Boston’s parks are getting a string of benches with built-in cellphone chargers. But it’s unclear at best whether it’s a financially viable proposition.

The Soofa, described as an urban hub, has a built-in solar panel which provides the power for two USB ports for charging. (You need to bring your own charging cable.) Officials say charging time should be similar to what you’d experience from a normal power outlet.

Real-world testing by Boston.com suggests that’s about right. That means that it’s certainly not viable for most people to carry out a full charge, but a 10 minute sit-down should be enough to get a useful boost when you’re on the move.

The benches also have a connection to a 4G LTE network, but this isn’t accessible to the public at the moment. Instead the connection is used for uploading information on use of the chargers, along with data from noise and pollution sensors.

The electronics is housed in a concrete box that’s sealed with security screws that can only be opened with a specific tool, reducing the chances of anyone tampering with the USB ports. One downside is that as well as taking up about 30 percent of the seating space, the box covers its full depth and means the benches are backless, reducing their comfort levels.

The organization behind the benches, Changing Environments, is still a bit hazy on the economics. The batch being installed in Boston is being funded by sponsorship by Cisco. The organization has also talked about having some sort of installation and subscription fee (presumably paid by local authorities or landowners) or selling data on local footfall collected by motion sensors.

Realistically then, it may be that Soofa is more of an awareness tool for solar energy than a sustainable business model.