Introduction
Your home and the office building down the street both run on electricity from the same utility, but they don’t typically use it in the same way at the same time. When a homeowner calls about dimming lights, or a factory reports equipment tripping for no apparent reason, the cause isn’t always inside the building. Sometimes it comes down to the mix of customers sharing the same electrical circuit — who they are, what they’re running, and when they’re running it. That mix is called load diversity, and it has a direct effect on whether the power reaching your wall outlet is clean and steady or plagued by flickering lights and equipment problems.
What is a Load?
A load is anything that consumes electricity — a light bulb, an air conditioner, a factory motor. Every device plugged into the grid draws current (the flow of electricity through a wire), and the sum of all those devices determines the total load on the circuit.
Not all loads behave the same. Some draw current smoothly — a space heater pulls current in a clean, predictable wave. Others, particularly devices with internal electronics like LED bulbs, computer power supplies, and variable-frequency drives (VFDs, which are used to control motor speed), draw current in choppy, irregular patterns. This distinction matters when we talk about harmonics.
Load Diversity
In the simplest terms, load diversity describes the fact that different customers draw power in different amounts, at different times, and with different electrical characteristics. A neighborhood of homes and a strip mall might share the same utility feeder — the circuit that delivers power from the substation — but their electrical behavior is very different.
That variety is generally a good thing. When customers don’t all demand peak power at the same moment, the utility can serve more customers without overwhelming its infrastructure. But when diversity decreases — when too many customers peak at once, or when a circuit is dominated by one type of load — power quality suffers for everyone on that circuit.
Residential vs. Commercial Load Patterns
A typical residential neighborhood is quiet overnight, sees a morning bump as people run showers and coffee makers, dips during the workday, then climbs steeply in the evening as families return home and air conditioning, cooking, and screens all run at once.
Commercial facilities follow nearly the opposite pattern — ramping up in the morning and sustaining heavy usage through the business day as lighting, HVAC, elevators, and computers all run simultaneously, then dropping off sharply in the evening.
Figure 1 shows how residential demand peaks in the evening while commercial demand peaks midday. When they share a feeder, their peaks naturally stagger.
Peak Coincidence
Every customer has a peak demand, but those peaks rarely all happen simultaneously. As Figure 1 shows, residential and commercial peaks land at different times. This staggering means the combined peak on a shared feeder is much lower than what you’d get if everyone peaked at once.
Figure 2 shows how staggered peaks (left) keep combined demand moderate. Overlapping peaks (right) create a much higher combined spike.
When peaks do overlap — a coincident peak — the system is stressed. This can be driven by extreme weather (a scorching afternoon pushes both commercial cooling and residential air conditioning into the same window), or simply by a lack of diversity on the circuit. Coincident peaks are where power quality problems begin.
Impact on Voltage
Every wire in the electrical system loses some voltage along the way — this is called voltage drop, and the more current flowing, the greater the drop.
During a coincident peak, high current increases voltage drop along the feeder. Customers at the far end of the line see their voltage sag. Lights dim. Motors slow down and draw even more current to compensate, worsening the problem.
Figure 3 shows how, under light load (green), voltage stays within the acceptable ANSI C84.1 range (+/- 5% of nominal). Under heavy coincident load (red), end-of-line voltage drops below the limit.
The flip side is also true — during very low demand, minimal current flow means minimal voltage drop, and voltage can creep above its intended level. Utilities manage this balancing act with specialized equipment designed to keep voltage steady, but that equipment is tuned for expected patterns. When coincident peaks exceed what was planned for, the system’s ability to hold voltage within acceptable limits is tested.
Impact on Harmonics
The power system delivers electricity as a smooth wave cycling 60 times per second — known as 60 Hz (50 Hz in some parts of the world). Harmonics are distortions that ride on top of that wave at whole-number multiples of the base frequency — 2x, 3x, 4x, and so on — warping its shape.
Figure 4 shows a clean 60 Hz waveform (left) versus one distorted by harmonics (right). The flat-topped, rippled shape is a telltale sign of harmonic distortion. This was captured using a Power Monitors recorder and taken from the PQ Canvass cloud application, which has a very robust suite of tools for analyzing waveform captures.
Any device that draws current in a non-smooth way — a nonlinear load like an LED bulb, computer power supply, or VFD — injects harmonics into the system. Individually, each contributes a small amount, but they add up.
Load diversity plays an interesting role here. Different types of nonlinear loads produce different harmonic patterns. When those different loads share a feeder, their harmonics can partially cancel each other — a hidden benefit of a diverse load mix. When diversity is low, similar loads produce similar harmonics that stack up instead of offsetting. The result is elevated total harmonic distortion (THD), which can overheat transformers, trip breakers, and shorten equipment life.
Applicability to a Power Quality Investigation
For anyone investigating a power quality complaint, understanding load diversity on the circuit is a critical first step. The key questions are straightforward:
- Is the circuit diverse or uniform? A mix of customer types benefits from natural diversity. A single type does not.
- Are coincident peaks driving voltage issues? If complaints cluster during specific times or weather conditions, coincident peaking may be the culprit.
- Are harmonics accumulating? If THD is elevated, a lack of diversity — and the cancellation it provides — could be a contributing factor.
Knowing the answers changes what you do next. If you understand the load mix, you know when to focus your monitoring — a residential evening peak is a very different analysis window than a commercial midday plateau. A voltage complaint on a feeder full of similar customers points toward coincident peaking, while elevated THD on a low-diversity circuit suggests harmonic stacking. And when it comes time to recommend corrective action, understanding diversity helps distinguish between “the system is undersized” and “the load mix has shifted” — two problems that lead to very different solutions.
Recognizing these patterns transforms raw monitoring data from a wall of numbers into a coherent story.
Conclusion
Load diversity is a measurable characteristic of every electrical circuit. It influences whether voltage stays within limits, whether harmonic distortion remains manageable, and whether power is clean enough to keep equipment running. Knowing how to recognize shifts in diversity is what turns a power quality investigation from guesswork into diagnosis.
