It’s been roughly eight years since Tesla unveiled the Semi in 2017. Series production of the truck is expected to begin this year, and the manufacturer has just teased the Semi’s DC fast-charging performance.

Tesla Semi Charging: 1.2 MW (1,200 kW)

A new short video shows the start of a DC fast-charging session on a “Semi Megacharger”. Within about 30 seconds, the power output gradually increases from 0 to 1,206 kW. That’s 1.2 megawatts.

Engineers hitting 1.2MW on Semi Megacharger pic.twitter.com/QtXyTgW0XC

— Tesla Semi (@tesla_semi) December 31, 2025

A power of 1.2 MW is a high level, a few times higher than in all-electric cars in the US (usually up to roughly 400 kW). However, for electric trucks, it’s both a necessity and a precursor to even higher power.

Tesla Semi: MCS Charging Port

The Tesla Semi features a Megawatt Charging System (MCS) charging port. The MCS is a relatively new standard that will be used worldwide for charging large EVs, such as trucks.

The MCS connector is larger and withstands higher power than CCS1/CCS2 or NACS (SAE J3400) connectors. It can be used for charging at up to 3 MW, although the exact power depends on the charger and the vehicle.

Tesla starts from a 1.2 MW level using its V4 Spercharger power electronics cabinet (which has a power output of 1.2 MW). The charging dispenser for the Semi features MCS and can utilize the full power of the V4 charger.

Tesla plans to build 46 Megacharger sites by early 2027, so within about one year from now. Partners’ charging stations will come in addition to that.

Tesla Semi: DC fast charging using a MCS connector at up to 1.2 MW. (Source: Tesla)

The same V4 charger is also used on the Supercharging network (the first public site launched in September 2025), although the V4 Supercharging stalls for cars feature NACS (SAE J3400) connectors. Up to eight NACS stalls can be connected to one 1.2 MW charger. Power is dynamically allocated between the stalls, up to 500 kW per stall.

Tesla Semi Range Replenishment Rate

According to Tesla Semi specs, the truck will be available in two versions, with up to 300 miles and 500 miles of range. Tesla promises fast-charging performance: “Up to 70% of range in 30 minutes”.

If we assume 70% of 500 miles, that means 350 miles of range can be replenished in 30 minutes. This brings us to an average of 11.7 miles/minute (likely higher at the beginning). Not many cars can replenish their range so quickly.

Tesla Semi Battery: 850 kWh (est.)

Initially, Tesla said that the Semi’s energy consumption is less than 2 kWh per mile. However, as development progressed, the production version was promised to achieve 1.7 kWh per mile.

Assuming 500 miles of range, the truck should be equipped with a massive 850-kWh battery pack (Tesla rarely discloses battery capacity). That would be a noticeable improvement over the previously used 900-kWh battery.  The smaller battery version with 300 miles of range would require a 510-kWh battery, using the same metric.

It’s believed that the production version of the Tesla Semi will use 4680-type cylindrical battery cells.

The redesigned Tesla Semi. (Source: Tesla)

Tesla Semi C-Rate

If we consider an 850-kWh battery version and 1.2 MW (1,200 kW) charging power, we can estimate the C-rate*. It’s 1.41C, so not too high.

We know that the C-rate for commercial vehicles and pickups is usually much lower than for cars.

*Info: The peak capacity rate (or C-rate) indicates the correlation between the charging power and the battery pack capacity. A value of 1C would mean that the power value in kW is equal to the battery pack capacity in kWh, and that at such a power (current) rate, the battery would be fully recharged in 1 hour. The higher the C-rate, the higher the load on the battery and the faster it charges. A flat 2C would translate to a 30-minute charging session (0-100% state of charge).

We assume Tesla can increase the Semi’s charging power, though it would require even more powerful chargers. The bottleneck appears to be related to the infrastructure rather than the vehicle itself.

Tesla Semi Video

The Tesla Semi will be produced at Tesla’s new facility (Giga Semi), near Tesla Giga Nevada. The Zanegler Tesla Semi Advocate recently published an exclusive drone video from the site, in which we can see the redesigned Tesla Semi at a charging stall.