TAMPA Supply could soon catch up with demand for Tampa's free Downtowner shuttle service thanks to the addition of two new all-electric Chevrolet Bolts Wednesday.The on-demand pickup service will now have eight vehicles on the road at all times instead of six to respond to pickup requests that riders place via an app."It's been overwhelmingly popular," said Karen Kress, director of transportation and planning for the Tampa Downtown Partnership. She led the initiative to launch the free electric shuttles.The Downtowner hit the 100,000-rider mark less than seven months after launching last October, and currently about 500 people a day use the service.Wait times average 26 minutes, with the heaviest demand coming during morning and evening rush hours and at lunch. One of the program's most popular pickup and drop-off locations is the Marion Transit Center, and a good portion of the demand is driven by commuters looking to cover the first and last miles of their trips between home and work.Including the lease, the drivers, insurance, maintenance and other expenses, each Bolt will cost about $100,000 a year to put on the road. The $1 million-per-year program is paid for with city redevelopment property tax revenue, plus state and federal funds and contributions from the nonprofit Partnership and downtown hotels, office towers and developers.The addition of the Bolts is expected to reduce wait times, support the growth in demand and — blissfully — provide some air-conditioned rides. The Downtowner's original vehicles, a five-passenger mini-shuttle known as a GEM, have their own charm, but their lack of air conditioning means that they often roll through downtown with windows open.Another key difference between the Bolts and GEMs is the Bolts can go more than 200 miles on a single charge, allowing them to stay on the road all day.In contrast, the 12 GEMs in the Downtowner's fleet are limited to around 60 miles per charge, meaning that half of them are on the road and half are on a power cord at any one time."The Chevy Bolt's range allows us to move more people with less resources," Downtowner chief operating officer Travis Gleason said.Still, riders won't be able to request a Bolt versus a GEM. The app used to hail rides dispatches them based on what will provide the shortest wait time. There's no way to ask for a specific vehicle or driver.The Downtowner runs 6 a.m. to 11 p.m. weekdays and 11 a.m. to 11 p.m. weekends in the central business district, the area around the University of Tampa, the Channel District and the Tampa River Arts District, which includes Curtis Hixon Waterfront Park, the Tampa Museum of Art and the David A. Straz Jr. Center for the Performing Arts, plus the nongated northern end of Harbour Island."We would like to expand the program further because the demand is so high," Kress said. But the program would need to get local companies to advertise on vehicles, something made possible now that the Hillsborough County Public Transportation Commission, which had rules blocking such branding, is being dissolved. "We think that there's demand enough for two more Bolts,'' Kress said, "but that will be dependent on raising the funds to support them."