Carports and garages are both perfectly serviceable structures to protect your car. We’re talking about carports here, though, so we’re just going to mention that they’re cheap, easy to build, and have great air circulation.
There’s one more advantage to a German carport – it’s incredibly simple to roof it over with solar panels and let solar energy pay for the carport. Give it twenty years, and it’s paid for itself four or five times over. Germany’s legislation regarding renewable energy covers carports as well as actual buildings. Said legislation states that incentives for solar power are higher if the solar panels are attached to a structure than if they’re just free-standing, and a carport apparently counts as a structure. Another point for the carport.
Although incentives will decrease significantly for anything built after 2012, as of August 2011, solar power units on a roof generate an incentive of 28.74 cents (Euro, of course, which is about $0.41 American) per kilowatt hour, up to 30 KW. A free-standing system’s incentive is only 21.11 cents/kilowatt hour (about thirty cents American).
I live in the Midwest, though, where rain and/or snow falling sideways is not entirely uncommon, and I’m not sure a carport would be quite enough protection. On the other hand, solar panels on any kind of roof can only be a net positive.