Simulate a utility demand response event for different building types. Select DR strategies, set the event window, and see the load shape — including pre-cooling, load shed, and rebound peaks — with estimated peak demand reduction and cost savings.
This simulator models the building electrical load profile during a utility demand response event, showing the impact of load shedding strategies, pre-cooling, and rebound peaks on peak demand and energy cost. Engineers and energy managers use it to evaluate DR program participation and estimate monthly demand charge savings.
Demand response (DR) events are utility-issued signals requesting that a building reduce its electrical demand during grid stress periods, typically for 2–4 hours on peak summer afternoons. The simulator models three strategies: thermostat setpoint float (raise cooling setpoint by 2°F, reducing HVAC load ~10% during the event but requiring 8% pre-cooling load increase for 2 hours beforehand to pre-charge the building thermal mass), lighting dimming (reduce non-critical lighting by 10%, reducing load ~4% with no rebound), and plug load shedding (shut off non-essential equipment, reducing load ~6% with minor 2% rebound).
Rebound peaks occur 1–2 hours after the event ends when deferred cooling and plug loads resume simultaneously. The simulator accounts for pre-cooling load increase, event load reduction, and rebound load increase for each strategy.
OpenADR 2.0 (Open Automated Demand Response) is the primary protocol for automated DR signaling in commercial buildings, standardized as CTA-2045 and IEC 62746-10-3. The protocol carries DR event signals from the utility or aggregator to the building automation system, which executes the DR response sequence automatically. ASHRAE Guideline 36 includes DR mode sequences for HVAC systems. Most US utility DR programs offer two pricing structures: capacity programs (payment for committing to curtail) and event-based programs (payment per kWh or kW reduced during called events).
Pre-cooling effectiveness depends on the building's thermal mass: heavyweight concrete construction stores more thermal energy than lightweight steel-stud construction, sustaining comfort longer into the event. The thermostat float strategy becomes uncomfortable if the space temperature drifts above 78–80°F; this limits event duration and magnitude of setpoint raise. DR strategies must be coordinated with the building's base load sequence to avoid conflicts — for example, a chiller minimum flow protection sequence may override DR load shedding commands. Demand charge savings calculations assume the DR-adjusted peak becomes the monthly billing demand; verify with the actual utility tariff, as some tariffs use a 15-minute interval peak rather than an instantaneous demand reading.
Select the building type to load a representative 24-hour load profile, set the DR event start time using the slider or preset buttons, and check the DR strategies to apply. The 24-hour load profile chart shows the baseline (dashed), DR-modified (solid), pre-cooling window (yellow), event window (red), and rebound window (purple). The results cards show baseline peak, actual peak, peak reduction in kW, energy shed in kWh, estimated monthly demand charge savings, and energy cost savings per event.
A demand charge is a utility bill component based on the peak electrical demand (kW) in a billing period, typically measured as the highest 15-minute average demand in the month. By reducing peak demand during a DR event that coincides with the building's monthly peak, the DR-adjusted peak becomes the billing demand, reducing the demand charge for the entire month.
Most utility DR programs require a 10–30 minute advance notice before the event starts. OpenADR 2.0 can deliver signals with minutes of advance notice for fast-response programs. ASHRAE Guideline 36 defines a DR mode that the BAS activates upon receiving the OpenADR signal, executing pre-programmed load shedding sequences without operator intervention.
Pre-cooling cools the building to the lower end of its comfort band (e.g., 70°F) before the DR event, storing thermal energy in the building's structure and contents. During the event, the thermostat setpoint floats upward while the pre-stored cooling maintains acceptable comfort. Pre-cooling increases load before the event but reduces the demand peak during the event, which is what affects the demand charge.
OpenADR 2.0 is an open, interoperable communication protocol for DR signaling between a utility's Virtual Top Node (VTN) and a building's Virtual End Node (VEN) — typically the building automation system or an energy management system. The BAS acts as the VEN, receives DR signals, and automatically executes the DR response sequence per Guideline 36 without requiring manual operator intervention.
Buildings with high demand charges, large thermal mass, flexible HVAC systems, and significant lighting and plug load flexibility benefit most. Office buildings, retail centers, and hotels are well-suited. Data centers and hospitals have limited DR flexibility due to critical loads. Buildings with on-site battery storage can dispatch stored energy during DR events, combining storage and load shedding for maximum demand reduction.
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