Study: Parking Minimums Cost Seattle Renters $246 a Month

Sightline found that in its survey of 23 recently built apartment buildings, 37 percent of spaces were empty at night, the time of day when you'd expect parking to be in highest demand. In four developments, there were more than twice as many parking spaces as parked cars (meaning more than half the spaces were empty). On average, the buildings in the survey had 20 percent more apartments than cars, meaning that if car-owning renters averaged one car per apartment (a conservative estimate if you take seriously parking advocates' claim that many small-apartment dwellers have multiple cars), only 80 percent of renters owned cars.

And here's the problem with all that extra, unused parking: Everybody, including people who don't own a car, pays for it. "Free" parking adds about 15 percent to the cost of renting an apartment -- in Seattle, about $246 a month.

Regardless of the reasons for the parking glut, the fact that developers provide abundant (and often unneeded) on-site parking significantly increases the supply-side costs of building new multifamily rental housing. Economic theory posits that higher supply-side costs reduce the amount of new housing that is built.