Though wind energy is now more affordable, more available, and pollution-free, it does have some drawbacks. Wind power suffers from the same lack of energy density as direct solar radiation. The fact that it is a "very diffuse source" means that "large numbers of wind generators (and thus large land areas) are required to produce useful amounts of heat or electricity." But wind turbines cannot be erected everywhere simply because many places are not windy enough for suitable power generation. When an appropriate place is found, building and maintaining a wind farm can be costly. It "is a highly capital-intensive technology." If the interest rates charged for manufacturing equipment and constructing a plant are high, then a consumer will have to pay more for that energy. "One study found that if wind plants were financed on the same terms as gas plants, their cost would drop by nearly 40%." Fortunately, the more facilities built, the cheaper wind energy is.