The 17 largest insurers "are the primary drivers of the overall decline," the study said.
Overall satisfaction fell by "a significant seven points," J.D. Power said in a statement.
But satisfaction with smaller insurers increased. This is the first time in six years that small insurers achieved a higher satisfaction score than large insurers.
"The price factor is the largest advantage small insurers have over large insurers," the study said, along with more "personal interactions."
But larger insurers perform higher in digital interactions, including online assistance.
"The overall decline is largely influenced by a three-point decrease in price satisfaction," the study noted.
However, researchers said the "perception among some customers is that they have had an insurer-initiated increase, even though they have not experienced a specific incident or life change that could account for the price hike."
Some of the highest-ranked auto insurance brands by region include Ameriprise in California, Amica Mutual in New England, Geico in New York and Texas Farm Bureau Insurance in Texas.
Edmunds says: Car shoppers weighing their alternatives when it comes to auto insurance get some critical feedback from other consumers in this new study.