Aluminum alloys used for electrical conductors are only approximately 61% as conductive as copper of the same cross-section, but aluminum's density is 30.5% that of copper. Accordingly, one pound of aluminum has the same current carrying capacity as two pounds of copper. Since copper costs about three times as much as aluminum by weight (roughly USD $3/lb vs. USD $1/lb ), aluminum wires are one-sixth the cost of copper wire of the same conductivity. The lower weight of aluminum wires in particular makes these electrical conductors well suited for use in power distribution systems by electrical utilities, as supporting towers or structures only need to support half the weight of wires to carry the same current.