A closed loop or path in which current can flow.


It is the flow of electric charge measured in Amps.

Electromagnetic Radiation

A form of energy that propagates through space as oscillating magnetic and electric fields. It travels in the form of waves. The spectrum is made up of radio waves, microwaves, infrared, visible light, UV radiation, X Rays, Gamma Rays.


A form of energy that comes from the existence and movement of charged particles- electrons and protons.


The capacity of a system to perform work or undergo a physical transformation. It cannot be created or destroyed but it can be converted to one form or another.

Fill Factor

The ratio of the maximum power output of a solar cell to the product of its open circuit voltage and short circuit current. A higher fill factor means a more efficient solar cell as a larger portion of the absorbed sunlight is being absorbed and being converted into usable electrical power.


An electronic device that converts DC to AC. DC is current that flows in one direction and AC is current that periodically changes direction.


Made to isolate certain sections of the PV system for safety and maintenance. A DC isolator cuts off DC power coming from the solar panels into the inverter. AC isolator cuts off AC power being supplied to grid or into a house or building. Can also be called a disconnect switch or circuit breaker.


The energy transferred when one amp of current flows through an electrical potential difference of one volt for one second.

Kilowatt Peak (kWp)

The maximum output a solar PV system can achieve under optimal conditions. Optimal conditions mean solar irradiance of 1kw per square meter and a temperature of 25 degrees celsius.


A kilowatt hour is a unit of energy commonly used to measure and quantify electrical energy consumption. It represents the amount of energy consumed when a power load of 1kw is used continually for one hour. For example:

  • A 1KW appliance (or 1000 watts) running for one hour would use 1kWh
  • A 0.5 KW appliance (500 watt) running for two hours would use 1kWh

Parallel Circuit

Components are connected side to side with each offering a separate path for current to flow. Current divides among those components and if one fails or is less/more, the current can take other paths and the circuit continues to function.


This is the rate at which work is done or the rate at which energy is transferred or converted per unit time. Power quantifies how quickly work can be performed or energy can be transformed from one form to another.

Series Circuit

Components are connected end to end in a single path so current has to go through each component in turn. If one component fails, the current stops and the circuit fails.

Solar Irradiance

The power per unit area received from the sun in the form of electromagnetic radiation. It is typically measured in watts per square metre.


Think of the sun as a giant ball of hot gases where hydrogen atoms (isotopes) are being slammed into one another and creating helium. This process, called fusion, creates loads of energy in the form of light and heat that radiates down to earth.


Used for very large amounts of electricity. It is equal to 1 billion kilowatt hours


The force that drives electric charge (current) through a medium. It is measured in Volts.