The Tesla Supercharging network maintained its near-perfect reliability in 2022, according to Tesla's most recent 2022 Impact Report.

The company says that the average uptime of Supercharger sites last year amounted to 99.95 percent (down marginally from 99.96 percent in 2021), but was higher than in 2018-2020.

That's sounds awesome and Tesla entitled this part of its presentation "Chargers that just work."

However, the key is the methodology. Tesla defines the uptime of Supercharger sites as the average percentage of sites globally that had at least 50 percent daily capacity functional for the year:

*Uptime of Supercharger sites reflects the average percentage of sites globally that had at least 50% of their daily capacity functional for the year.

In other words, in 2022, on average, 99.95% of the stations had at least 50 percent daily capacity (stalls, as we understand) fully functional for the year.

Average uptime of Supercharger sites*:

  • 2018: 99.94%
  • 2019: 99.90%
  • 2020: 99.74%
  • 2021: 99.86%
  • 2022: 99.95%

Well, we have all heard many times that the Tesla Supercharging network is one of the most reliable (if not the most reliable) fast-charging networks for all-electric vehicles, but this metric is a little bit controversial.

That's because if (in theory), up to 49.9 percent of the stalls at each station were dead for the whole year, and the remaining 51.1 percent would be up for the whole year, then the equation would return a result of a perfect 100 percent reliability.

Additionally, such a simple presentation does not really gives us an outlook into how many stations/stalls might be faulty.

We can do some math to estimate the reliability. For example, assuming 5,000 stations around the world (Tesla was pretty close to that number as of the end of Q1 2023) one station offline for the entire year would result in 99.98 percent reliability. Three down for the entire year would be 99.94 percent reliable.

If we additionally assume that instead of three particular stations down for the whole year, there are three different stations down every day, then we must multiply it by 365. That's 1,095 stations on average, which had one day in a year with less than 50 percent (0-49.9 percent) daily capacity functional.

This is still a great result because we are talking only about one day with less than 50 percent daily capacity at roughly one-fifth of the stations. Some stalls might be still available at those sites, while the rest of the stations would be running at more than 50 percent capacity.

Example for 99.94 reliability and 5,000 stations:

  • three stations offline (below 50% daily capacity) for the entire year
    4,997 stations: at least 50% daily capacity every day
  • 1,095 stations that were offline (below 50% daily capacity) one day in a year
    3,905 stations: at least 50% daily capacity every day

Other elements (like power output) or even the source of issues (they might be external) were not discussed.

It will be very interesting to see whether Tesla will be able to maintain a high uptime ratio in the future, considering the ongoing expansion of the network, and increasing complexity due to the addition of the non-Tesla Supercharging pilot (various EVs, app for non-Tesla vehicles, built-in CCS1 adapter in North America) and a higher utilization (more Tesla EVs per station/stall and additional non-Tesla EVs).

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