EV batteries now lose about 2.3% of capacity a year, and fast charging speeds it up

An electric-car battery loses a little of its usable capacity every year, and the fleet-wide rate of that loss has been measured again. Telematics company Geotab found an average of about 2.3% per year across more than 22,700 electric vehicles, and the pace was faster for cars that regularly charged at high power.

The analysis, released January 13, 2026, covers 21 makes and models and updates an earlier Geotab study, in which the average was 1.8% per year. At 2.3% a year, the company’s own blog projects a battery keeps roughly 81.6% of its capacity after eight years. The figures describe how batteries have aged in the data Geotab collects from its customers, and they sit alongside several other findings that matter more for how a car is driven day to day.

Fast charging above 100 kW

The clearest driver of extra wear in the data was charging power. Vehicles that used DC fast charging above 100 kW, and used it often, degraded by up to 3.0% a year, according to Geotab’s announcement of the study. Vehicles that mostly used AC or lower-power charging lost about 1.5% a year, so the heavy fast-charging group aged at roughly double the rate.

Geotab’s longer write-up turns that gap into an eight-year projection: about 88% battery health for the low-fast-charging group against about 76% for the high-frequency, high-power group. A 12-point difference in remaining capacity is a gap large enough to show up in a car’s usable range.

Why high power is harder on cells

The mechanism is known from laboratory work and is not new to this dataset. Argonne National Laboratory’s extreme-fast-charge project states that “at present, ultra-fast recharging seriously degrades battery life and poses safety hazards,” and names lithium plating on the graphite anode as the leading suspect: lithium from the electrolyte deposits as metal on the anode surface instead of sliding into it, permanently removing that lithium from circulation. The lab also lists rapid temperature rise and cracking of electrode particles among the problems.

Older field data pointed the same way at a lower power level. An Idaho National Laboratory test of four 2012 Nissan Leafs ran each car to 50,000 miles, with two charged on AC Level 2 and two on a 50 kW DC fast charger, twice a day. The Level 2 cars retained about 75% of their original capacity, and the fast-charged cars about 72%, a gap of roughly three percentage points.

Heat, mileage, and the 80% rule

Geotab measured several other factors, and none was as large as fast charging. Cars in hot climates, defined as more than 35 days a year above 25 degrees Celsius, lost capacity about 0.4% per year faster than those in mild climates. Vehicles with high utilization, charging more than 35% of the battery’s capacity daily, degraded about 0.8% faster than those below 15% daily, a cost the company frames as an acceptable trade for fleets that earn money from the miles.

The study also questions a common habit. Geotab reports that modern EVs carry built-in protective buffers, so degradation accelerated significantly only when vehicles spent more than 80% of their time at very high or very low states of charge. For a typical driver, the popular advice to stop at 80% every time is not what the data flags as the main risk.

“EV battery health remains strong, even as vehicles are charged faster and deployed more intensively,” said Charlotte Argue, Senior Manager, Sustainable Mobility at Geotab. The company’s release attributes the rise from 1.8% to 2.3% to “changes in how EVs are being used, most notably a growing reliance on high-power DC fast charging.” Argue added a practical corollary aimed at fleets: “Using the lowest charging power that still meets operational needs can make a measurable difference.”

Even the 2.3% average leaves batteries in reasonable shape by the standards federal researchers use. The Department of Energy’s Alternative Fuels Data Center says studies have shown an EV battery could have at least 70% of its initial capacity left at the end of its life, provided it has not failed or been damaged. At Geotab’s 3.0% rate, the eight-year projection of about 76% remaining stays above that line.

The sample has limits. It is drawn from vehicles carrying Geotab’s telematics, the release does not say how many are fleet cars and how many are privately owned, and the gap between 1.5% and 3.0% describes groups of cars sorted by charging behavior rather than a controlled experiment on one battery. Geotab’s release and its blog agree on the main figures. What neither answers is how much of the annual loss an individual car would recover if its owner traded the fastest charger for a slower one.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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