If you are noticing long equipment run times, higher energy bills, or heating and cooling running at the same time, the problem may not be your HVAC equipment. In many commercial buildings, the real issue is how the system is being controlled. Small control problems often go unnoticed, but over time they waste energy and shorten equipment life.
In commercial buildings, HVAC systems are designed to respond to changing conditions. When controls are not set up correctly, systems can run longer or harder than needed. This leads to higher utility costs, more wear on equipment, and more comfort complaints.
At Harold Brothers Mechanical Contractors, we specialize in finding and fixing energy waste caused by control strategies, not mechanical failures. We have helped many building owners lower energy costs and extend equipment life by adjusting how systems are programmed and operated.
In this article, we explain four proven energy reduction strategies that can be used with most existing commercial HVAC systems: variable frequency drives (VFDs), setpoint resets, scheduling, and demand limiting. You will learn how each strategy works, when it makes sense to use it, and what problems can occur if it is not applied correctly.
Energy reduction strategies are control-based methods used to lower HVAC energy use without hurting comfort or reliability. Instead of replacing equipment, these strategies focus on how systems react to real building conditions.
Most modern commercial HVAC systems already have the hardware needed to support these strategies. What is often missing is proper setup, fine-tuning, or regular review of how the system operates day to day. When controls are left unchecked, energy-saving features may exist but provide little real benefit.
HVAC systems use energy based on how often they run, how hard they work, and when they are allowed to operate. Poor control strategies can cause systems to run when they do not need to or work harder than necessary.
Common signs of control-related energy waste include fans running at full speed during low occupancy, heating and cooling running at the same time, equipment operating overnight or on weekends, and high peak demand charges that are hard to explain.
In many cases, fixing these issues starts with reviewing control logic, not replacing equipment.
A variable frequency drive allows a motor to change speed instead of running at full speed all the time. In HVAC systems, VFDs are often used on fans, pumps, and compressors.
Instead of cycling on and off, the motor speeds up or slows down to match the building’s actual demand. This helps reduce wasted energy during low-load conditions.
VFDs can greatly reduce energy use because motors consume much less power at lower speeds. They also reduce wear on belts, bearings, and other parts, which can extend equipment life and lower maintenance costs.
VFDs only save energy when they are controlled correctly. If setpoints are too tight or schedules are wrong, the motor may still run near full speed most of the day.
VFDs work best in buildings with changing occupancy, long run hours, or systems where airflow or water flow changes often.
Setpoint resets adjust temperature, pressure, or airflow targets based on current conditions. Instead of holding one fixed value all day, the system relaxes setpoints when demand is lower.
For example, during mild weather, a system may allow slightly warmer supply air, reducing cooling energy while keeping spaces comfortable.
Setpoint resets reduce unnecessary work by the HVAC system. They help prevent overcooling or overheating, which often leads to reheating and wasted energy.
If resets are too aggressive or not coordinated with other controls, comfort problems can occur. Reset strategies must match how the building is actually used.
Setpoint resets are common in office buildings, schools, and facilities with predictable changes in load throughout the day.
Scheduling controls when HVAC systems are allowed to operate. Proper schedules make sure equipment runs only when spaces are occupied or needed.
This includes start times, stop times, holidays, and seasonal changes. Good scheduling prevents systems from running during unoccupied hours.
Scheduling is one of the simplest and lowest-cost energy reduction strategies. When done correctly, it can deliver immediate savings.
Schedules often drift over time. Temporary overrides, staff changes, or changes in building use can leave systems running much longer than intended.
Scheduling is essential for almost all commercial buildings, especially those with regular operating hours or centralized controls.
Demand limiting controls how much electrical load a building can draw during peak periods. When demand approaches a set limit, non-critical loads are reduced or staged off.
This helps control utility demand charges, which can make up a large portion of a commercial energy bill.
Demand limiting helps manage peak energy costs without shutting systems down completely. It allows energy use to stay more predictable.
Demand limiting requires careful planning. If priorities are not set correctly, it can affect comfort or important building operations.
Demand limiting works best in large commercial buildings, facilities with demand-based utility rates, and buildings with a well-configured BMS.
|
Strategy |
What It Controls |
Strengths |
Limitations |
Best Fit |
|
VFDs |
Motor speed |
Large energy savings |
Needs proper control logic |
Variable-load systems |
|
Setpoint Resets |
Temperatures, pressures |
Reduces over-conditioning |
Needs tuning |
Predictable load changes |
|
Scheduling |
Run times |
Simple and low cost |
Can drift over time |
All commercial buildings |
|
Demand Limiting |
Electrical demand |
Controls peak charges |
More complex setup |
Large facilities |
Many energy problems are caused by control issues rather than failing equipment. These include setpoints that were never updated after occupancy changes, schedules that were overridden and forgotten, VFDs locked at fixed speeds, and demand limits disabled to avoid complaints.
When this happens, energy use rises even though the system appears to be working normally.
At a mid-size office building in Fall River, energy bills increased despite no equipment failures. Fans had VFDs, but fixed pressure setpoints kept them running near full speed all day. After adjusting control logic and improving scheduling, energy use dropped and comfort complaints decreased without replacing any equipment.
Energy reduction strategies depend heavily on the building automation system. Sensors, schedules, priorities, and control logic all determine how well these strategies work together.
When controls fall out of alignment, energy-saving features may exist on paper but deliver little real value in practice.
Reducing HVAC energy use does not always mean replacing equipment. In many cases, better control makes the biggest difference. Now that you understand how VFDs, setpoint resets, scheduling, and demand limiting work, you can start identifying where your building may be wasting energy.
The root problem is often hidden in control logic. Fan speeds that do not adjust, schedules that were changed months ago, or disabled demand limits all contribute to higher energy costs.
If you want to take the next step, we recommend reading our article on Commercial BMS & Controls Optimization for Comfort and Efficiency. It shows how these strategies work together across your entire system.
The team at Harold Brothers works with building owners and facility teams to find control issues, lower energy costs, and improve comfort without unnecessary equipment replacements.