Brought to you in part by

Long Island Solar Roofs Initiative

Glossary

Alternating Current (AC) - The flow of electricity that constantly changes direction between positive and negative sides. Almost all power produced by electric utilities in the United States moves in current that shifts direction at a rate of 60 times per second.

Ampere (Amp) - The unit of measure that indicates how much electricity flows through a conductor. It is like using cubic feet per second to measure the flow of water. For example, a 1,200-watt, 120-volt hair dryer pulls 10 amperes of electric current (amps = watts/volts).

Average Demand - The energy demand for a given location over a period of time. For example, the number of kilowatt-hours used in a 24-hour period, divided by 24 hours, tells the average demand for that location in that time.

Avoided Cost - The amount of money an electric utility would need to spend for the next increment of electric generation to produce or purchase.

Battery - Batteries are often sold with a solar electric system. The primary purpose is to store the electricity not immediately used, which could be used at some later time.

Circuit - One or more conductors through which electricity flows.

Converter - An electrical apparatus that changes the quantity or quality of electrical energy.

Customer Load - The amount of power your site uses. Load may be expressed in kilowatts (capacity) or kilowatt-hours (energy). A site's peak kilowatts generally refers to when electric demand requirements are highest.

Demand - The level at which electricity is delivered to end-users at a given point in time. Electric demand in measured in kilowatts.

Direct Current (DC)- The flow of electricity that flows continuously in one direction. Frequency - The number of cycles through which an alternating current moves in each second. Standard electric utility frequency in the United States is 60 cycles per second, or 60 Hertz (Hz).

Grid - The electricity transmission and distribution system that links power plants to customers through high-power transmission line service.

Hertz - The unit of electromagnetic frequency that is equal to one cycle per second.

Interconnection - The linkage of transmission lines between two utilities, or between a utility and an end-user, enabling power to be moved in either direction.

Kilowatt (kW) - 1,000 watts. A unit of measure of the amount of electricity needed to operate given equipment. For example, a one kW system is enough power to illuminate 10 light bulbs at 100 watts each. (volts x amps = watts)

Kilowatt-hour (kWh) - The amount of kW produced over a period of time, or one kilowatt of electricity supplied for one hour. For example, a one kW system, if operating at full capacity for 5 hours will produce (or use) 5 kWh of electricity.

Megawatt - One thousand kilowatts or one million watts. One megawatt is enough to power 1,000 average California homes. Meter - A device that measures levels and volumes of customer's electricity use.

Mounting Equipment - Equipment/apparatus used to fasten solar (PV) modules to the roof. Peak Load - The highest electrical demand within a particular period of time.

Net Metering - In the fall of 1998, New York State Governor George Pataki signed the Solar Choice Act, which requires all the investor owned electric utilities in NYS to allow residential customers to interconnect PV (solar electric) systems to the utility's distribution systems. These grid-connected PV systems allow residential customers to run their electric meters backwards, offsetting their normal utility bill. Other than the renewable energy system, no special equipment is needed.

Photovoltaic Cell or Module (PV) - A device that produces an electric reaction to light, thereby producing electricity.

Solar Energy - Heat and light radiated from the sun.

Solar Thermal - The process of concentrating sunlight to create high temperatures that are needed to heat fluids, like water (solar hot water) or to vaporize fluid to drive a turbine for electric power generation.

Storage - Storage refers to saving surplus electricity produced by a photovoltaic (PV) system. Generally, batteries are used as storage devices.

Tracking Equipment - Structure that houses PV modules and that can automatically follow the sun across the sky throughout the day to maximize output.

Utility Grid - The interconnection of electricity generation plants through the transmission and distribution lines to customers. The grid also refers to the interconnection of utilities through the electric transmission and distribution systems.

Volt (V) - The amount of force required to drive a steady current of one ampere through a resistance of one ohm. Electrical systems of most homes and offices use 120 volts. (volts - watts/amps) (volts = amperes x resistance)

Watt (W) - Electric measurement of power at one point in time, as capacity or demand. For example, light bulbs are classified by wattage. (1,000 watts = 1 kilowatt).