Electrical Load Analysis

An electrical load analysis tells you how much of your system’s capacity is in use, where, and how much is left. We build it from a combination of calculated loads (the connected equipment and its demand) and measured loads (metering or a load recording over time), then compare the result with the ratings of your service, transformers, feeders and panels. The study shows whether you can add equipment, whether phases are balanced, and where a circuit or transformer is overloaded.

For an existing service, the NEC^® lets the maximum demand come from a year of utility demand data or, where that isn’t available, a 30-day load recording (NEC 220.87). That is often the difference between a costly service upgrade and finding out the capacity is already there.

A load study measures how much power is used. When the question is the quality of that power, such as harmonics, sags or transients, see power quality and harmonic studies.

Contact us for a free quote. We typically respond within one business day.

Main switchboard in an apartment building electrical room — **Main switchboard in an apartment building**

We perform electrical load analysis, sequence of operation and generator staged-loading designs, including bus transfer schemes and automated control schemes. A complete load assessment starts with an electrical load list and critical load profiles, so you know which loads must stay on, which can be shed, and in what order equipment can be restarted.

Commercial service switchboard with service conductors and line-side terminals

Residential load center with a surge protective device installed — **Load center with a surge protective device**

We assess your facility’s current capacity and the provisions available for future growth, and troubleshoot systems that trip, run hot or sag under load. Typical findings include unbalanced phases, transformers or feeders loaded beyond their rating, and spare capacity that was never documented. The results feed directly into electrical design for an expansion, or into short circuit and arc flash studies.

HMI & PLC Troubleshooting

PLC and HMI problems often look like electrical faults, and electrical faults often look like control problems. We troubleshoot both sides: control power and grounding, I/O and wiring, communication between the PLC and HMI, and the field devices and signals behind them, such as 4-20 mA current loops. Our article on common causes of PLC control system failure covers where to start.

Residential Customers

Adding an EV charger, heat pump, shop equipment or a solar or battery system can push a home’s service past its rating. We perform residential load calculations to show whether your existing service can carry the new load or needs an upgrade, and we can investigate unexplained high electrical usage or nuisance tripping. See when to get a residential electrical load analysis.

How a Load Study Works

We collect your one-line diagrams, panel schedules, equipment lists and any utility demand data, and record loads on the service or key feeders where the data isn’t enough. From that we calculate connected and demand loads, phase balance and the loading of each transformer, feeder and panel, and report the remaining capacity with recommendations, PE-stamped where required.

Open panelboard with main breaker, branch breakers and neatly routed branch circuit conductors

We serve Texas, Louisiana, Oklahoma, New Mexico, Colorado and Florida, and work nationwide.

When you contact us, you talk directly with an electrical engineer who can discuss your project. Our licensed Professional Engineers have active and past licensure in multiple states, our offices are in Coldspring, Texas and Westcliffe, Colorado, and we work nationwide. Deliverables are PE-stamped where required.

Contact us for a free quote. We typically respond within one business day.

NEC 220.87 load study Illustrative

Why a 30-day recording can miss the year’s peak

Under NEC 220.87 (120.87 in the 2026 NEC) the existing load can come from a year of demand data or, when that is not available, a recording of at least 30 days. Move a 30-day recording through one illustrative year and see what it finds, and what it misses.

Fig. 1One year of 15-minute demand on an 800 A serviceIllustrative

Each day’s highest 15-minute demand, under 400 A to over 600 A30-day recordingIts highest dayThe year’s highest day

Recording startsApr 1 to Apr 30

Arrow keys move the recording by one day, Page Up and Page Down by a week. You can also tap a day in the calendar.

Start the recording in

Highest day in the window, Apr 28: 15-minute averages

The 220.87 demand test: 125 percent of the highest demand plus the new load

125 percent of the highest demandNew load, 120 AOver the ratingService rating, 800 A

As recorded, this 30-day window meets the 220.87 demand test, but a full year of data does not: the year’s highest demand, 628 A on Aug 13, falls outside the window. 237 of the 336 windows you could pick in this year would meet the test as recorded. That is why the code requires the larger of the heating or cooling load to be included, by measurement or by calculation.

Highest 15-minute demand in the recording: 441 A Apr 28, 14:00 to 14:15
Highest in the full year: 628 A Aug 13, 16:15 to 16:30
Recording: 1.25 × highest + 120 A: 671.25 A Meets the demand test 128.75 A under the 800 A rating
Full year: 1.25 × highest + 120 A: 905 A Fails the demand test 105 A over the 800 A rating

Highest 15-minute demand in each month

Month	Highest demand	Day and interval
Jan	511 A	Jan 21, 07:45 to 08:00
Feb	459 A	Feb 5, 07:30 to 07:45
Mar	437 A	Mar 6, 13:45 to 14:00
Apr	441 A	Apr 28, 14:00 to 14:15
May	476 A	May 22, 14:15 to 14:30
Jun	548 A	Jun 24, 16:30 to 16:45
Jul	569 A	Jul 21, 17:00 to 17:15
Aug	628 A	Aug 13, 16:15 to 16:30
Sep	545 A	Sep 1, 17:00 to 17:15
Oct	463 A	Oct 1, 14:15 to 14:30
Nov	433 A	Nov 10, 14:30 to 14:45
Dec	483 A	Dec 9, 07:30 to 07:45

Illustrative data, not from a site. Demand is shown as the 15-minute average current on the highest loaded phase of an 800 A service, with a 120 A new load calculated separately. The code defines the 30-day demand in kilowatts; a real recording logs current or power on that phase, and amperes and kilowatts are converted with the measured voltage and power factor.

What 220.87 asks for

The existing load is the actual maximum demand: a year of demand data or, when that is not available, a continuous recording of at least 30 days on the highest loaded phase. The maximum demand is “the highest average kilowatts reached and maintained for a 15-minute interval.” 125 percent of it plus the new load must not exceed the ampacity of the feeder or the rating of the service, and the feeder and service must also have the overcurrent and overload protection that 240.4 and 230.90 require. This explainer shows only the demand test. The wording follows the 2020 and 2023 editions; check the one your AHJ enforces.

Why 30 days can miss the peak

A building’s highest demand usually comes on a few hot afternoons or cold mornings. Thirty days in spring or fall will not see them. So the recording has to be taken while the building is occupied, and it has to include the larger of the heating or cooling load, by measurement or by calculation.

How we set the recording

We time the recording to catch the facility’s normal peak operation. Where the season cannot be recorded, we add its load by calculation and show the method in the report. The 30-day route is not allowed on a feeder or service with PV, wind or any form of peak load shaving.

Frequently Asked Questions

What is an electrical load analysis?

A study of how much electrical capacity a building or system is using compared with what its service, transformers, feeders and panels are rated for, and how much is left for new equipment.

Can a load study avoid a service upgrade?

Sometimes. Measured demand is often lower than a calculation from nameplates suggests, and the NEC allows a year of demand data or a 30-day load recording to establish the existing load (NEC 220.87).

How long is a load recording?

Where utility demand data isn’t available, the NEC method uses a recording of at least 30 days. We set the recording period to capture your facility’s normal peak operation.