“It creates confusion,” said Oleg Logvinov, chair for North America of the Charging Interface Initiative. The organization is a forum for manufacturers, equipment suppliers and charging companies using the main rival to Tesla’s standard, known as the Combined Charging System.

Buyers, Mr. Logvinov added, “will probably wait until you can figure out which one wins.”

Ford, G.M. and most manufacturers other than Tesla have been building cars with C.C.S. plugs, which are the standard in Europe. Charging networks operated by companies like Electrify America and EVgo primarily offer C.C.S. plugs.

Tesla’s plug is lighter and easier to handle but fits only the company’s cars. Under the agreements with Ford and G.M., Tesla will offer an adapter early next year enabling cars from those manufacturers to connect to about 12,000 of its fast chargers in the United States. In 2025, Ford and G.M. plan to make models designed to take the Tesla plug without an adapter.

The combined clout of Tesla, G.M. and Ford effectively compels operators of charging networks to install Tesla plugs and may effectively render the C.C.S. plug obsolete — at least in North America — in years to come. Rivian, a smaller electric vehicle company, said last week that it would also switch to the Tesla plug, and other manufacturers are considering doing so, too.

“For us, it’s important to make sure charging is really accessible and easy for customers,” R.J. Scaringe, the chief executive of Rivian, said in an interview.

As the Tesla plug becomes dominant, people with cars designed to use the C.C.S. plug will become increasingly dependent on adapters that, for safety, are limited in how much voltage they can handle and will charge more slowly.

Tesla’s system is known for being easy to use and reliable, while C.C.S. chargers can be finicky. Frustration with the existing charging network is clearly one reason Ford and G.M. decided to throw in their lot with Tesla.