Submeters Help Measure Energy Used By Specific Building Area
SUBMETERS. Given the limitations of working from a utility bill that covers an entire facility, it's not surprising that many energy experts support the use of submeters to measure the energy used by a specific building area — say, the kitchen — or equipment, such as the lighting system. "I see a lot of value in doing submeters," Sinopoli says. "Submeters allow you to really get down to a granular level."
Submeters are a missed opportunity for many facilities. A recent survey of facility managers by Building Operating Management reveals that only about one-third use submeters widely, while another third don't use submeters at all.
When designing or constructing new buildings, submeters are relatively easy and inexpensive to incorporate, Newman says. But it's more expensive to add submeters once a building is complete.
At a minimum, a building should have three meters for its electric load: one to measure the lighting system, another for plug loads and a third for the HVAC system, Newman recommends. If the facility contains a kitchen or laundry facilities, it may make sense to meter those separately as well. In very large buildings, it can be useful to install submeters on the cooling towers and chillers, Newman adds. Then, if the energy consumption reports show a spike in use, the facility manager can further examine the data, checking whether the uptick is due to a change in weather or a result of equipment running after it should have been turned off.
It's critical that all meters and submeters be properly calibrated, Lewis says. That is, they need to be regularly compared to a standard so that it's clear whether the meter readings themselves are accurate. "If you don't calibrate the sensors, the data becomes inaccurate," Lewis says. "Then you're doing a disservice to all the work you did to track all the data."