It’s pretty impressive for a solar-powered car to average 60 mph over a long stretch of 1,800 miles, even if some of the roads in the Australian Outback lack speed limits.

That’s the top speed of any car in the World Solar Challenge, a race across Australia now having its 13th outing. “To put that into perspective, that’s not easy to do in a conventional car,” says event director Chris Selwood.

Speed is just one of the ways the cars, which rely on solar panels for 90% of their energy needs, have improved over time.

The rules for the contest have tightened considerably, says all-around race mastermind Selwood. In the early days, the cars carried as much as 140 kilograms of a lead battery. Now, some of cars get by with just 18 kilograms of lithium polymer. That makes them smaller and lighter and more efficient. Plus, all the cars need to be four-wheeled these days, which makes them more stable.

Indeed, several cars look more and more like “conventional cars”–more compact, certainly. Look at the Solar Riser from the HS Bochum SolarCar-Team, in Germany. It looks like a sports car.

The student team behind Eindhoven University’s Stella Lux describes it as a “family vehicle.” The car is remarkable for being energy positive–it captures power when its owners aren’t using it during the day.

“In the urban commuting cycle in their country [the Netherlands], the car collects more energy than it uses in that community. It provides a contribution to their household electricity,” Selwood says.