If you have ever filled a car with gasoline, you already understand the core concept of EV charging. You connect the vehicle to an energy source, energy flows in, the vehicle uses it later. That is the whole idea.
The difference is in the mechanics, and in the choices. Every gasoline pump is roughly interchangeable: same liquid fuel, a couple of grades, a few minutes at the nozzle. With EV charging, the speed of the fill, the connector that fits, the price per unit of energy, and the chemistry inside the pack all vary by orders of magnitude depending on where and how you plug in.
This article is the orientation: what is actually happening when an EV charges, what the levels mean, and which choices change your day.
What “charging” actually means
When you press the trigger on a gasoline pump, you are transferring chemical energy stored in liquid hydrocarbons into the car’s fuel tank. The car later burns that fuel to release the energy.
When you plug in an EV, you are transferring electrical energy from the grid (or a battery, or a solar array) into the car’s battery pack. The car later releases that energy through the motor.
The energy unit for a battery is the kilowatt-hour (kWh), and it is the number on the car’s spec sheet under usable capacity. The rate of flow during charging is measured in kilowatts (kW). Time is what connects the two:
Energy delivered (kWh) = Power (kW) × Time (hours)
A 7 kW Level 2 charger running for 8 hours moves about 56 kWh into the battery. The same battery on a 150 kW DC fast charger would need roughly 22 minutes for the same energy, except that real fast-charging sessions taper, so the arithmetic flatters the outcome. kW vs kWh explained is the deeper treatment, and it is worth reading early, because kW and kWh answer different questions and swapping one for the other silently changes the answer.
The three levels of charging
Charging is grouped into three power tiers, and the boundaries are not arbitrary. Each one sits at a different piece of electrical infrastructure.
Level 1: 120V household outlet
Plug an EV into a standard North American wall outlet and it draws about 12 amps at 120V, which is roughly 1.4 kW. That is slow. A 60 kWh battery would need more than 40 hours to fill from empty.
Level 1 is not useless. It suits:
- Plug-in hybrids, whose small packs refill overnight without effort
- Drivers whose daily distance is short enough that they never approach empty
- Anyone with no dedicated charging circuit available
It is the only level that requires no installation at all. An existing outdoor outlet is the entire setup.
Level 2: 240V dedicated circuit
Wire in a dedicated 240V circuit, the same class used for a clothes dryer or an electric range, and delivered power lands somewhere between 3.3 and 19.2 kW. Which end you get is set by the breaker rather than by the charger’s marketing: continuous-load rules cap sustained draw at 80% of the circuit rating, so a 40A circuit yields about 7.7 kW and a 60A circuit about 11.5 kW. A 60 kWh battery on a 7 kW feed fills in roughly 9 hours, which is what makes overnight charging work at all.
This is the workhorse tier. Home garages, workplace lots, and destination parking such as hotels and shopping centres all sit here.
The circuit itself is a licensed electrician’s job, and the bill is driven less by the charger than by the run from the panel to the parking spot and whether that panel has a spare slot. What a Level 2 home charger install actually costs (coming soon) breaks down where the money goes.
Level 3: DC fast charging
This is a different category, not “Level 2 but bigger”. DC fast chargers move the AC-to-DC conversion out of the car and into the station, then feed DC straight to the pack. Cabinet ratings start around 50 kW and run up into the hundreds.
A 60 kWh battery on a 150 kW charger goes from 20% to 80% in roughly 25 minutes, which is what makes road trips practical. The caveats matter more than the headline number:
- The session runs at the lowest cap in the chain. A car with a 50 kW DC limit draws 50 kW at a 350 kW station.
- Past roughly 80% state of charge the car deliberately requests less current to protect the cells. The last 20% can take as long as the first 60.
- Energy from a DC fast charger costs more per kWh than energy from a home circuit, because the price has to recover the cabinet, the grid connection, and the utility’s demand charges on top of the energy itself.
That cost structure is also why DC hardware clusters where utilisation is high, along travel corridors and in dense urban areas, rather than spreading evenly across a map.
The connector question
Even when a station has the right power level, the plug has to fit. The connector standards in current use:
| Connector | Region | Use |
|---|---|---|
| J1772 (Type 1) | North America | Level 1 and Level 2 AC only |
| Type 2 (Mennekes) | Europe | Level 1 and Level 2 AC only |
| CCS Type 1 | North America | AC and DC fast |
| CCS Type 2 | Europe | AC and DC fast |
| CHAdeMO | Japan, legacy elsewhere | DC fast only |
| NACS (SAE J3400) | North America | AC and DC fast |
The connector Tesla originally developed for its own vehicles was handed to SAE and standardised as J3400, which is why the same physical plug now appears under a vendor-neutral name. The NACS and J3400 switch explained (coming soon) covers what standardisation did and did not change.
The useful question is never “which connector is winning” but “will this specific car charge at this specific station”. Two things settle it: whether the pins mate, and whether both sides speak the same charging protocol across those pins. Adapters solve the first problem, not the second. That is why a passive adapter can bridge NACS and CCS Type 1, which share a DC protocol underneath, while nothing that simple bridges CHAdeMO and CCS. Will my EV charge at that station walks through the check, and the connector compatibility checker resolves the pairings for you.
What actually happens during a charging session
Walk through a typical session:
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Plug in. The connector locks, and the car and station run an electrical handshake. Both sides confirm the plug is seated, the voltage is right, and there is no short or grounding fault.
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Authenticate. On a private charger this step is trivial, because it is your charger. A public charger needs proof that someone will pay: an app tap, an RFID card, a contactless card at the terminal, or Plug & Charge, where the car presents a certificate over ISO 15118 and the driver does nothing at all. RFID vs Plug & Charge vs app authentication (coming soon) compares what each method costs you in reliability.
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Negotiate. The car states the voltage and current it can accept right now. The station states what it can deliver. They settle on a rate, and that rate keeps changing for the rest of the session.
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Charge. Energy flows from the grid, through the station, into the pack. On AC charging the car’s onboard charger converts AC to DC before storage. On DC fast charging the station has already done the conversion and delivers DC directly.
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Taper. As the battery fills past about 80%, the car requests less and less power, protecting the cells. By 95% the rate may be a fraction of the peak. By 100% it is barely a trickle.
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Stop and unplug. When the car reaches its target state of charge, or the driver disconnects, the session closes and a record lands in the driver’s app.
Almost none of this is visible from the driver’s seat. You plug in, you wait, you leave. The sequence earns its keep when a session fails, because where it fails tells you who to call: a handshake that never completes points at the cable or the vehicle, while a session that never starts after a successful handshake points at the account or the network behind it.
The energy itself takes a different path depending on charging level:
flowchart LR
Grid([Power grid AC]) --> Station[Charging station]
Station -->|Level 1 or 2: AC out| CarAC[Car onboard charger<br/>AC to DC]
Station -->|DC fast: converted in station| CarDC[Direct DC]
CarAC --> Battery[(Battery pack DC)]
CarDC --> Battery
Battery --> Motor((Electric motor))
style Grid fill:#fef3c7,stroke:#d97706
style Battery fill:#dbeafe,stroke:#2563eb
style Motor fill:#dcfce7,stroke:#16a34aThe key point: DC fast charging is faster because it bypasses the car’s onboard AC-to-DC converter. That converter is the ceiling on AC charging. A Level 2 station rated far above the car’s onboard charger still delivers only what the onboard charger is rated for, and that rating is printed on the vehicle’s spec sheet rather than the station’s.
The number that matters: kWh, not “minutes”
“How many minutes does it take to charge” is the first question everyone asks, and on its own it has no answer. Charging delivers energy. Minutes only mean something once you also state the power level and the size of the gap you are filling.
The right framing: to add X miles of range you need X divided by the car’s miles per kWh. At a given charging rate in kW, the time is that energy divided by the rate.
Example: a car averaging 3.5 mi/kWh needs 200 more miles. That is 200 ÷ 3.5, about 57 kWh. At 100 kW, 57 ÷ 100 = 0.57 hours, or 34 minutes, before any taper. Efficiency in kWh per mile (coming soon) is where that first number comes from, and it is not a fixed property of the car: it moves with speed, temperature, and load.
The charging time calculator handles the arithmetic, taper curve included.
The cost story
Per mile, the cost of charging is one multiplication, and every input is something you can look up yourself:
Cost per 100 miles = (100 ÷ miles per kWh) × price per kWh
Run it once for your home tariff and once for the public session price actually on offer. Take a car doing 3 mi/kWh: 100 miles needs about 33 kWh, so at a hypothetical $0.15/kWh overnight rate that is roughly $5, and at a hypothetical $0.50/kWh DC session rate it is roughly $17. The gasoline comparison has the same shape, (100 ÷ MPG) × price per gallon, so the two sit side by side cleanly.
What the arithmetic exposes is that fuel cost is mostly a question about where, not what. The same car on the same route in the same week can land several times apart depending on whether the energy came from a home circuit overnight or a highway cabinet at midday. The two prices are built differently: a residential tariff prices energy, while a public DC session price also has to recover hardware, the grid connection, and demand charges.
The EV vs gas cost calculator runs both sides on your own inputs.
What you actually need to know
Two ideas carry most of the weight.
Charging is a scheduling problem, not a refuelling problem. The question is not how fast the station goes, it is whether the car holds enough energy by the time you need it. A vehicle parked for nine hours has a nine-hour charging window, and 1.4 kW across that window is still 12 kWh, however slow it feels while you watch it. Fast charging becomes the answer only when the parking window is shorter than the energy you need.
Every advertised kW is a ceiling, not a promise. A session runs at the lowest of four limits: the station’s rating, the cable’s rating, the car’s onboard charger or DC limit, and what the pack will accept at its current state of charge and temperature. Any of them can be the binding constraint. The pack’s limit is the only one you cannot read off a label, and it is the one that moves while the session is running.
Put those together and a slow session stops looking like a malfunction. Two identical cars at the same 350 kW station can pull very different power on the same afternoon, because they arrived at different states of charge and different pack temperatures, and neither driver did anything wrong.
What we cover next
Specific topics get their own deep dives:
- kW vs kWh explained: the unit confusion that catches everyone
- Level 1 vs Level 2 vs DC fast charging: when each one fits
- EV charging connectors explained: J1772, CCS, NACS, CHAdeMO, Type 2
- AC vs DC charging explained (coming soon): the engineering behind the speed difference
- How long to charge an EV: realistic timings with the taper curve
- OCPI vs OCPP vs ISO 15118: what makes charging networks talk to each other
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