Alternative Energy Certificate. A digital certificate certifying production of 1,000 kilowatt-hours (kWh), or 1 megawatt-hours (MWh) of clean solar electricity. These are tradable, selling on an open market, with prices varying depending on the state in which you live.

Alternating Current (AC)
A type of electrical current, the direction of which is reversed at regular intervals or cycles. In the United States, the standard is 120 reversals or 60 cycles per second. Electricity transmission networks use AC because voltage can be controlled with relative ease.

Direct Current (DC)
A type of electricity transmission and distribution by which electricity flows in one direction through the conductor, usually relatively low voltage and high current. To be used for typical 120 volt or 220 volt household appliances, DC must be converted to alternating current, which is done by an inverter.

Federal Investment Tax Credit (FITC)
Established by the federal Energy Policy Act of 2005 and enhanced in February 2009 by The American Recovery and Reinvestment Act of 2009, allows businesses and homeowners a tax credit equal to 30% of the total installed cost of a solar electric or thermal system. The credit can be carried forward until with no maximum credit.

A solar electric or thermal system which is connected to a utility grid, allowing it to send excess energy into the grid. Grid-tied systems are desirable whenever utility lines are available, as it allows you to reduce costs by selling power back to the grid and pulling power from it when needed.

Heat Exchanger
Found in closed loop Solar Hot Water systems, they allow the transfer of heat from one fluid to another without the two mixing.

A device that converts direct current electricity to alternating current either for stand-alone systems or to supply power to an electricity grid.

Kilowatt (kW)
A standard unit of electrical power equal to 1000 watts,

Kilowatt-Hour (kWh)
1,000 watts acting over a period of 1 hour.

Net metering
A billing arrangement by which you as a generator of electricity receive utility bill credit for electricity generated but not used on site. The unconsumed or excess power is sent back to the utility grid and credited to your next bill at the full retail rate.

Photovoltaic (PV)
The direct conversion of light into electricity.

Photovoltaic Array
An interconnected system of PV  modules that function as a single electricity-producing unit.

Photovoltaic Module
A discrete assembly of photovoltaic cells which make up a PV system. These are generally 3 ft x 5 ft and weigh 40 pounds. PV  modules are mounted on a roof, pole, or the ground and convert the sunís energy into DC power.

Solar Thermal Collectors
A solar collector gathers and stores the sunís energy via a network of pipes through which water or anti-freeze is heated. Flat plate collectors are the most common type; they consist of copper tubes fitted to a flat absorber plate. Evacuated tube collectors are more efficient, working best in cold, cloudy climates.

Solar Renewable Energy Certificate. See AEC.