RCx and Battery Energy Storage: The Perfect Pairing

With increased incentives and falling battery costs, commercial customers are asking us whether battery energy storage systems (BESS) are right for them. Before we can answer that question, we need to do our homework on your building’s current energy use. That includes considering your current load shape and the potential benefits of improving it through retro-commissioning (RCx). Why do we think it makes sense to link RCx and BESS? Let us explain how RCx can provide the most cost-effective solution.

Determining BESS sizing, cost, and savings is more complex than other distributed energy resources such as photovoltaics. Right sizing a BESS depends more on the shape of the demand profile than the magnitude of peak demand or total energy consumed. When analyzing your building’s historic energy use, we look for trends that allow us to predict its future energy consumption, or more specifically, its daily load shape. If your building hasn’t been properly maintained, its energy use may not be consistent, and its likely to be consuming more energy – costing you more. Since the goal of sizing a BESS is to reduce your peak demand costs, tuning up your building’s operation to reduce your energy spend increases the cost effectiveness of BESS, and may help reduce the size system that you need.

One of the ways we help our customers improve their building’s performance is through the retro-commissioning process. RCx is the operational tuning of a building that saves energy, peak demand, and energy costs in addition to increasing occupant comfort. Once we tune up a building through the RCx process, your building will use less energy, and it will use it more predictably. Your building’s new load profile is what you want to maintain to realize savings over time and what we will use to assess the cost effectiveness of BESS.

Predictive algorithm estimated load profile compared to actual


Monitoring your building’s load profile is the other critical piece that ensures that the tuned operating mode persists. Quite conveniently, the monitoring required to effectively control BESS also proves useful for maintaining the operational performance of a building.

Battery controls on BESS work to anticipate and minimize peak demand by discharging the batteries when its most beneficial. The more predictable the energy consumption of the building is, the better the battery controls can limit peak demand. When consumption follows consistent trends, a lower peak demand threshold can be maintained without oversizing the BESS. Also, fewer battery discharges may be needed, extending the battery useful life. This is why RCx is an excellent precursor to BESS.

BESSs are installed either as standalone installations or sometimes paired with solar. In either case we recommend RCx in advance to better evaluate the potential overall savings. In a future post we will discuss some of the nuances of sizing BESS for your building and opportunities for combining persistence monitoring with BESS controls.


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