Electric utilities provide power at different times of day. During peak-demand times, utilities have to pay more for the power. Power that buildings use at these peak times usually comes from distant sources or from less sustainable generating systems. Some utilities have developed different rate structures to provide incentives or reduced rates to customers that use less power at peak-demand times.
One way to qualify for these utility programs is to install a demand meter. A normal electric meter records the amount of energy used for a particular amount of time, such as the number of kilowatt hours a building uses in a month.
By contrast, a demand meter records the highest amounts of power used at one time, usually a 15-minute period. The demand meter’s goal is to move demand loads from the peak times — usually during the day — to lower demand times, usually at night. This shift can reduce the cost of power the utility must buy and the rates they charge customers during peak-load times, as well as lessen the overall impact on the energy grid.
Demand meters are similar to smart meters. A movement is growing among some utilities to install smart meters in a customer’s facility to monitor energy. The smart meter can monitor times during which the facility is placing high demands on the utility grid. The customer can watch the meter and start taking electricity loads offline during these peak loads.
Some systems automatically monitor peak-load times. In some cases, the meter can cut power to a particular piece of equipment or postpone when large pieces of equipment come on. This strategy could benefit commercial buildings with good databases of electrical loads and a smart meter that monitors the system to control non-critical pieces of equipment.
After sub-meters have been in place, an operator can collect energy data and develop a baseline of energy use for different processes, equipment, and functions in a facility. Comparing this data with demand-meter data can help the operator locate energy loads the facility can remove during peak-load times.
For example, a large food-service company determined ice makers in the kitchen had a peak-load time during the same time operations were at a peak. So with the facility’s air conditioning demands already at their peak, the heat generated by ice makers only added to the peak demand. The facility needed to replace the ice makers and realized they could buy ice makers with larger storage capacity, meaning they could make the ice at night during off-peak energy load and off-kitchen load times.
It is important for managers to understand the costs and resulting workload of installing meters, communications, servers, hardware and programming to support the technology. Water and gas meters cause pressure drops in piping systems. Managers must develop, review, and implement procedures for operating the installed systems, and they have to contact utilities and approve contracts to obtain reduced rates, remembering that rate programs can change while systems operate.
Winston Huff is a project manager, system designer, and sustainable coordinator with Smith Seckman Reid a consulting engineering firm in Nashville, Tenn.
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