Demand-Side Management: Reducing Chiller Load Through Building OptimizationThe most efficient chiller is one that doesn’t need to run—or runs at reduced load. Demand-side management (DSM) strategies reduce the cooling load delivered to the chiller plant, directly proportionally reducing chiller energy consumption. Building-side optimization should always precede chiller-side optimization.Envelope and Internal Load ReductionBuilding envelope improvements—better insulation, high-performance glazing, external shading devices, and cool roofs—reduce the solar and conductive heat gain that chiller systems must overcome. Interior load reductions through LED lighting (which generates far less heat than fluorescent or incandescent), efficient plug loads, and occupancy-based control can reduce cooling loads by 10–30% in older buildings.Economizer Hours and Natural VentilationAir-side economizers bring in outdoor air for free cooling when ambient conditions allow. ASHRAE 90.1 mandates economizers in many climate zones, but proper operation and maintenance are critical. Economizers that are disabled, stuck closed, or poorly controlled eliminate this free cooling opportunity. BMS data analysis can quantify actual economizer hours versus potential hours, identifying control or mechanical problems.Thermal Energy StorageIce or chilled water thermal energy storage (TES) systems shift chiller operation from expensive on-peak hours to cheaper off-peak nighttime hours. The chiller charges the storage medium overnight, and stored cooling is discharged during peak daytime demand. Beyond utility bill savings, TES can reduce peak chiller plant size by 30–50%, and in some cases, nighttime operation benefits from cooler outdoor temperatures that improve condenser efficiency.Zone Temperature Setpoints and SchedulingRaising cooling setpoints by even 1°C during occupied hours can reduce chiller load by 3–5%. Extending setback periods—maintaining higher temperatures when spaces are unoccupied—provides compounding savings. Occupancy sensors, smart thermostats, and demand-controlled ventilation all contribute to reducing the cooling load that the chiller must satisfy. These measures should always be coordinated with occupant comfort requirements.Pro Tip: For every dollar invested in reducing building cooling loads, you save the equivalent of $3–5 in chiller plant capital and operating costs over the equipment lifecycle.