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  • Writer's pictureKerry Lipp

Solar/Electrical Glossary

Updated: Jan 30, 2019

AC - Alternating Current

AHJ - Authority having jurisdiction. Usually the code enforcement officer or electrical inspector.

Alternating Current - A form of electricity that reverses polarity multiple times per second, typically 60Hz in the U.S. and 50Hz elsewhere. AC voltage can be easily transformed to higher voltages which allows it to be transmitted over long distances without significant losses. See Direct Current.

Amperes - See Current

Amp Hours or Ah - Amps x hours. Unit typically used to describe battery capacity. For example if a battery is rated at 100 Ah, it could deliver 1A for 100 hours or 5A for 20 hours. Battery capacity is dependent on rate of discharge. Smaller battery capacity is described in milliamp hours (mAh) and one Ah = 1000 mAh.

Amps - The rate of electrical flow. The higher the amps, the more electrons are flowing per second. 1A = one coulomb per second.

Array - Any number of PV modules grouped together and having the same tilt and azimuth.

Azimuth - The compass angle toward which an array faces. For example: 90 degrees azimuth is the same as due east and 180 degrees azimuth is true south. An azimuth of 180 degrees will provide the most amount of sunlight energy on average. See Tilt.

Battery - Typically a device which stores electrical energy in a chemical form. Common chemistries include flooded lead-acid (FLA), absorbed glass mat (AGM), gel cell, and Lithium.

Bond, Bonded - Connected for electrical continuity.

Charge Controller - A device that regulates voltage and current flow. Used to properly charge deep cycle batteries. Prevents over-charging and under-charging of batteries.

Conservation - Using less. Conservation is a form of efficiency.

Coulomb - Unit of electrical charge. One coulomb = 6,241,500,000,000,000,000 electrons.

Current - See Amps

DC - Direct Current

Direct Current - A form of electricity that does not change polarity. Direct Current, or DC, is the type of electricity produced by solar modules

DOD - Depth Of Discharge. Usually expressed as a percentage. Used to describe the amount of battery capacity that has been removed. See SOC

Efficiency - Using less to do the same. Often defined as a ratio of the amount of useful work per energy input.

Energy - Power x time. The amount of power that something uses times the amount of time, in hours, that it is turned on. The unit of energy is the watt-hour or killowatt-hour. See Power, Killowatt-hour, Watt-hour.

Frequency - Measured in Hz (Hertz) or cycles per second. In electrical context, the number of times per second that polarity changes between phases. In the US the standard is 60Hz.

Grid-Tied - Connected directly to the utility's power lines, as in grid-tied PV system, or grid-tied inverter.

Ground, Grounded - Physical connection to the earth.

Incentives - Rewards or benefits, usually financial. Examples include rebates, tax credits, and low interest loans.

Inverter - Electrical equipment which converts DC power to AC power.

Irradiance - Light intensity. Measured in Watts per square meter. Module standard test conditions use an irradiance of 1000 Watts per square meter to measure power output. 1000 Watts per square meter is approximately the light intensity of a bright sunny day.

kWh - Kilowatt-hour

Killowatt-hour - The standard unit of energy. One kWh = 1000 Wh. See Watt-hours.

NEC - National Electrical Code

Net metering/Net metered - A policy incentive for grid-tied solar producing utility customers where excess production is credited, kWh for kWh, and can be used later on.

NYSERDA - New York State Energy Research and Development Authority.

OCPD - Over-current protection device. A thermally or magnetically operated device that prevents the overheating of electrical wires caused by too much current. Typically a circuit breaker or fuse.

Ohms - Unit of resistance.

Panel - Common or slang term for a solar module. Also can refer to a main service panel or breaker panel.

Photovoltaic - The conversion of light into electricity.

Power - See Watts.

PV - See Photovoltaic.

Renewable - As in energy, a natural resource that is not finite. Examples include solar, wind, and hydro.

Resistance - The ability of an object (usually a wire, heater element, or resistor) to pass current. Measured in Ohms. A larger wire has less resistance than a smaller one and can carry more current without overheating.

SOC - State Of Charge. Usually expressed as a percentage. Used to describe the amount of battery capacity that is remaining. See DOD.

Solar - relating to the sun or sunlight.

Solar Module - A component of a PV system that converts light into electricity. Rated to produce a specific wattage under Standard Test Conditions (STC).

Solar Panel - Same as Solar Module.

Standard Test Conditions - 1000 Watts per square meter irradiance at 25 degrees Celsius

State of Charge - See SOC.

Sustainable - A way of using natural resources without their depletion.

Tilt - The angle from the horizon that an array faces. See Azimuth.

Volts or Voltage - Unit of difference in electrical potential. Often described as electrical pressure.

Watts - Unit of power. Used to describe how much electricity an appliance is using instantaneously. Watts = Volts x Amps. See Watt Hours.

Watt-hours - Watts times hours, A unit of energy. Used to describe how much electricity an appliance uses over time. For example, if you turn on a 40 Watt light bulb for two hours, you will have used 80 Watt hours.

Wh - See Watt Hours

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