Finding a fast charger in the U.S. just got a lot easier for a lot of electric-car drivers. 

Two of America's largest fast-charging networks announced an agreement Thursday to allow each other's users to charge at their charging sites without signing up for new memberships or payment plans.

Electrify America and EVgo agreed to a roaming partnership that will allow members of either service to charge at any EVgo or Electrify America charging station.

Each of the networks already has individual agreements with the nation's other largest networks, ChargePoint and Greenlots. 

Electrify America DC fast chargers in Gulfport, Mississippi

Electrify America DC fast chargers in Gulfport, Mississippi

Together they make up at least 42 percent of the DC fast chargers in the U.S. and 60 percent of the total fast-charging locations, according to data from the Department of Energy's Alternative Fuels Data Center. The others are split among Tesla (with 52 percent of the total fast chargers in 22 percent of locations), and six smaller networks.

That means that drivers of EVs other than Teslas are have a widespread network in many ways on par with Tesla's Superchargers that they can use to top off their batteries.

Unlike Tesla's Supercharger network, however, EVgo chargers are concentrated in and around cities—where EVgo points out that most EVs drive—rather than along highways between cities where the chargers could allow drivers to make longer trips between cities, as Tesla's Superchargers do. 

Electrify America 350 kw chargers at Home Depot in Chicopee, Mass.

Electrify America 350 kw chargers at Home Depot in Chicopee, Mass.

Electrify America, a division of Volkswagen, was founded under the settlement agreement over Volkswagen's diesel emissions cheating, and is required to install such highway charging stations. So far, however, it has only completed the first of four phases of a 10-year rollout plan.

Roaming "interoperability" agreements are becoming more common, making it easier for electric car-drivers to use a wider variety of chargers. 

This has led to a spate of recent announcements—many using the "One-Step Plug & Charge" label—including between Greenlots and  Electrify America and ChargePoint and Blink.