Just 1.5% of electric vehicles (EVs) and plug-in hybrid vehicles (PHEVs) have needed their batteries replaced since 2011, according to a new study.

The U.S. Department of Energy used data from Recurrent, a company that tracks battery life. Recurrent tracks battery health directly for tens of thousands of PHEV and EV owners, giving it unique insight into the lifespan of a battery. Their services include a battery life report, acting much like a vehicle history report for batteries.

The battery is the most expensive part of any electric vehicle, and many potential EV buyers have cited fears about battery replacement costs as a reason to hold back.

Related: These EVs Need Their Batteries Replaced Most Often

Batteries have grown more reliable in recent years. The Energy Department explains, “replacement rates due to failure were well under 1%” for cars from model years 2016 and later. “Most of those would have been covered by the manufacturer’s warranty,” the report notes.