The bill, which has now been sent for approval by President Obama, was passed by a 76-16 vote late last night. The House of Representatives approved the bill on 3 December.
An extension allows US projects that began construction activities in 2014 to apply for the credit. It gives producers of wind power a $0.023/kWh incentive.
A one year extension casts doubt on the willingness or ability of Congress to revisit the PTC in 2015, said Luke Lewandowski from Make Consulting.
"This results in long-term doubt that will undoubtedly have severe consequences on the domestic supply chain," he said.
The Senate Finance Committee approved a two-year extension to the PTC in April, as part of a package of tax measures. Chairman of the committee, democrat Ron Wyden, voted against the bill to try and force a two-year extension.