Automation.com eNewsletter June 2011
Submetering Solutions for Building
Management Systems (BMS)
A key element of today’s sustainable building management system, submeters acquire
and transmit a variety of energy data parameters for analysis and reporting through
the BMS for common area cost allocation, fair and accurate tenant billing, power
factor penalty identification, utility meter shadowing and other energy-saving capabilities of tangible value to the facility’s operational bottom line.
By Don Millstein
E-Mon (http://www.emon.com/auto611a.asp)
Scraping the sky at 975 feet above ground, the tallest building on the Philadelphia skyline is also the
loftiest “green building” in the United States. Completed in June 2008, the 58-story skyscraper’s
1.25 million-square-foot, state-of-the-art structure received a Gold rating under the U.S. Green
Building Council’s LEED-CS (Core & Shell) category in April 2009.
The sustainable design philosophy guiding the construction of the building resulted in 40 percent less water use than
typical office buildings and a 70 percent lower heat-island effect from the pavement. Equally important to the
developer’s sustainable design goal was the implementation of an energy-efficient building management system
(BMS) to optimize comfort and facilitate productivity for the building’s more than 3,000 occupants.
In operation, the BMS provides a state-of-the-art control system that coordinates all of the climate, lighting, energy
consumption and scheduling systems through a single integrated, Internet-based source. The building’s intelligent
infrastructure compiles large amounts of data and sends it via the Internet to a central monitoring and control location
for daily operations management. The BMS calculates the exact cost of producing BTUs for heating, cooling and
steam, including the electrical cost for pumps and steam for driving the air-conditioning system. Chilled water, gas
and other measurements are also factored into the mix.
Submetering system extends performance of skyscraper’s BMS
Operating in parallel to the BMS, a facility-wide network of E-Mon D-Mon electric submeters accepts energy data
from the BMS and imports it into E-Mon Energy software. This PC-based energy intelligence software analyzes and
converts the raw meter data into monthly utility billing statements for the building’s tenants. Shown in Figure 1,
elements of the system include some 205 Class 3000 E-Mon D-Mons, 91 BTU meters, seven steam meters, 17 water
meters, eight gas meters and 58 airflow meters. This does not include utility meters, of which two steam, and one each
gas and water meter are also part of the system. The airflow meter data is also imported into E-Mon Energy software
from the BMS.
Figure 1: Block diagram showing the parallel operation of the facility’s BMS and the submetering
system used for utility metering and tenant billing via a single hardware / software platform.
The submetering system not only accurately meters the electrical, but meets the user’s complex billing requirements
of incorporating gas, water, steam and BTU metering into a single hardware/software platform. Coincidental demand
billing, in which the peak demand (kW) of the entire building, not just the individual tenant, is also factored into the
mix, along with the ability to identify tenants that cause a power factor penalty to the building. Because this facility
buys high-voltage electricity in bulk rates and transforms it down, the power is less expensive than electricity
purchased at 480 or 208V levels. Consequently, that cost savings is passed through directly to the tenants.
The billing software factors not only electrical into the mix but also allocates costs to those tenants using water,
steam, gas and other utilities. The facility’s sophisticated “coincidental demand” structure views tenant energy consumption patterns from a number of different angles, including:
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Comparison of present to previous month;
Comparison of year to date with previous year;
Watts per square foot;
Ratchet charge billing;
Power factor corrected billing;
Percentage of highest load.
Figure 2. Submeters acquire the energy data using 0-2V output split-core current
sensors that are installed non-invasively around the electrical feeds being metered.
This eliminates having to power down the load and makes for a safer, faster install
for the electrical contractor.
How submeters facilitate BMS performance
The level of profiling needed by high-volume energy consumers is simply unobtainable using the
standard utility meter found at the main electrical service entrance. That’s why growing numbers of
facilities like the aforementioned Philadelphia skyscraper are using submeters to help identify opportunities to save literally thousands of dollars in reduced energy costs through:
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Usage analysis and peak demand identification;
Time-of-use metering of electricity, gas, water, steam, BTUs and other energy sources;
Cost allocation for tenant billing;
Measurement, verification and benchmarking for energy initiatives, including LEED Energy & Atmosphere
(EA) and Water Efficiency (WE) credits;
 Load comparisons;
 Threshold alarming and notification;
 Multi-site load aggregation and real-time historical monitoring of energy consumption patterns for negotiating
lower energy rates, and more.
SUBMETER TYPE
SPECIFICATIONS
Socket Type
Electromechanical/Solid State
Electronic
Non-socket Type
Feed-thru Type
Current Xfmr Type
$1,000
Not Applicable
$16,000
2–3 Hours
2–3 Hours
320 Amp, Max.
2 Square Ft
Utility Room
Not Applicable
$2000 - $5000
Not Applicable
6–8 Hours
6–8 Hours
None
11.7 Square Ft
Utility Room
$700
$800
$5,500
1 Hour
None
None
0.25 Square Ft
Anywhere
Yes
18.1 Square Ft
Optional/Yes
No/Yes
No
No
No
No
No
Yes
18.1 Square Ft
Optional/Yes
No/Yes
No
No
No
w/ CT Change
No
Yes
2 Square Ft
Standard
Standard
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
Available
Yes
No
Yes
Yes
Yes
Yes
No
Available
Yes
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
INSTALLATION
Installed Cost (estimated)
Stand alone, up to 320A, 3Ø
Stand alone, over 320A, 3Ø
8-Meter Unit, 200A, 3Ø
Installation Time
Power Interruption
Amperage Limitations
Space Requirements
Installation Location
FEATURES
Multiple Meter Units (MMU)
Size of 8-Unit Cabinet
Digital Readouts
Reset Capabilities
Multiple Load Monitoring
Subtractive Load Monitoring
Monitor Specific In-Panel Circuits
Amperage Modification in Field
Meter UL listed
ENHANCEMENTS
Digital-to-Analog Profiles
Pulse Outputs
Timed Metering
Software Monitoring
Upgradeable in the Field
Power Quality Functions
Net-Metering Capability
Form C Control Relay Output
Source: E-Mon
Table 1. Whether designed in or retrofitted, submeters are installed on the “building side” of the
main utility meter to measure energy usage from the enterprise level all the way down to a
single device or circuit panel. Sold through distribution, electric submeters are easily integrated
with water, gas and other pulse-output utility meters, and energy intelligence software, to
provide a total facility energy snapshot. Non-socket-type electronic submeters are less
expensive initially, quicker and easier to install and offer superior performance and options
compared to other types.
Of the three main submeter types shown in Table 1, the first two—feed-through and current transformer (CT)-based (Figure 2)—are socket-type meters. CT-style socket meters are used with loads
of 400A and above. In commercial applications, they may be specified but will take up a lot of
space in the electrical room due to the need for CT cabinets and the meter bases. The extra space requirement cuts into
the available rental space, which is undesirable in the commercial marketplace. Another major disadvantage in many
jurisdictions—socket meters are not UL listed. The third type is the electronic submeter, a non-socket device that provides clear advantages over the previous two.
Since their introduction in the 1980s, submeters have grown dramatically 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 submeters are coming out of the electrical room onto the factory floor and into 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 easily understood by laymen. Submeters not only improve the facility
bottom line, but facilitate implementation of building retro-commissioning projects and other energy initiatives while
also encouraging every level of the enterprise to become a stakeholder in the energy management and conservation
process. A new generation of advanced submeters (Figure 3) offers a number of important functions and capabilities
for new construction or retrofit applications, including:
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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;
Compatibility with pulse-output utility meters, including water, gas, BTU, steam, etc.
Figure 3. In response to EPAct 2005, EISA 2007 and other federal energy guidelines
dotting the facility landscape, E-Mon and other manufacturers have developed advanced
hardware and software tools that specifically address the needs of the sustainability market.
Certified to ANSI C12.1 & C12.16 national accuracy standards, new-generation advanced
meters like E-Mon’s Green Class meter (shown here) offer a number of important functions
and capabilities for new construction or retrofit applications.
Figure 4. Internet-based meter dashboards like E-Mon’s Web-Mon allow users to automatically
integrate their distributed metering infrastructure into real-time meter dashboards via openarchitecture Modbus IP-compatible LAN/WANs. Dashboards are available for single-facility as
well as multi-facility campus-type applications to provide real-time and historical presentment of
electricity, gas, water, steam, BTU and other metered parameters.
Meter dashboards for BMS energy data presentment
Where high-volume energy consumers pay for both consumption and peak demand, potentially greater savings may
be realized, especially where high demand is created for short periods of time—as, for example, as the result of
inefficient air conditioning or some energy-intensive device or process occurring during peak periods. If tariff rates
for consumption vary based on time-of-day or season, and peak demand charges are high, on-going potential benefits
may become significant. If power is being purchased under a real-time pricing tariff or contract, even greater benefits
may result.
By importing data from electric submeters and other metering devices into Web-based communications (Figure 4),
interval data may be cost-effectively collected, analyzed and displayed in near real-time to allow facility managers to
shed load and perform other peak-shaving actions to lower their demand charges. Meter dashboards often include:
 Automobile-style gauges showing how power, fuel, energy budgets are being consumed on a real-time basis;
 24-hour load profiles for power, chilled water, steam or other building systems;
 Historical comparisons of current usage versus previous time periods under similar conditions (time, day of
week, temperature) (Figure 5);
 Automated carbon foot-print calculations;
 Tenant- or consumer-level information about energy use and efficiency efforts.
Bottom line considerations
There is no question that green building construction will continue to be a major trend across the
facility landscape. An enabling technology, submeters can help facilities improve their bottom lines
by benchmarking, measuring and verifying compliance with major energy initiative guidelines,
while also encouraging every level of the enterprise to become a stakeholder in the energy
management and conservation process. The Philadelphia skyscraper highlighted at the beginning of
Figure 5. Meter dashboards are a great way to visualize what your electrons are doing on a 24/7
basis to impact your facility’s operational profile. Shown here, are comparative demand graphs
for the metered lighting and HVAC panels over a three-day period, monitored in time intervals of
15, 30 or 60 minutes.
this paper is a textbook example of how submeter networks are helping state-of-the-art facilities support sustainability
and improve energy efficiency, while optimizing tenant satisfaction and providing a very high degree of granularity in
terms of visibility of the facility’s total energy profile.
In addition to the direct benefits of improving operational efficiency through implementation of green practices, some
states are beginning to offer tax credits for both new and renovation projects that incorporate sustainable building
practices based on LEED certification levels. As today’s facility operators face ever-tightening operational challenges,
new technologies and strategies will be needed to keep pace with rising costs while, at the same time, maintaining or
improving service quality levels.
One such energy strategy, performance-based contracting, can result in major cost savings with little or no up-front
investment. Utilizing project-related savings to underwrite energy improvements on a pay-as-yougo basis, submetering technology can be used to identify inefficiently operating equipment,
allowing repair or replacement. The cost savings realized from reducing operational inefficiencies
can then be applied to other areas, including deferred maintenance or installing other energy-saving
equipment or services.
For further information about E-Mon’s complete line of hardware and software solutions for automatic meter reading
applications, visit www.emon.com/auto611a.asp or call 1-800-334-3666 today!
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About the author
Don Millstein is President and CEO of E-Mon of Langhorne, PA. As a veteran energy industry speaker and author,
Don is a former participant in utility deregulation in California, New Jersey, New York and Pennsylvania. He is a
member of the DOE’s FEMP task force, Alliance to Save Energy, the U.S. Green Building Council and other energy
conservation-related organizations. He may be contacted at dmillstein@emon.com.