NEC 625 and load calculations for EV charger installs explained
NEC Article 625 is the section of the electrical code that governs EV charging equipment, and a proper load calculation is what determines whether a home's existing service can support a charger or needs an upgrade first. Get either wrong and the install fails inspection or, worse, overloads the service. For an electrician, EV charger installs are growing work, and handling them correctly means understanding what Article 625 requires and running an honest load calculation before promising a homeowner their panel can take a charger. The load calc is not a formality; it is what tells you whether you are doing a simple install or a service upgrade.
The quick answer
Article 625 covers electric vehicle charging equipment and its installation requirements, including the continuous-load treatment that EV charging demands. A load calculation evaluates the home's existing electrical demand against its service capacity to determine whether adding a charger's load fits within the service or pushes it over, requiring an upgrade. The honest sequence is: run the load calculation, determine whether the service supports the charger, and only then quote the job, either a straightforward charger install or a charger plus the service upgrade the calculation showed was necessary. Skipping the load calc and assuming the panel can handle it is how installs fail and services overload.
Why EV charging is treated as continuous load
EV charging draws significant current for extended periods, which the code treats as continuous load, meaning the circuit and the calculation must account for sustained draw rather than brief peaks. This matters because a continuous load is sized more conservatively than an intermittent one, so an EV charger's effective demand on the service is substantial. An electrician who treats a charger like a normal appliance circuit underestimates its impact on the home's capacity, which is exactly the error that leads to overloaded services and failed inspections. Understanding the continuous-load treatment is central to handling EV work correctly under Article 625.
The load calculation is the decision point
The load calculation is where you find out what job you are actually doing. By evaluating the home's existing demand against its service capacity, the calculation tells you whether the charger's load fits or whether the service is already near its limit and needs upgrading. This is the difference between a charger install that drops into the existing panel and one that requires a service upgrade first, which is a much bigger, more expensive job. Running the calculation before quoting is what lets you tell the homeowner accurately what their install will involve and cost, rather than quoting a simple install and then discovering on site that the service cannot take it.
Why getting it wrong is costly
Skipping or fudging the load calculation has two bad outcomes. The install can fail inspection, because the inspector will check that the work complies with the code's load requirements, costing you a return trip and a frustrated homeowner. Or, worse, an undersized service gets a charger added anyway and operates overloaded, which is a safety hazard and a liability. Both outcomes trace back to not running an honest load calc up front. The calculation protects you from quoting wrong, failing inspection, and creating an unsafe condition, which is why it is the non-negotiable first step of any EV charger job rather than a box to check after the fact.
Setting the homeowner's expectations
EV charger inquiries often come from homeowners who assume adding a charger is simple and cheap, so part of handling these calls well is setting expectations honestly. The homeowner needs to understand that whether their install is straightforward or requires a service upgrade depends on their home's existing electrical capacity, which the load calculation will determine. Framing it this way upfront, we will run a load calculation to see whether your service supports the charger or needs upgrading, prepares the homeowner for either outcome and positions you as the electrician who does it right, rather than the one who quotes low and surprises them later.
Capturing and qualifying EV inquiries
EV charger work is growing and the inquiries are valuable, so capturing them and gathering the right initial information matters. An AI phone receptionist captures EV charger inquiries, gathers the home and electrical context that helps you scope the load calculation, and books the assessment through dispatch and booking, while setting the honest expectation that the install scope depends on the home's capacity. That early qualification gets the right information in hand before the visit, so the load calculation and the resulting quote, simple install or service upgrade, can be done accurately.
The bottom line
NEC Article 625 governs EV charging equipment, and a proper load calculation determines whether a home's service supports a charger or needs an upgrade first. EV charging is a continuous load that demands conservative sizing, so run the load calc before quoting, because it is the decision point between a simple install and a service upgrade. Skipping it leads to failed inspections and overloaded services, so make the honest load calculation the non-negotiable first step of every EV charger job.