Solar Energy - Glossary


The term capacity refers to the maximum power that a machine, such as an electrical generator, or system, such as a transmission line, can safely produce or handle at any given time.

Generation (Electricity)

The process of producing electric energy from other forms of energy; also, the amount of electric energy produced.

Green Energy

A popular term for energy produced from renewable energy resources or from clean (low-emitting) energy sources.


The term grid refers to the layout of an electrical distribution system.

Kilowatt (kW)

The kilowatt is a unit for measuring power and is equal to 1,000 watts.

Kilowatt-hour (kwh)

Energy generation or use is expressed in units of time, most commonly, the hour. For example, one watt hour is the amount of energy expended by a one watt load (e.g. a light bulb) for the duration of one hour. A kilowatt-hour is equal to 1,000 watt hours. A 100 watt light bulb burning for 10 hours would be the equivalent of one kilowatt-hour. The average household has a demand for energy that is equal to 10,000 kilowatt hours per year.

Megawatt (MW)

A megawatt is equal to 1,000 kilowatts or one million watts.

Megawatt-hout (mwh)

Equal to 1,000 kilowatt hours or 1 million watt hours.


The term off-taker refers to the recipient of the end-product of a project. The off-taker in many cases is the utility company that purchases the energy generated.

Photovoltaics (PV)

Photovoltaics is a method of generating electrical power by converting solar radiation into direct current electricity using semiconductors that exhibit the photovoltaic effect. Photovoltaic power generation employs solar panels composed of a number of solar cells containing a photovoltaic material.

Power Purchase Agreement (PPA)

The Power Purchase Agreement is a supply contract between the energy generating company (i.e. Western Wind) and a large utility company, or other such customer, for the purchase of a set amount of energy.

Production Tax Credit

In the United States, a tax credit is granted to companies that generate energy from renewable sources such as wind power. The federal government currently offers a tax credit of 2.0 cents per kilowatt-hour for the first ten years of a renewable energy facility's operation.

Renewable Portfolio Standard (RPS)

A Renewable Portfolio Standard is a regulatory policy in the United States that requires the increased production of renewable energy sources. It places an obligation on electricity supply companies to produce a specified fraction of their electricity from renewable energy sources. Certified renewable energy generators earn certificates for every unit of electricity they produce and can sell these, along with their electricity, to supply companies. Supply companies then pass the certificates to a regulatory body to demonstrate their compliance with their regulatory obligations.

Renewable Electricity Standard (RES)

A Renewable Electricity Standard outlines the required percentage of energy that an electricity supplier must generate through a renewable energy source. Renewable Portfolio Standards frequently ease that requirement through the tradable certificates.

Renewable Energy Resource

An energy resource that is regenerative or virtually inexhaustible. Typical examples are wind, solar, geothermal and water power.

Solar Panel

A solar panel (also solar module, photovoltaic module or photovoltaic panel) is a packaged, connected assembly of photovoltaic cells. The solar panel can be used as a component of a larger photovoltaic system to generate and supply electricity in commercial and residential applications. Each panel is rated by its DC output power under standard test conditions, and typically ranges from 100 to 320 watts. The efficiency of a panel determines the area of a panel given the same rated output - an 8% efficient 230 watt panel will have twice the area of a 16% efficient 230 watt panel. Because a single solar panel can produce only a limited amount of power, most installations contain multiple panels. A photovoltaic system typically includes an array of solar panels, an inverter, and sometimes a battery and or solar tracker and interconnection wiring.

Transmission System (Electric)

The transmission system is the grid which allows the delivery of electricity to consumers or utility companies (usually in bulk). The system is comprised of an interconnected group of electric transmission lines.