One of the first questions I get asked about my Tesla is, "What happens when you need to replace the battery?" It's easy to brush off because there are plenty of facts regarding failure statistics, warranty, and even the cost should it happen. What people don't typically ask about is battery degradation.
It's a real thing with EVs, just like that iPhone you're reading this article on. As batteries age and go through charging cycles, they lose capacity. A new study by Recurrent digs into that data by studying 12,198 Teslas, and the report shows the cars are only achieving a fraction of their advertised EPA range well before most people pay off their loans.
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EV Battery Degradation
Battery degradation is a fact of life. However, some battery chemistries—like lithium iron phosphate (LFP) packs found in some Tesla models—are more susceptible to calendar aging than others. Either way, if you own an EV, don't expect perfect range forever.
Before we go any further, it's important to reaffirm that the study performed by Recurrent is based on data collected from their fleet. It specifically compares the range of the fleet data against the EPA rating, not the battery capacity retention over time or vehicle mileage.
Recurrent can pinpoint battery life using the data it collects from 7,078 Model 3s and 5,120 Model Ys. It used nearly 1.6 million observations (around 130 observations per vehicle) to determine the average fleet-wide range statistics in its report.
The data from Recurrent shows that after approximately three years (right around the 1,100-day mark), the average Tesla Model 3 and Model Y are achieving just 64% of their original EPA-rated range.
It's important to point out that the Teslas observed in Recurrent's study never actually appear to hit the advertised EPA range. Even at 0 miles, the cars only achieve between approximately 70% and 72.5% of their advertised EPA range. That means a zero-mile 2023 Tesla Model 3 Performance, rated by the EPA as having 315 miles of range, may be observed by Recurrent as achieving around 230 miles on a single charge based on the above charts.
This isn't a problem unique to Tesla. As Recurrent says, "The basic EPA testing protocol gets it wrong for all EVs." It doesn't factor in temperature changes or driving above 60 miles per hour, plus it allows for manufacturer adjustments.
The relevant factor to consider here is the delta between the range achieved by a new car with a fresh battery and how much range it still has after three years, agnostic of overall vehicle mileage as this point isn't plotted in the above charts. This figure appears to be between 6% and 8.5% before leveling off at the three-year mark—not too shabby, if you ask us.
Recurrent's data also shows that Teslas don't appear to be as affected by DC fast charging as some other brands, which is a plus for people who like to take long road trips or don't have access to Level 1 or Level 2 charging at home.
Following the publishing of this article, Martin Viecha, the current VP of Investor Relations at Tesla who last month announced he is stepping away from the company, responded to InsideEVs via a post on X with a chart showing a separate study performed by Tesla.
Tesla's study plots battery retention to vehicle mileage, whereas Recurrent's study plots the observed real-world range (compared to the EPA's estimated range) against the calendar age of a vehicle's battery.
The study posted by Viecha, while not an apples-to-apple comparison, does bring to light that Tesla shows an average retention of greater than 80% over 150,000 miles. InsideEVs asked Viecha for a comparison similar to the data in Recurrent's study and will update this article if the data is provided.
UPDATE 5/24/24 3:55 PM EST: This post was updated to include a response and additional data from Tesla's VP of Investor Relations, Martin Viecha.
