Cut Power Costs - Which System Best Suits Your Facility?
The Smithsonian Institution's 11 major facilities in Washington, D.C., comprise around four million square feet of floor space. Normal operations include scores of retailers and concessionaires who consume mass quantities of electricity, gas and water while serving tens of thousands of visitors daily. Until recently, energy consumption was tracked by a master meter at the main utility service entrance of each building and costs allocated to tenants and departments on a square-footage basis. However, to more accurately allocate energy costs, facility managers installed a full-featured submetering system to integrate electrical, water and gas consumption into a single database that would allow for a more accurate assessment of actual use.
Through submetering, ongoing energy monitoring revealed that the lease tenants were supposedly underpaying for the energy services they were actually using. The system allowed managers to then reallocate an estimated US$1.7 million in energy costs that would have otherwise been paid for with federal tax dollars. Annual savings through submetering are expected to continue their upward trend due to periodic utility rate hikes and additional consumption from a new facility that recently opened. At the bottom line, the US$100K investment in submetering hardware and software generated a return on investment of about three months after the first quarterly utility billing cycle.
This is one dramatic example of how rising power costs, tightening budgets and other operational considerations are making energy resource management more important than ever for today's commercial building owners and operators. However, the level of profiling needed by many energy consumers is simply unobtainable using the standard utility meter at the main service entrance. This is why submeters continue to be used as first-level data-gathering tools that can save thousands of dollars in reduced annual energy costs.
First introduced in the early 1980s, submeters are metering devices, with monitoring capability, that are installed on the facility side of the master meter to provide:
- Usage analysis and identify peak demand levels
- Time-of-use metering of electricity, gas, water, steam, BTUs and other energy sources
- Fair and equitable cost allocation for tenant billing
- Measurement, verification and benchmarking of kW/kWh for energy initiatives
- Load comparisons
- Threshold alarming and notification
- Multi-site load aggregation and real-time historical monitoring of energy consumption patterns for negotiating lower energy rates
Three Types of Submeters
The table shown compares the three main types of submeters on the market. Socket-style meters are commonly used in multi-tenant residential facilities where an existing base of utility sockets is being upgraded to a master meter arrangement with the serving utility-possibly driven by the desire to choose providers. In this scenario, the meter size is 200A or less, which calls for a feed-through meter, not a current transformer-type. CT-style socket meters are used with loads of 400A and above. They may be specified in commercial applications but require excessive space in the electrical room for the CT cabinets and meter bases. Also, the extra space requirement impacts the useful rental square footage, an undesirable condition in commercial applications.
The third type is the electronic submeter, a non-socket device that provides clear advantages over the previous two, as shown in the table. Of special importance is the latter's use of low-voltage, split-core current sensors that installers can connect without powering down the measured load - making for a quicker, simpler and safer installation.
Recently, submeter manufacturers like E-Mon have answered the growing need for more sophisticated energy profiling by developing advanced meter functions that far exceed the capability of standard utility meters. Used in conjunction with automatic meter reading (AMR) software, submetering systems provide accurate and timely historical snapshots of a facility's energy use-from a single circuit or device to an entire building and beyond. Especially useful in supporting energy management initiatives, submeter-based AMR systems can combine all of the facility's utility service data, including electric, gas, water and steam, into a single location to show-through a variety of communications options-how, when and where a facility is using energy.
Local area networks in campus environments and multi-facility commercial, industrial and residential sites create new energy monitoring opportunities. Using the facility's existing communications backbone eliminates the need for a modem and telephone line back to the central monitoring location and allows a full-featured Ethernet-based distributed submetering network to be installed quickly and inexpensively.
The Internet can be used to track and analyze big picture electrical consumption (kWh) and demand (kW) from a single circuit to multiple sites around the world. The metered data is transmitted to a data accumulator or profiler and sent via modem to an online server operated by an RBC (read, bill and collect) service or other third-party provider that posts the data online to the subscriber's password-protected folder.
The latest wireless AMR systems provide a unique mesh communication network that allows multi-tenant facility managers to evaluate energy data from submeters without costly wiring or cabling. The energy data is gathered at user-defined intervals from submeters and then imported into the AMR software for analysis and reporting.
The wireless gateway-located inside the metered building-stores the interval energy data until downloaded via Ethernet or Internet to the software.
Together, the wireless software and metering system provide the tools that allow users to:
- Monitor individual single-phase loads including tenants, departments and common areas
- Generate utility bills for tenants or departments based on actual energy usage
- Create load profiles and chart energy usage
Many commercial and industrial customers do not have the resources to manage a full-scale load management system. The latest electronic submeters provide this capability via selectable high and low set points. The high set point allows users to shave electrical demand peaks by shedding loads or activating a local generator. The low kW limit allows the load to be returned to a normal operating power as pre-set parameters are met. A programmable timing feature allows delayed activation to eliminate nuisances such as short-term motor starts. other functions are designed to prevent short-time cycling, which could occur in controlling a heating, ventilating and air conditioning compressor.
Submetering Goes Green
Green building simply refers to optimizing building energy, water and material usage. It is about reducing the impact of buildings on health and the environment through better design, construction, operations and maintenance throughout the building's life cycle.
The first facility environmental rating system was developed in the U.K. by Building Research Establishment Ltd in 1990. Known as the BRE Environmental Assessment Method, this rating system inspired several spin-offs, including the U.S. Green Building Council's Leadership in Energy & Environmental Design rating system and the Green Building Initiative's Green Globes rating system. Although the GBI system is gaining traction primarily due to ease of use and lower cost, the LEED rating system is still the most widely accepted green building benchmarking standard in the U.S. at this time.
Submeter manufacturers have responded to the green challenge by developing next generation hardware and software tools that specifically address the needs of the sustainability market. Offering utility-grade metering accuracy, the latest submeters provide a cost effective way to benchmark and monitor energy usage trends. They measure and verify the ongoing effectiveness of LEED, EPACT, Renewable Energy, Demand Response and other major energy-related initiatives that can positively impact the facility bottom line. Certified to ANSI C12.1 & C12.16 national accuracy standards, new generation green meters offer a number of important features for new construction or retrofit applications, including:
- Scrolling LCD display of kilowatt hour (kWh) usage
- kWh in dollars
- Current demand load (kW)
- Cost per hour, based on current load
- Estimated CO2 emissions in pounds, based on DoE standards
- Estimated hourly CO2 emissions based on current load
- Net metering, including utility-delivered vs. user-received power and net usage
How Submeters Facilitate Green Buildings
Recent industry studies show that green building construction will be a major corporate trend within the next three years. Submeters can contribute directly to the certification of facilities under major energy initiative guidelines including the Energy Policy Act of 2005 (EPACT) and LEED. Specific compliance areas include:
Although introduced nearly 25 years ago, submeters continue to grow in functionality and usefulness, providing great value to facility owners and operators as front line energy data gathering tools in an era of rising utility costs and tightening budgets.
Today's green submeters are even coming out of the electrical room and into the factory floor and building lobbies to give users, tenants, employees and others visibility on actual energy usage and its impact in terms of CO2 emissions, kWh dollars and other parameters that can be easily understood by layman. Submeters not only improve a facility's bottom line, but ease compliance with major energy initiatives while also encouraging every level of the enterprise to become a stakeholder in the energy management and conservation process.
To download a copy of this article click here.