Profile Energy Use Patterns
Profile Energy Use Patterns
Understanding Your Facility’s Electrical Demand Profile
Introduction, Profile Energy Use Patterns
Considerable information about your facility’s operations can be revealed by its electrical demand profile. This time record of energy consumption shows which electrical loads are operating at any given moment and the aggregate demand those loads collectively represent. Beyond simple monitoring, the demand profile can expose loads that are running unnecessarily and identify systems that are inappropriately sized for their actual workload.
Because the cost of electricity is determined in part by the maximum demand drawn during a billing period, reducing that peak demand can significantly lower your energy costs. Depending on the size of your facility and available resources, it may even be possible to install temporary sub-metering at various locations to build a more granular picture of your consumption.
Your electrical utility may also be able to provide a demand profile or assist you in obtaining one. Although the demand profile specifically measures electrical energy, it simultaneously provides insight into the consumption of other forms of energy. Think of it as an operational fingerprint — a unique energy signature of your entire facility and a cornerstone of any thorough energy audit.
💡 Key Insight: The demand profile is your facility’s electrical fingerprint. It is one of the most powerful diagnostic tools available to an energy auditor, revealing both waste and opportunity in a single visual record.
What Is a Demand Profile?
The demand profile for a facility, building, service entrance, or any electricity user is simply a record of power demand (rate of energy use) over time. Its purpose is to provide detailed information about how the facility as a whole uses energy. As the electrical fingerprint of the facility, it is extremely useful for ongoing energy tracking and comparison.
The simplest form is a series of manual utility meter readings — recorded monthly, daily, hourly, or more frequently — and the appropriate interval depends on how the data will be used. The most informative profiles, however, are generated by a recording power meter, which captures readings automatically at intervals of less than one minute, revealing far more detail than hourly manual readings ever could.
A standard 24-hour demand profile plots power demand (in kW or kVA) on the vertical axis against time on the horizontal axis. More sophisticated recording meters can also capture three-phase voltage, current, and power quality parameters simultaneously.
Table — Events to Look For in a Demand Profile
| Information | Description |
|---|---|
| Peak Demand | The time, magnitude, and duration of the peak demand period or periods may be determined. |
| Night Load | The demand at night or during unoccupied hours is clearly identified. |
| Start-up | The effect of operational start-ups upon demand and peak demand may be determined. |
| Shutdown | The amount of load turned off at shutdown can be identified and should equal the start-up increment. |
| Weather Effects | The effect of weather conditions on electricity demand can be tracked from day to night and season to season. |
| Loads That Cycle | The duty cycle of many loads is usually visible and can be compared to expected behaviour. |
| Interactions | System interactions may be evident — e.g. increased demand for electric heat when ventilation dampers open. |
| Occupancy Effects | Occupancy schedules are often reflected in the profile; if not, it may indicate control problems. |
| Problem Areas | A short-cycling compressor, for example, is usually easy to spot from the demand profile. |
Obtaining a Demand Profile
Facility demand profiles can be obtained by several methods, ranging from simple manual readings to sophisticated dedicated monitoring systems. The right choice depends on your budget, technical capacity, and the depth of information required.
📋 Periodic Utility Readings
Cheapest and simplest. No capital cost; readings match utility data exactly, though time resolution is limited to hourly intervals.
🔌 Recording Ammeter
Measures current draw over time. Useful but assumes constant voltage and power factor — verify before relying on results.
⚡ Recording Power Meter
Measures kW, kVA, KWH and power factor simultaneously. The most commonly used method for accurate profiling.
🏢 Energy Management System
Measurements are ongoing and routine. Often already capable but may lack watt sensors. Ideal for continuous monitoring.
🖥️ Dedicated Monitoring System
Highest accuracy and data storage. Core of integrated monitoring solutions; provides sub-meter information for facility sections.
Whatever technique is used, it is important to measure the demand profile during a period when facility operations are typical — and ideally when peak demand equals the peak registered on the utility meter for the current billing period. The overall objective is to identify which loads are actually contributing to the billed peak demand.
Analysing the Demand Profile
Analysing a demand profile is equal parts science and art. Technical knowledge provides the framework, but interpretive skill — developed through practice and good familiarity with the facility — is equally essential. The goal is to pinpoint loads that operate unnecessarily, those that inflate peak demand, and those that indicate a maintenance issue.
Many electrical loads leave very distinct patterns as they operate. By learning to recognise those patterns, an auditor can attribute different portions of the demand curve to specific equipment or systems. The recommended approach follows four steps:
- Compile a load inventory. Begin with a complete list of electrical loads in the facility . This inventory gives context to every feature you see in the profile.
- Mark significant occurrences. Identify abrupt demand changes, the top three peak demands, repeated patterns, flat sections, dips during peak periods, and the minimum demand level.
- Map operational events to the time axis. Note when start-up, shutdown, coffee breaks, lunch, shift changes, and other notable events occur. This helps correlate demand features with actual work patterns.
- Use analysis tools and examples. A spreadsheet template — such as the Profile.xls tool included in the audit guide — allows you to graph data and generate a load duration curve, showing how long the demand exceeds any given threshold. This considerably simplifies demand-control opportunity assessments.
Opportunities for Savings
Once you can read a demand profile fluently, savings opportunities often reveal themselves clearly. The following are among the most typical:
- A brief, sharp peak well above the rest of the profile is an opportunity to reduce demand through load scheduling.
- A high night load in a facility with no night operations signals potential savings through better automatic or timed controls.
- Loads that cycle on and off during unoccupied periods may be shut down completely rather than allowed to continue cycling.
- Insignificant demand drops during production breaks suggest idling equipment — consider full shutdowns during those intervals.
- Early system start-ups before occupancy and late shutdowns after operations end waste energy that even half-hour adjustments can recover.
- Peak demand at start-up is a classic sign that staged start-up sequencing could reduce the peak.
- A billed demand peak that never appears on typical daily profiles suggests a rare but impactful load — schedule or shed it.
- Short-cycling loads point to both energy waste and accelerated equipment wear — a maintenance and efficiency opportunity simultaneously.
Savings Through Power Factor Correction
Power factor is the ratio of real power (kW) to apparent power (kVA). For customers billed on kVA demand, improving power factor directly reduces the billed peak demand without reducing actual work output. Correction strategies include installing fixed or variable capacitor banks at the service entrance, at major switching points in the distribution system, or at individual motor terminals. For very large systems, an over-excited synchronous motor can serve the same function as a large capacitor bank.
Other Useful Profiles
While electrical demand profiling is the centrepiece of this chapter, many other parameters can and should be profiled during an audit using dedicated data loggers. These compact devices can track temperature, occupancy, humidity, light levels, and more — often generating immediate energy management opportunities (EMOs) through the patterns they reveal.
A compelling example is the combination of occupancy and light-sensor logger. In one documented case, this device revealed that lights remained on when an area was vacant for 24% of the time — a clear, low-cost case for motion-sensor lighting installation. Such findings are typical of what broader profiling can uncover and underline why demand profiling should extend beyond electricity to encompass every energy-consuming system in the facility.
Key Takeaways
- The demand profile is the electrical fingerprint of your facility and the foundation of any serious energy audit.
- Multiple profiling methods exist — choose based on your budget, accuracy requirements, and the depth of insight needed.
- Analysing the profile is both technical and interpretive — correlate demand features with operational events.
- Savings opportunities are often visible directly in the profile: night loads, short cycling, demand peaks, and idling equipment.
- Power factor correction can reduce billed kVA demand without affecting real power output.
- Extend profiling beyond electricity to lighting, occupancy, and other parameters to find additional EMOs.
Source: Energy Audit Manual & Tool · Natural Resources Canada
