If you own a plug-in vehicle or are considering one, you’ve probably been exposed to the terms Level 1, Level 2 and Level 3 associated with charging speeds — not to be confused with the levels of autonomy, which are flawed and of questionable value. Honestly, the numbered charging levels aren’t perfect, either. Below we explain what they mean — and what they don’t. Bear in mind that regardless of the charging method, batteries always charge faster when empty and slower as they fill, and that temperature also affects how quickly a car will charge. All of the levels below apply both to Teslas and other brands, though Tesla has a proprietary connector and the rest of the industry has agreed upon the one known only as J1772 for the SAE International standard that rules all EV charging.
Level 1 represents 120-volt charging using the ubiquitous household outlet. It’s known as trickle charging because it typically provides 3-5 miles of range for every hour it’s connected to an EV or plug-in hybrid electric vehicle (PHEV). Modern PHEVs are EPA-rated with 15-60 miles of electric range, while EVs are between 150-400 miles, so that could mean 30 hours to replenish 150 miles of range at Level 1’s fastest. The amount depends mostly on the vehicle’s efficiency, because a less efficient vehicle gets less range from the same amount of electricity as a more efficient one.
Automakers almost always include with their plug-in vehicles a small Level 1 charger, a small box or cylinder with a short cord, and grounded household plug on one end and a longer cord and the pistol-grip connector that plugs into the car on the other. It’s technically called an EVSE, which stands for electric vehicle service equipment or supply equipment. While it’s the least useful charging level, Level 1 manages to be the most useful designation because there’s little difference in how much juice any of these chargers provide. Typically they’re limited to 10 or 12 amperes of current because there’s an assumption they’ll be used on a 15- or 20-amp circuit along with other electric outlets and, thus, other appliances. Ten versus 12 amps is a difference, but a trickle is still a trickle. You’ll see in the Level 2 description how meaningless a level can be.