Solar-powered charging stations that boost smartphone batteries hit Somerville, Boston

They look like futuristic phone booths. But instead of stepping inside and dropping a quarter in a slot to make a call, people can plug in their smartphones to charge them, and then just walk away.

Both Somerville and Boston recently installed solar-powered charging stations for people’s handheld devices in busy parts of their respective cities.

Somerville placed WrightGrid’s sun-reliant stations in Davis Square, Union Square, and Ball Square as part of a two-month pilot that began earlier this month. The rollout of the stations was launched through the city’s GreenTech program, which offers energy-efficient businesses the chance to test “green products” in the community.

“We . . . are excited to be launching our first pilot program in the city where we got our start. We are grateful to have such a forward-thinking municipal partner,” said Ryan Wright, WrightGrid’s founder, in a statement.

Boston introduced WrightGrid’s technology to two locations at City Hall Plaza Tuesday, as part of a similar pilot program sponsored by Mayor Martin J. Walsh’s office and Babson College.

“The addition of WrightGrid’s solar-powered mobile charging stations to City Hall Plaza will help us offer people yet another way to stay connected, allowing them to power up their devices in a secure, sustainable way,” Walsh said in a statement.

Stations feature a 150-watt solar panel that towers over the structures. Users can walk up to a station, connect their smartphone or other mobile device to a cord inside one of multiple compartments, and lock it away. They can then feel free to explore the neighborhood, and stop into area bars or restaurants, before returning to a fully-charged phone.

“It provides an opportunity for people in an emergency situation to recharge their phones. I can leave my phone behind, and charge up, and then go out and about,” said Somerville spokesman Daniel DeMaina.

He said the lockers are secure, and users shouldn’t be afraid to leave devices behind.

Charging in the booths, called Model Zs, is free.