Navigate the complexities of EV charger load calculations. See how our electrical load calculator helps you stay compliant and efficient in the evolving electrical landscape.
As an electrician, you've likely noticed the surge in electric vehicle (EV) ownership. EV chargers, part of the broader category of electric vehicle supply equipment (EVSE), are becoming popular in homes across the country.
This shift comes with new challenges for electricians. When it comes to passing residential inspections, electricians have to properly account for EVSE in calculating electrical load.
This shift comes with new challenges for electricians. When it comes to passing residential inspections, electricians have to properly account for EVSE in calculating electrical load.
The EVSE load calculation challenge
Picture this: you're working on a residential load calculation for a client who's just bought a shiny new electric car. They want to install an EV charger, and now you're faced with a tricky question: how do you incorporate this EVSE into your electrical load calculation?
It's not just you — there's been quite a bit of discussion in the electrician community about the best way to handle EVSE loads. And to make things more interesting, there's some variance across different regions. But don't worry, we've got your back.
It's not just you — there's been quite a bit of discussion in the electrician community about the best way to handle EVSE loads. And to make things more interesting, there's some variance across different regions. But don't worry, we've got your back.
What the experts say
At Kopperfield, we've been listening closely to our network of electrical contractors and inspectors. Thousands of pros have used our electrical load calculator, and we've gathered tons of feedback. Here's what you need to know:
1. Treat EVSE load as a continuous load.
2. Include the EVSE load in the final calculation at 100%, not 40%.
1. Treat EVSE load as a continuous load.
2. Include the EVSE load in the final calculation at 100%, not 40%.
Let's break these down.
Why Consider EVSE as a continuous load?
Here's the deal: Article 100 of the National Electrical Code (NEC) defines a continuous load as one where the maximum current is expected to persist for three hours or more. Think about how long it takes to charge an EV on a home charger. You guessed it... typically longer than three hours.
This means we need to calculate EVSE at 125% of its rated load, as outlined in NEC 210.19(A). As Mike Holt put it in Electrical Construction & Maintenance (EC&M) Web:
This means we need to calculate EVSE at 125% of its rated load, as outlined in NEC 210.19(A). As Mike Holt put it in Electrical Construction & Maintenance (EC&M) Web:
"It's expected that an EV will take more than 3 hr to charge, so you must consider any electric vehicle charging load to be continuous [625.14, 2011 NEC]. Because these loads are continuous, it follows that overcurrent protection for supplying electric vehicle supply equipment must have a rating of not less than 125% of the maximum load of the electric vehicle supply equipment.”
The 2023 NEC doubles down on this in section 625.41. It states that overcurrent protection for feeders and branch circuits supplying EVSE should be sized for continuous duty. When non-continuous loads are on the same feeder, the overcurrent device needs to be rated for at least the sum of the non-continuous loads plus 125% of the continuous load.
Why include EVSE at 100% in final calculations?
Now, this is where things get a bit more complicated. Some folks argue that EVSEs should be treated as "appliances fastened in place" and lumped in with other "additional load" items, calculated at 40% after the first 8,000 VA. This argument stems from the fact that section 220.83(A) doesn't specifically address how to handle EVSE loads.
However, we've heard time and again from electricians that their authorities having jurisdiction (AHJs) require including the EVSE load at 100%, separate from additional loads.
The 2023 NEC clears the air in section 220.57, stating that EVSE should be included at a minimum of 7,200 VA or 100% of the nameplate rating.
However, we've heard time and again from electricians that their authorities having jurisdiction (AHJs) require including the EVSE load at 100%, separate from additional loads.
The 2023 NEC clears the air in section 220.57, stating that EVSE should be included at a minimum of 7,200 VA or 100% of the nameplate rating.
How Kopperfield's electrical load calculator can help
To make your life easier and ensure you're on the right track, our electrical load calculator defaults to:
1. Calculating the EV charging load at 125%
2. Including the EV charging load at 100% in the final calculation
Let's look at a real-world example: say you're dealing with a nominal input voltage of 48A for a charger at 240V. Our calculator would crunch the numbers like this: 48A x 240V x 125% = 14.4kVA.
But we know every job is unique, and AHJs can have different requirements. That's why we've built in flexibility. You can easily adjust the inclusion percentage in our "final calculation" module to match your specific needs, whether that's 40% or any other value your AHJ requires.
1. Calculating the EV charging load at 125%
2. Including the EV charging load at 100% in the final calculation
Let's look at a real-world example: say you're dealing with a nominal input voltage of 48A for a charger at 240V. Our calculator would crunch the numbers like this: 48A x 240V x 125% = 14.4kVA.
But we know every job is unique, and AHJs can have different requirements. That's why we've built in flexibility. You can easily adjust the inclusion percentage in our "final calculation" module to match your specific needs, whether that's 40% or any other value your AHJ requires.
Taking action: perfecting your EVSE load calculations
With this knowledge, you're ready to tackle EVSE load calculations like a pro! Here's what you can do:
1. Review your current load calculation process and see how it aligns with these guidelines.
2. If you haven't already, give Kopperfield's electrical load calculator a try. It's been tested and received great reviews by thousands of electricians!
3. Stay informed about the latest NEC updates and keep an ear out for any specific requirements from your local AHJ. Speaking of which, have you tried our National Electrical Code online chatbot yet? Our National Electrical Code online chatbot can help you quickly reference the latest code and look up calculations.
4. Share this knowledge with your fellow electricians, so we can build momentum for the entire industry.
Remember, mastering EVSE load calculations isn't just about compliance — it's about ensuring safe, efficient installations for your clients. As more and more homeowners switch to electric vehicles, your expertise in this area will become increasingly valuable.
1. Review your current load calculation process and see how it aligns with these guidelines.
2. If you haven't already, give Kopperfield's electrical load calculator a try. It's been tested and received great reviews by thousands of electricians!
3. Stay informed about the latest NEC updates and keep an ear out for any specific requirements from your local AHJ. Speaking of which, have you tried our National Electrical Code online chatbot yet? Our National Electrical Code online chatbot can help you quickly reference the latest code and look up calculations.
4. Share this knowledge with your fellow electricians, so we can build momentum for the entire industry.
Remember, mastering EVSE load calculations isn't just about compliance — it's about ensuring safe, efficient installations for your clients. As more and more homeowners switch to electric vehicles, your expertise in this area will become increasingly valuable.
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