these programs are tied to the implementation of a PPL control technology (Jenkins et al., 2019). Also in this category are gamification and incentive programs that recognize occupants for energy-saving behaviors, which have been shown to be effective at reducing energy consumption and developing energy stewards (Hafer et al., 2018).

Another strategy involves procuring and installing energy-efficient PPLs. As devices and equipment become inherently more efficient through manufacturer-implemented improvements, replacing PPLs at the end of their life with more efficient models presents an opportunity for savings. Many PPLs now come equipped with low-power modes or sleep settings. Ensuring these features are enabled during installation or commissioning can further enhance energy savings.

There are several types of PPL control technologies, also referred to as plug load management (PLM) or plug load control (PLC) technologies, all of which cut power to PPL devices automatically to reduce standby energy consumption. Advanced power strips (APSs) are separate power strips that can be controlled manually or with sensors to shut off power to specific PPLs (Fig. 1). There are many APS providers and varieties that come with different capabilities to meet different needs. For example, depending on the APS purchased, there may be wireless transmission and energy monitoring capability (Earle & Sparn, 2012). This technology is most effective for controlling specific devices, rather than the whole building, and allows the linking of multiple appliances under the same control.

There are two technologies used as PLM systems. The first are smart outlets, which are plugged into existing outlets and measure plug load energy usage (Fig. 2). They wirelessly transmit data and can be controlled to turn power on or off. This technology is effective for automatically controlling devices based on a schedule and understanding full building and device-specific energy usage and behavior. Often, data can be accessed via an online dashboard or smartphone application. Additionally, some smart outlet systems use machine learning algorithms that can predict schedules (Trenbath et al., 2020), while others can apply controls based on occupancy sensor data. There are buttons built directly into smart outlets that allow the in-room user to instantaneously override the control and turn on power delivery through the outlet.

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Automatic receptacle controls (ARCs) are also used as PLM systems, and they automatically turn off power to receptacles using signals from occupancy sensors, control schedules, or other building systems (Fig. 3). This technology meets energy code requirements specified in ASHRAE Standard 90.1, the International Energy Conservation Code (IECC), and California Title 24. They are best suited for plug-in devices that only need to be operational when the building is occupied. Like smart outlets, there are often buttons built directly into ARCs for users to override control and turn on power through the receptacle. Manufacturers offer multiple ARC configurations for controlling either one or both outlets in a duplex ARC.

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Integration of PPL control systems with other building controls may provide increased energy savings compared to PLC alone, and a few of these PPL integration projects have emerged over the past 3-5 years. PPL control technologies are often good candidates for integration with lighting control systems because they can leverage occupancy sensor data that is already employed by the lighting control system (Davalos et al., 2020; Integrated Controls for Plug Loads and Lighting Systems, 2022). Integration of PPL control technologies with the building automation system (BAS) is even less common. This technology is actively being researched, with demonstration of integration between smart outlets and BAS at a university campus showing 66% energy savings (Chia et al., 2023).

To date, most PLC technologies cut off the power supply to PPLs at the outlet to save energy. However, not all devices are suitable for on/off controls provided by these technologies. This is due to several factors, such as the need to maintain network connection or the risk of component damage if powered off at the outlet. For PPLs where on/off controls are not suitable, sleep settings can be a viable option for achieving energy savings.

There have been limited studies conducted on the adoption of PPL efficiency and control. Tekler et al. conducted focus groups and online surveys to investigate adoption of PLM systems in office buildings (Tekler et al., 2021). Among the concerns expressed in the study, participants were worried that an automated PLM system would be difficult to use, may turn off their plug loads when they are in use, and may affect their current workflow. Study participants selected intuitive, easy-to-use, and easy-to-integrate with other management systems as the attributes of an ideal PLM system.

Occupant behavior and engagement have been identified as key factors for PLM system adoption in several studies. A PLM system field study published by Kandt and Langner found that building occupants became frustrated with the PLM system due to schedule controls that were incompatible with their device needs and unplugged the PLM devices to override controls, leading to decreased energy savings and unfavorable payback. The researchers cited operations staff engagement with both the PLM system and building occupants as a key contributor to the success of PLM system implementation (Kandt & Langner, 2019). Hafer et al. implemented a PLM system with active occupant engagement technology to enable participants to view their consumption, remotely control devices, set schedules, and engage in a game (Hafer et al., 2018). The results showed 21% savings in average daily consumption, and demonstrated that occupant engagement was an effective strategy when paired with a PLM system.

There are limited, formal studies that investigate or document the influence of occupant behavior on PPL efficiency and control adoption. Anecdotally, speaking with building owners and operators we have learned that occupant pushback has historically been a significant barrier to adoption of control technologies and reduction strategies. There is more literature available (see Section “Commercial building energy efficiency adoption”) on the impact of occupant behavior on technology adoption in commercial buildings, in general. Though they do not explicitly investigate or describe PPL efficiency and control, their findings may be applicable to PPL adoption.

As noted in the previous section, few studies have explored the adoption of PPL efficiency and control measures. This section examines the factors influencing the adoption of efficiency practices and technologies in commercial buildings, which may also affect PPL efficiency and control implementation.

As is the case with PPLs, occupant behavior is also a factor in non-PPL efficiency and control technology adoption, as well as in commercial building energy efficiency in general. Zhang et al. estimated the whole-building energy-saving potential of occupant behavior in commercial buildings to be 5-30% (Zhang et al., 2018). Like PPLs, eco-feedback and gamification can be effective methods to influence occupant behavior to achieve greater energy efficiency (Paone & Bacher, 2018). Technology design can be a factor in adoption as non-intuitive design can impede occupants’ ability to use the technology, as was the case for thermostats in an office field study (Karjalainen & Koistinen, 2007). Additionally, so-called “robust” design techniques make commercial building energy consumption less sensitive to occupant behavior, and do not require building occupants to understand how the building’s systems work to use them properly. An energy simulation study by Karjalainen showed that a “careless user” consumes 75-79% less energy in buildings with robust design solutions compared to ordinary design solutions. They also argued that the design of energy-efficient buildings could benefit from using a realistic view of occupant behavior (i.e., reducing the burden on occupants to understand building operations or take energy-saving actions) (Karjalainen, 2016). Furthermore, there is a need for occupant data, including behavior and patterns, to inform building design and modeling (Ahn & Park, 2016; Delzendeh et al., 2017).

Several other studies have investigated the non-occupant behavior factors impacting energy efficiency technology adoption in commercial buildings. Hanus et al. found that owners and managers prioritize corporate social responsibility (CSR) when making energy efficiency decisions, whereas experts, such as consultants, do not emphasize CSR and are more concerned with costs, such as energy and labor costs, and retaining tenants (Hanus et al., 2018). Papagiannidis and Marikyan found that labor force skills, the readiness of organizational structure, and compatibility of existing technological infrastructure with smart devices impact smart technology adoption. In addition, they found that a company’s culture can influence whether they make changes toward more intelligent buildings, and that company management may believe smart technologies pose security, financial, or other threats (Papagiannidis & Marikyan, 2020). Hanus et al. identified four key non-technical barriers to energy efficiency investment decision-making in data centers: low energy efficiency saliency in information technology (IT) staff, technical risk aversion, lack of knowledge, and time discounting. Proposed interventions to address these barriers include increasing awareness of energy-efficient products, technologies, and services; establishing an energy efficiency champion; and demonstrating a multitude of benefits from energy efficiency measures (Hanus et al., 2023). Andrews and Krogmann found newer, larger, more energy-intensive, owner-occupied buildings to be those most likely to adopt energy-efficient heating, cooling, window, and lighting technologies because they can afford installation costs (Andrews & Krogmann, 2009). They cite the split-incentive problem as a key factor affecting adoption–rental buildings are less likely to adopt energy–efficient technologies. The split-incentive problem (also referred to as the principal-agent problem) in commercial buildings refers to a relationship between landlord and tenant in traditional leasing agreements in which capital improvements that yield energy savings result in one party paying for the improvements while the other party receives the benefit of reduced utility costs. This is a well-documented, international problem in both the commercial and residential sectors, and there are numerous proposed solutions, including green lease structures, regulatory solutions like minimum performance standards or green building codes, disclosure of energy performance during the buying and leasing process, building sub-metering, and financial incentives designed for renters (Bird & Hernández, 2012; Joint Research Centre (European Commission) et al., 2017; Miller, 2010; White et al., 2020).

Policy plays an important role in the adoption of building energy efficiency practices and technologies, though policy decisions are out of scope of this paper. Ensuring a well-functioning policy mix is especially important (Rosenow et al., 2016). There are generally three categories for policies: mandatory, voluntary, and economic incentives. Each has its own challenges: mandatory policies require resources to enforce, voluntary policies are highly dependent on the enthusiasm of stakeholders to be effective, and economic incentives require consistent funding (Shen et al., 2016). Björklund et al. identified policy opportunities for the transition to energy-efficient and zero-carbon buildings in the European Union (EU), finding that voluntary policy instruments should be complemented by mandatory instruments to promote policy uptake. Furthermore, new policy instruments tend to be developed most commonly at the regional/local level, and there is limited diffusion and coordination between governance levels, thus limiting sharing of best practices within multilevel systems (Björklund et al., 2023). Additionally, Mills found that a more focused and coherent policy strategy may improve the adoption of residential heat pump water heaters in the U.S. (Mills, 2022).

Building energy codes, like ASHRAE 90.1, IECC and Title 24, also play an important role in the adoption of energy efficiency practices and technologies. Schwartz and Krarti found code requirements to be among the common characteristics for highly adopted sustainable energy technologies in the U.S. residential building sector (Schwartz & Krarti, 2022). Codes have also been found to drive product innovation (Vaughan & Turner, 2013) and can increase energy-efficient products available on the market.

There are several formal theories that describe the adoption of new behaviors and technologies. Rogers’ Diffusion of Innovation (DOI) theory explains how an idea or product diffuses over time, and establishes five adopter categories: Innovators, early adopters, early majority, late majority, and laggards.When promoting an innovation or product, it is important to consider your audience with regards to these adopter categories. Rogers’ DOI also proposes five characteristics that make a technology more or less readily adoptable: Relative advantage, compatibility, complexity, trialability, and observability (Rogers Everett, 1962). These characteristics have been used to explain the adoption of many energy efficiency technology measures, and researchers have published additions to Rogers’ key characteristics (Outcault et al., 2022).

The Unified Theory of Acceptance and Use of Technology (UTAUT) explains behavior related to stakeholder expectation and buy-in of new technologies with four key constructs (Venkatesh et al., 2003):Cowan and Daim found parallels between UTAUT and the adoption of energy-efficient lighting (LED) technology. Namely, future energy price expectancies, actual savings results, and ease of energy savings, as well as social influences such as perceptions of environmental friendliness, policies, incentives and educational programs are key factors influencing adoption (Cowan & Daim, 2013).

Although there is no existing literature on the application of Rogers’ DOI or the UTAUT to PPL technology adoption, these theories have been utilized for other energy efficiency measures and could similarly be applied to PPLs.

Several factors currently drive implementation of PPL efficiency and control. Most common was energy-efficient procurement strategies. One facility manager participant said that all vending machines in their facility were required to be ENERGY STAR-certified: “Most of vending is third-party contract. These must be ENERGY STAR.” Another participant said all new equipment is required to be energy efficient: “If new equipment is procured, ENERGY STAR or efficient equipment is procured.” Several participants mentioned that PPLs are becoming a higher priority for reduction: “Other low-hanging fruit getting done makes PPL more important,” and “As buildings become more efficient, PPLs are larger part of our energy pie. [We] will eventually need to reduce PPLs as we drive down future energy [and] GHGs.”

Based on participant feedback, it is also common for commercial buildings to be sub-metered: “[We] sub-meter loads as best as possible to evaluate better technologies for control or load reduction.” One building owner participant has required sub-metering on their tenant spaces specifically for PPL monitoring: “[We] have implemented sub-metering as a tenant requirement to allow for visibility of plug loads.” Another participant identified monitoring loads as an area of improvement: “[Our loads] are not monitored. This would be an area of improvement.” Several participants also noted they are not currently monitoring their PPLs but did not make any indication as to whether they would in the future.

When it comes to “who” is driving the implementation, one design engineer participant said it is the client/building owner: “[The] client has a goal in mind, and we work with them to get to that goal.” Another said it depends, and that design engineers play a role by providing energy-efficient options: “[The] client/owner decides, in some cases [the] architect. Designers suggest energy-efficient options to explore for projects.” Another said, “The brokers really drive the decision. If [the client] needs to position the building on the market, they always ask the brokers in terms of what we are seeing on the market.”

Study participants are currently reducing PPL energy consumption via plug load control (PLC) and occupant engagement. PLC technologies mentioned include schedule-based and occupancy-based control ARCs, and smart outlets. Several participants have used or are currently using time clock-based controls: “[Using] time clock [automatic receptacle control] (ARC) is the majority [of PPL control processes],” and “Select building receptacles are on a time clock.” Others have experience using occupancy-based PLC: “[We use] occupancy-based power strips,” and “Computer monitor and task lamp plug loads [are] controlled by occupancy sensors.” One participant said that in addition to occupancy-based control, they have used smart plugs: “Experience with smart plugs and have some plug loads in our building that are connected to occupancy sensors.” One facility manager participant has experience with integrated PLC: “BAS controls and lighting controls that control plug loads with occupancy sensors.”

Several participants have engaged building occupants to promote energy efficiency: “[We have conducted an] educational campaign for residents like fridge magnets – guidance and social media blast for energy efficiency.” Another building owner participant mentioned educating occupants about a PLC system in the buildings: “A net-zero energy building has a system [where] if computer is not docked, the [occupants] do not have power to the desk plug loads and task lighting. Information was distributed through the property manager association to tenants.”

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While study participants cited load monitoring as a current driver for PPL efficiency and control, the data is primarily being collected for all building end uses through sub-metering: “[I have] experience with sub-meters and pulling those into analytics software but rarely is it just plug loads.” For participants sub-metering their building(s) at the end-use level, some are not currently using this information to make decisions: “[We have been] increasing our sub-metering to get a better idea of usage and cost of end-use loads, but not currently doing a whole lot to manage and control these devices.” However, a minority of the participants are utilizing sub-metered data: “[We] sub-metered PPLs for buildings including IT rooms, data centers, lab equipment, data equipment, etc., [and] conducted studies to analyze tenant versus landlord loads.”

Uncertainty of savings was identified as a barrier to commercial building energy efficiency adoption by Hanus et al. (2018). This was also a significant barrier to PPL efficiency and control adoption we identified by speaking with study participants. One of the major pathways to address the barrier associated with the lack of available financial data is to conduct rigorous and widespread technology evaluations in real commercial buildings. Once installed, operated, and monitored, independent evaluators or measurement and verification (M&V) specialists should analyze the resulting data from these PPL technologies. Guidelines and M&V frameworks such as those from the International Performance Measurement and Verification Protocol (IPMVP) should be applied to accurately determine energy consumption and savings. To address the next set of awareness barriers and promote effective PPL efficiency solutions, evaluators should disseminate the assessed technical and financial data, operational best practices, and lessons learned. Conducting training sessions, imparting knowledge gained through successful case studies (written and webinar format), simple commissioning how-to guides, and control technology campaigns for various organizations can lead to awareness among the occupants and decision-makers.

Several studies we reviewed found occupant awareness and engagement to be a key factor in PPL energy reduction (Kandt & Langner, 2019; Hafer et al., 2018; Tekler et al., 2021; Zhang et al., 2018). From our interviews and the workshop, we found that because PPLs are a highly occupant-dependent end use, mere PPL control technology installation in a commercial building is not effective and requires decision-makers and occupants to learn how to work effectively with the technology to achieve maximum benefit. The performance expectancy and effort expectancy are not being communicated to the occupants. Including material for engaging and educating occupants in the case studies could address this barrier and result in successful implementation.

We did not find the type and features of the PPL control technologies to be a major factor in adoption – technology features were only mentioned once in the interviews. This emphasizes the importance of occupant awareness and engagement with the control technologies for uptake.

Increasing the number of available case studies on PPL efficiency and control implementations, as well as disseminating best practices, is essential to overcoming key barriers in the commercial building industry. By showcasing real-world examples and providing transparent data, these case studies can help reduce uncertainty around savings, enhance awareness, and promote broader adoption of PPL technologies across diverse building types.

Increasing funding opportunities, such as incentives and rebate programs, is critical to enabling the widespread adoption of PPL efficiency and control measures in commercial buildings. Multiple studies found availability of funding to be a significant factor for the implementation of commercial building efficiency technologies (Hanus et al., 2018; Andrews & Krogmann, 2009). In this study, we spoke with commercial building owners and occupants who mentioned there being a lack of funding for PPL control technology implementation. The split-incentive problem was a barrier identified by Andrews and Krogmann (2009) and Hanus et al. (2023). Participants in our study pointed to the split-incentive problem as a barrier to PPL efficiency and control adoption, as well. The split-incentive problem is a known issue in traditional commercial building lease structures that affects energy efficiency projects. A lot is being done to address the split-incentive problem, including green leases, and these efforts will help remove barriers for PPL efficiency and control implementation in commercial buildings. Green leasing, also known as energy-aligned, energy-efficient, or high-performance leasing, is the practice of equitably realigning the costs and benefits of energy and water efficiency investments for landlords and tenants (White et al., 2020).

Furthermore, increasing the availability of PPL-related incentives, including packaged incentives with other energy efficiency measures and rebate programs could help commercial buildings overcome these funding barriers, as well as promote implementations with favorable payback. This, in turn, will increase the number of available case studies.

Literature shows there is a need for commercial building occupant data to inform and improve building design and modeling (Ahn & Park, 2016; Delzendeh et al., 2017). Beyond that, our study reveals that design and modeling will also benefit from comprehensive PPL baseline consumption data, and will be important for addressing the current data gaps that hinder the adoption of PPL efficiency and control measures. Several participants cited lack of available data as a barrier to PPL efficiency and control uptake. Participants mentioned that scarcity of quality and revised technical data available to designers and facility/sustainability managers often leads to excessive and overdesigned infrastructure. A rigorous compilation of updated PPL baseline and peak consumption for the U.S. commercial building stock could lead to the generation of the technical data needed for designers and building energy modelers. This accurate PPL load data can also help efficient design of other building end uses like HVAC and lighting.

Study participants focused on inclusion of PPL monitoring and reduction measures in commercial building energy codes as an important factor for driving widespread adoption of PPL control technologies and ensuring long-term energy efficiency in the sector. Participants mentioned codes and regulations as key drivers of getting various PPL control technologies into commercial buildings. While Hanus et al. also identified energy codes as a crucial factor for adoption of commercial building technologies, this insight is relatively novel in the context of PPL literature (Hanus et al., 2018).

Additionally, successful case studies with favorable financial performance will encourage code bodies to continue to include effective PPL monitoring and controls in energy codes.

Company goals were mentioned as a key contributor to the success of PLM system implementation in commercial buildings, and companies should continue to establish goals related to energy efficiency and emissions reductions, such as ESG goals, SDGs, and emissions targets. Some study participants mentioned PPL efficiency and control implementation as being the responsibility of another stakeholder group, and that lack of implementation is the result of lack of action by the other stakeholders. This deferred responsibility can be influenced by gaining buy-in from key stakeholders and critical implementors (e.g., a building’s cybersecurity and IT teams, electricians) through things like company goals. Additionally, establishing a PPL champion to initiate the PPL control and reduction procurement and implementation process can help get the necessary stakeholders on board.

Organizations with ESG goals, SDGs, and emissions targets and/or strong culture around environmental stewardship may be early adopters of PPL efficiency and control technologies and strategies. These buildings may be best suited to generate initial case studies that can help members of the early majority and late majority adopter categories make the business case for implementation. Additionally, effectively communicating these goals to employees and building occupants can create the social influence needed to promote proper engagement with the technology or strategy.