A (10) | B (1) | C (9) | D (15) | E (8) | F (3) | G (5) | H (3) | I (8) | K (2) | L (4) | M (11) | N (6) | O (3) | P (16) | R (6) | S (10) | T (5) | U (1) | W (6) | Z (1)
Term Definition
Independent Power Producer (IPP)

An electricity generator that sells power but is not owned by a utility.

Independent System Operator (ISO)

An independent third party responsible for maintaining secure and economic operation of an open access transmission system on a regional basis. An ISO provides availability and transmission pricing services to all users of the transmission grid.

Installation Costs

All the expenses required to construct and get a turbine up and running including but not limited to foundation construction, laying of electrical wire, crane, labor, and other associated costs.


The process of connecting an electrical generator to the electrical power grid or the physical location of the connection of an electrical generator to the electrical power grid.

Interconnection Agreement

A legally binding document that defines the technical and contractual terms under which a generator can interconnect and deliver energy to a transmission operating utility’s system.

Internal Rate of Return (IRR)

A financial calculation that compares the present value of a project’s expected revenues with the present value of its expected costs. The IRR calculation is used to determine the discount rate at which the two values are equal. By doing this calculation, investors are able to see the project’s expected rate of return. The IRR will be a number where revenue exceeds the costs of financing the project. This means a surplus will remain after paying for the capital, and the investors will benefit from the investment. If the IRR is less than the cost of capital, the investors are not likely to participate in the project.

Investor-Owned Utility (IOU)

A utility owned by private investors as opposed to one owned by a public trust or agency; a commercial, for-profit utility as opposed to a co-op or municipal utility.

IRS Private Letter Rulings

A notice from the IRS that makes a ruling on how a particular portion of the tax code applies in a specific instance for an individual or business. Many community wind projects have asked the IRS for rulings on the ability of the project’s business structure to take advantage of the production tax credit (and other tax advantages) in a way that is within the law. Private letter rulings from the IRS only apply to the specific project the ruling is addressed to.