The U.S. Environmental Protection Agency (EPA) is offering about $7 million in rebates to replace or retrofit older school buses.

This is the third rebate program under the Diesel Emission Reduction Act to fund cleaner school buses. The funding level for this year’s program is more than that of the past two editions combined — it was $3 million last year and $2 million in 2012.

Another change to the 2015 rebate program is the added option to implement retrofit technology — diesel oxidation catalysts plus closed crankcase ventilation systems, which reportedly reduce emissions by up to 25%.

As in previous editions of the program, fleets can also replace older buses with newer ones that meet the latest on-highway emission standards. EPA standards for new diesel engines make them more than 90% cleaner than older ones, according to the agency.

EPA will pay up to $3,000 for each retrofit system and between $15,000 and $25,000 per replacement bus, depending on the size. Applicants may request up to 10 buses for replacement and up to 10 buses for the retrofit option, per application. Fleets with more than 101 buses in operation may submit two applications.

Public and contracted school bus fleets are eligible to apply for the program. The rebates are for replacing school buses with engine model years 2006 or older, or for installing retrofit technology on school buses with engine model years 1994 to 2006.

EPA will accept applications from Sept. 28 to Oct. 30. For more information and to apply for the program, go here.