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Most homeowners who add an EV charger think of it as a one-day project. Pick a charger, mount it on the garage wall, plug it in, done. The reality is that an EV charger pulls more sustained power than almost anything else in a home, and what happens in the planning stage matters far more than the install itself.
If you are weighing your options, our overview on installing an EV charger at home is a good starting point, and which EV charger is right for your home covers the buying side. This post goes deeper on what should be planned before the charger ever shows up on site.
This Is Not a Typical DIY Project
An EV charger is not comparable to swapping out a light fixture or adding a receptacle. These systems often run at 40 to 60 amps continuously for several hours at a time, and they are required to be installed under specific provisions of the National Electrical Code.[1]
Improper installation can lead to overheating, equipment failure, or fire risk. A homeowner who chooses to install one themselves should pull a homeowner’s electrical permit through the South Dakota Electrical Commission.[2] Unpermitted electrical work tied to a failure, especially a fire, can result in an insurance claim being denied.
The same principle applies to oversized breakers as a shortcut. We covered that in detail in why installing a bigger breaker is not the solution.
EV Chargers Are Continuous Loads (This Changes Everything)
Under the NEC, an EV charger is treated as a continuous load. A continuous load is one where the maximum current is expected to continue for three hours or more, and EV charging routinely runs six to ten hours overnight.
What the code says
NEC Article 625 covers electric vehicle power transfer systems.[1] NEC 210.19 and 210.20 require that branch-circuit conductors and overcurrent protection serving continuous loads be sized at 125 percent of the continuous load.[3] In practical terms, a 48 amp charger requires a 60 amp circuit, and that load can run for hours without interruption.
There are very few residential loads that behave this way. The closest comparison is large electric heating equipment.
Panel Capacity Matters More Than Most People Think
Before an EV charger goes in, the electrical system has to be evaluated. The questions we ask are:
- Is your panel already near capacity?
- Do you have other large loads, such as electric heat, a hot tub, or a workshop subpanel?
- Will adding the charger push the house past its allowable load calculation?
We perform a full load calculation under NEC Article 220 to answer those questions and to determine whether your existing electrical panel can handle the charger or whether a service upgrade is required first. If your panel is older or you are unsure about its condition, is my electrical panel safe and what homeowners should know about electrical panels walk through the warning signs.
Wire Size and Installation Method Are Critical
This is where a lot of installs go wrong, and it is also the part most homeowners never see.
A 60 amp EV circuit requires conductors rated for that load. Common residential NM cable (often referred to as Romex) is governed by NEC 334.80, which limits its ampacity to the 60°C column of the conductor temperature tables.[4] For 6 AWG copper, that ampacity is 55 amps. In many cases that is not sufficient for a full 60 amp EV circuit, and a different wiring method is needed.
Proper installations often use:
- 6 AWG copper conductors in MC cable or conduit (THHN or THWN) rated for higher temperatures
- Correct termination ratings at the breaker and at the charger
- Voltage drop calculations on longer runs
The materials matter at this stage. We have written before on how reliable the fixtures, devices, panels, and breakers we install are, and the same standard applies to EV circuits.
Hardwired vs. Plug-In Chargers
There are two common ways an EV charger can be connected to the home:
Plug-in (NEMA 14-50): The charger plugs into a 240 volt receptacle. The receptacle itself has to be properly rated for EV use, and not every 14-50 device on the market is. Lower-quality receptacles are a frequent failure point under sustained EV loads.
Hardwired: The charger is wired directly into the circuit, with no receptacle in between. This is more reliable long-term and is often required for higher-output units.
For long-term reliability, we typically recommend hardwired installations. We covered the trade-offs in more detail in hardwired or plug-in EV charger for your home.
Distance and Layout Affect Cost and Performance
The further the charger sits from the panel, the more expensive the installation becomes and the more important voltage drop calculations are. When we walk a job, we look at:
- Total run length from the panel to the charger location
- Routing complexity, including finished walls, attics, and crawlspaces
- Indoor vs. outdoor installation
- Mounting location, accessibility, and protection from impact
Solar, Generators, and Backup Power
Two questions come up often enough that they deserve their own section.
Can you run an EV charger on solar alone? Yes, with limits. A closed system (solar plus battery, no utility connection) can charge an EV if it is designed for it. That means adequate solar production, enough battery storage to handle a sustained charging load, and load management that prioritizes when the vehicle charges. In off-grid or closed systems, we generally recommend pairing the solar array with a backup generator so the vehicle can still charge when production and storage cannot keep up.
Can a backup generator run an EV charger? Yes, but only if the generator was sized with the EV in mind. A generator that was specified before the charger was added may not have the capacity to handle it, and other loads in the home may need to be shed during charging or charging speed may need to be reduced. In our generator installations, we leave headroom in capacity, but EV charging still needs to be a deliberate design decision rather than an afterthought.
For homeowners who are thinking about combining these systems, our solar, EV, and generators page walks through how they fit together.
Doing It Right the First Time
An EV charger is one of the largest electrical loads a homeowner will ever add to their house. The installation deserves the same level of planning as a service upgrade or a generator install, because in many cases that is exactly what is involved underneath it.
At Wires R Us we install EV chargers across the Black Hills region, from Rapid City and Spearfish through Sturgis, Belle Fourche, and Hot Springs. Every install starts with a load calculation, a look at the panel, and a clear conversation about what the home can handle today and what will need to change to support it.
If you are planning an installation, take a look at our EV charger installations page, or check the electrical FAQs for answers to common questions. Homeowners in the Black Hills can also visit our Rapid City EV charger installation page for local service details. When you are ready to talk specifics, contact us and we will walk through your home with you.
References
- National Fire Protection Association (NFPA). NFPA 70: National Electrical Code, Article 625, Electric Vehicle Power Transfer System. Available at nfpa.org/codes-and-standards/nfpa-70-standard-development/70
- South Dakota Electrical Commission, Department of Labor and Regulation. Electrical Permits and Licensing. Available at dlr.sd.gov/bdcomm/electrical/
- National Fire Protection Association (NFPA). NFPA 70: National Electrical Code, Articles 210.19 and 210.20, branch-circuit conductors and overcurrent protection for continuous loads (125 percent sizing requirement).
- National Fire Protection Association (NFPA). NFPA 70: National Electrical Code, Article 334.80, ampacity of nonmetallic-sheathed cable; ampacity values referenced to the 60°C column of the applicable conductor temperature table.
- U.S. Department of Energy, Alternative Fuels Data Center. Developing Infrastructure to Charge Plug-In Electric Vehicles. Available at afdc.energy.gov/fuels/electricity-infrastructure-development
This article is for general educational purposes. Electrical codes are updated periodically and local jurisdictions may adopt different editions of the NEC or apply additional amendments. For specifics on your home, consult a licensed electrical contractor.
