When charging, your EV is in constant communication with the DC charger station to determine how much power to draw. Ultimately, how fast your EV charges is influenced by several variables, including the ambient temperature (extremes are generally worse), battery temperature (a warm battery will be able to accept the most power), the current state of charge of the solar batteries (lower is better), the charging rate of the station and the acceptance rate of your vehicle. We’ll primarily focus on the latter two variables in this article.

A DC fast charging station’s charging rate is measured as its maximum output in kilowatts (kW). For light-duty vehicles, you’ll find stations ranging from 50 kW to as high as 350 kW, and generally speaking, the lower the kW, the slower the charge. However, choosing a higher-powered DC fast charger over a lower-powered one does not guarantee that you’ll charge more quickly. That’s where your EV’s acceptance rate comes into play.

An EV’s acceptance rate is the maximum amount of power it can take, also measured in kW. Consider the Chevy Bolt EV. The Bolt EV has an acceptance rate of 55 kW (considered quite slow today). That means that its peak charging rate would be approximately the same whether you stopped at a DC fast charger rated at 62.5 kW, 150 kW or 350 kW. The inverse is true as well. Even though a Porsche Taycan can charge at up to 270 kW (its acceptance rate), if you plugged in at a station rated at 150 kW, the vehicle wouldn’t be able to reach its peak.

Here are the acceptance rates of some other EVs:

Tesla Model Y: 250 kW

Tesla Model 3: 250 kW

Ford Mustang Mach-E: 150 kW

Audi e-tron: 150 kW

Volkswagen ID.4: 125 kW

Nissan LEAF SL Plus: 100 kW

Another important concept related to an EV’s charging speed is its DC fast charging curve. Every EV model has its own charging curve, which is basically how much power it pulls (and how many miles it adds) over time as it charges. Knowing your EV’s charging curve can be a big help, especially on longer trips, when deciding for how long to stay at a station. In many cases, it’s smarter to hop between chargers — stopping only briefly at each one — rather than lingering for a prolonged period at a given location.

Typically, an EV will charge at its maximum rate for only part of a charging session, usually in the lower half of the battery pack. For how long specifically depends on the vehicle. The one general constant across charging curves is a ramp down of charging speed at approximately 80% charge, which occurs to protect the battery.

Let’s take a look at the charging curve below from InsideEVs for the Volkswagen ID.4. The vertical axis shows the power being drawn by the EV in kW, and the horizontal axis is the current percent charge of the vehicle’s battery.