Electrical Load Calculation For A Service (2020 NEC)

Over the past 28 years in the trade, I’ve learned many different electrical load calculation methods. They all will work, but in my opinion, they are generally not easy to understand, and are typically not organized very well.

Don’t get me wrong; I certainly don’t mean to criticize the work others have put into their calc strategies. I learned a lot through them. But I always had the nagging feeling that there must be a better way.

So, I made it my aim to create a better method for calculating any service load. I hope you find it as helpful to your needs as it has been to mine.

I’ve developed this table-style approach, along with accompanying instructional videos, for two purposes:

• to help other electricians thoroughly understand the ins and outs of service calcs, showing every detailed step along the way
• to provide a simple, one-page template with all of the needed information and criteria included – to be used as a quick, in-the-field, real-world tool, and also as a worksheet and study guide for those preparing for licensing exams

Use the Table of Contents to quickly find the calc you need.

<– To see more calculation videos, visit my YouTube channel –>
Simply Electrical

There are many different types of service load calculations. I’ve sorted them into categories below for your convenience.

Residential Standard Method Electrical Load Calculations

One-family Standard Method

Crash Course:

Note: This SFR Crash Course video has three places where I made a mistake (it was my first video!). I have placed captioned subtitles at the appropriate time stamps to highlight the corrections.

Deep Dive:

Multifamily Standard Method

Crash Course:

Note: There are two mistakes in this Multifamily Crash Course video – one at the 8-minute mark, and one at about 15 minutes in. I have placed captioned subtitles there to highlight the corrections.

Deep Dive:

Duplex Standard Method

Crash Course:

Note: There is a typo at the 12-minute mark in this Duplex video. I placed a captioned subtitle at the time stamp to bring it to your attention.

Residential Optional Method Calcs

One-family Optional Method

Crash Course:

Deep Dive:

Multifamily Optional Method

Crash Course:

Deep Dive:

Triplex Optional Method

Crash Course:

Commercial Calcs

General Commercial Standard Method

Deep Dive:

Office building Standard Method

Crash Course:

Restaurant Standard Method

Crash Course:

Restaurant Optional Method

Crash Course:

School Building Optional Method

Crash Course:

<– To see more calculation videos, visit my YouTube channel –>
Simply Electrical

About the Calculation Tables

As stated briefly above, I created these tables to help folks in a number of different ways:

1. You get your entire calc on one single page, so you can see everything at once. This includes the actual problem with all of the given data.
2. Everything is in order from start to finish, with a logical flow from point to point.
3. Each category column is separate, so you can easily see the distinctions between load types.
4. All NEC code references are included, so you know where the data is coming from. That way, you can get a better understanding of exactly why we’re implementing each and every step in the process.

About the Videos

The videos are provided to walk you through each type of calc step-by-step, so that you can see exactly where the data is derived from, how it is employed in the table, and why we get the final result.

I apologize for the poor quality of audio on a few of the early videos. It was my first go at making a video and my equipment and settings were not dialed in. You’ll notice that the more recent ones have a bit better sound quality.

Also, some of the videos have minor errors (typo or wrong reference) that I didn’t catch before posting. Since YouTube doesn’t allow editing (without resubmitting the video and losing the accumulated stats), I have made captioned notes at each place (time stamp) that needed a correction.

Related Topics

Here are a few articles I’ve written about various electrical troubleshooting methods. As an electrician, you might find them helpful — either on the job, or for personal use. I’ll continue to add to these as I write more articles.

Read:
Why Does My Circuit Breaker Keep Tripping?
How To Tell If A Circuit Breaker Is Bad
Circuit Beaker Is On, But No Power? Here’s What To Check

Other Topics

I recently took over a DIY HVAC repair website created by an HVAC tech. Though I’m an electrician, HVAC is a closely related field, and the articles contain a lot of good information from a pro.

The only catch is that English was not his primary language (he used to live in Canada). So I’m in the process of cleaning them up a bit and smoothing out the writing a little.

Check out HVAC-Boss.com

Feel free to browse the site. There are over 500 articles covering all things related to furnaces, heat pumps, mini-splits, ventilation, water heaters, etc.

There have been many times throughout my career where I needed to work on HVAC equipment (replacing capacitors, relays, etc.), and this site would have been useful to me. Besides, understanding concepts in other trades boosts your overall troubleshooting IQ, and gives you a leg up on other electricians.

Never stop learning!