QUALIFYING VEHICLES.

(a) A vehicle is a qualifying vehicle that may be considered for a grant under the program if during the eligibility period established by the commission the entity:

(1) purchased, leased, or otherwise commercially financed the vehicle as an on-road heavy-duty or medium-duty motor vehicle that:

(A) is a new natural gas vehicle or, subject to Subsection (c), a used natural gas vehicle;

(B) is certified to the appropriate current federal emissions standards as determined by the commission; and

(C) replaces an on-road heavy-duty or medium-duty motor vehicle of the same weight classification and use; or

(2) repowered the on-road motor vehicle to a natural gas vehicle powered by a natural gas engine that is certified to the appropriate current federal emissions standards as determined by the commission.

(b) A heavy-duty or medium-duty motor vehicle is not a qualifying vehicle if the vehicle or the natural gas engine powering the vehicle:

(1) has been awarded a grant under this chapter for a previous reporting period; or

(2) has received a similar grant or tax credit in another jurisdiction if that grant or tax credit program is relied on for credit in the state implementation plan.

(c) A used natural gas vehicle that is proposed to replace an on-road heavy-duty or medium-duty motor vehicle must be of model year 2017 or later, provided that the model year may not be more than six years older than the current model year at the time of the submission of the grant application.