Glossary
EV charging glossary
Every term on this site, defined without using three other terms you would also have to look up.
By Sawyer V. · Published September 8, 2026
Alphabetical. If a term you met is missing, tell us and we will add it -- that is a genuinely useful thing to send us.
| Term | Plain English |
|---|---|
| Amp (A) | Electrical current. More amps means faster charging and thicker wire. See volts, amps and kW. |
| AC charging | Alternating current charging -- what happens at home. The car's onboard charger converts it to DC for the battery. |
| CCS | Combined Charging System. A J1772 inlet with two DC pins added beneath. Its AC section takes a normal J1772 home charger. |
| CHAdeMO | An older Japanese DC fast-charging standard, largely superseded. Some older Nissan Leafs use it. |
| Continuous load | A device drawing full current for three hours or more. EV chargers are one, which is why the circuit is sized at 125% of the draw. |
| DC fast charging | Public high-power charging that bypasses the car's onboard charger. Not possible at home. |
| EVSE | Electric Vehicle Supply Equipment -- the technical name for what everyone calls a charger. Strictly, the charger is inside the car. |
| GFCI | Ground Fault Circuit Interrupter. A device that cuts power when it detects current leaking to ground. See nuisance tripping. |
| Hardwired | A charger wired directly into the circuit rather than plugged in. Allows higher amperage. See hardwired vs plug-in. |
| IP rating | An international code for dust and water protection, e.g. IP67. Not a safety listing. |
| J1772 | The North American AC charging connector used by nearly every non-Tesla EV. See plug types. |
| kW (kilowatt) | Power -- charging speed. Amps x volts / 1000. |
| kWh (kilowatt-hour) | Energy -- the size of your battery, and what your electricity bill charges for. |
| Level 1 | Charging from a standard 120 V outlet. Roughly 3 to 5 miles of range per hour. |
| Level 2 | Charging from a 240 V circuit. Roughly 25 to 40 miles per hour. What people mean by a home charger. |
| Load calculation | The code procedure that determines whether your electrical service can carry a new charger. See load calculation. |
| Load management | A system that reduces charging when the rest of the house draws heavily, so you can add a charger without upgrading the panel. |
| mi/kWh | Your car's efficiency: miles traveled per kilowatt-hour. Typically 2 to 4. |
| NACS | North American Charging Standard, formally SAE J3400. Tesla's connector, now being adopted industry-wide. See NACS vehicles. |
| NEMA (enclosure rating) | A rating for protection against water and dust, e.g. NEMA Type 4. Not a safety listing. |
| NEMA 14-50 | A 240 V, 50 A four-wire receptacle used for ranges, RVs and plug-in chargers. Allows 40 A of charging. See NEMA 14-50. |
| NEMA 6-50 | A 240 V, 50 A three-wire receptacle with no neutral. Common for welders. Also allows 40 A. See NEMA 6-50. |
| NRTL | Nationally Recognized Testing Laboratory -- a body OSHA recognizes to certify products. UL, ETL and CSA are the ones you will see. |
| Onboard charger | The component inside the car that converts AC to DC. Its maximum sets your home charging speed, no matter how big the wall unit is. |
| Panel (service panel) | The breaker box. Its main breaker rating is your home's total electrical service. |
| Preconditioning | Warming or cooling the cabin and battery while plugged in, so the energy comes from the wall rather than the battery. |
| Service upgrade | Increasing your home's total electrical capacity, e.g. 100 A to 200 A. The most expensive part of a difficult install. |
| Subpanel | An additional breaker panel fed from the main one. Solves a shortage of breaker slots, not a shortage of capacity. |
| Tapering | The way charging slows as a battery approaches full, to protect the cells. |
| Time-of-use rate | An electricity tariff where the price varies by time of day. Charging off-peak is the biggest lever on your running cost. |
| UL listed | The finished device was evaluated by UL. Not the same as 'UL certified components'. See certifications. |
| Volt (V) | Electrical pressure. 120 V is a normal outlet; 240 V is a dryer circuit. |
FAQ
Questions people actually ask
What does EVSE mean?
Electric Vehicle Supply Equipment -- the formal name for what everyone calls a charger. Strictly the charger is inside the car; the wall unit supplies power to it.
What is an onboard charger?
The component inside the car that converts AC power from the wall into DC for the battery. Its maximum rating caps your home charging speed regardless of the wall unit's size.
What is the difference between NEMA as an enclosure rating and NEMA 14-50?
They are unrelated uses of the same organization's name. NEMA Type 4 is a weather-protection rating; NEMA 14-50 is a plug and receptacle configuration.
What does tapering mean in EV charging?
The way charging slows as the battery approaches full, to protect the cells. It is why the last 10% takes disproportionately long.
Sources
Where these numbers come from
- NEC Article 625: EV charging equipment — WireRefSource for EVSE, continuous-load and circuit terminology.
- All EVs with a NACS charging port in 2026 — SimpleSwitchSource for NACS / SAE J3400 terminology. Fetched 2026-09-08.
Read next
Related reading
- Volts, amps, kW and kWh, in plain EnglishThe four electrical terms that matter and the one formula that ties them together.
- EV plug types, explainedJ1772, NACS, CCS and CHAdeMO: which plug your car has and which matters at home.
- Level 1, Level 2 and DC fast charging: which one you needLevel 1, Level 2 and DC fast charging with real speeds, and which you need at home.
- EV charging basicsLevels, plugs, amps and kilowatts in plain English, plus how to work out what you need.