Tex. Tax Code § 171.107

(a) In this section, "solar energy device" means a system or series of mechanisms designed primarily to provide heating or cooling or to produce electrical or mechanical power by collecting and transferring solar-generated energy. The term includes a mechanical or chemical device that has the ability to store solar-generated energy for use in heating or cooling or in the production of power.

(b) A taxable entity may deduct from its apportioned margin 10 percent of the amortized cost of a solar energy device if:

(1) the device is acquired by the taxable entity for heating or cooling or for the production of power;

(2) the device is used in this state by the taxable entity; and

(3) the cost of the device is amortized in accordance with Subsection (c).

(c) The amortization of the cost of a solar energy device must:

(1) be for a period of at least 60 months;

(2) provide for equal monthly amounts or conform to federal depreciation schedules;

(3) begin on the month in which the device is placed in service in this state; and

(4) cover only a period in which the device is in use in this state.

(d) A taxable entity that makes a deduction under this section shall file with the comptroller an amortization schedule showing the period in which a deduction is to be made. On the request of the comptroller, the taxable entity shall file with the comptroller proof of the cost of the solar energy device or proof of the device's operation in this state.