Lime Bikes is now only renting electric-powered models ebikes, which use a small motor to give riders a boost as they accelerate or go up a hill, the Boston Globe reports.

But the switch will come with one big drawback for riders: the electric bikes are more expensive. According to the company’s app, they cost $1 at the start and 15 cents a minute, compared to $1 for 30 minutes on a traditional bike.

 

Eric Bourassa, transportation director of the Metropolitan Area Planning Council, a regional agency that organized the bike-rental system, said the switch to an electric-only fleet raised concerns among activists and local officials that the increased cost will be too much for some low-income users.