Solar Power Terminology

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These are common terms, descriptions, and definitions you should be aware of when shopping for solar power. Understanding this terminology before you start talking with solar power installers will help you communicate with the contractors. You will likely see these terms in their proposals and marketing material.

• Alternating Current (AC) - The type of electrical power supplied by utilities. This form of electricity has a current that reverses direction at regular intervals. This is the most common type of household electricity. In the USA and Canada, the direction of flow is reversed 120 times a second, resulting in 60 complete cycles per second.
• Angle of Incidence - the angle between the surface of an object and the direction of the sunshine. Solar panels produce the most power when the surface of the solar panel is exactly perpendicular to the direction of sunlight. On some solar power farms, motorized trackers keep each cell pointed in the optimum direction as the sun moves across the sky. More recent experience shows it is better not to rely on mechanical devices to move the solar panels, as they wear out, but invest that money in more solar panels instead.
• Array - A group of solar panels wired together.
• Balance of system (BOS) - all the components and costs other than the solar panels. It includes design costs, site preparation, system installation, support structures, operation and maintenance costs, etc.
• Direct Current (DC) - The type of electricity generated by solar panels. The current flows only in a single direction. The most common form of electricity used in cars, boats and RVs. Small devices such as torches or radios use DC current, usually powered by batteries.
• ESA - the Electrical Safety Authroity, which is the governing body who inspects electrical installations in Ontario, Canada.
• Grid - When used in reference to utility power, it refers to a system of electrical transmission and distribution lines.
• Grid-connected Solar Power - Grid-connected solar power, also known as on-grid or grid-tied solar power, generates electricity for the electric utility grid.
• Inverter - An inverter converts the power generated from solar panels from direct current (DC) to alternating current (AC) for use in the home or for export to the grid. An inverter can also be used to convert DC power from storage batteries to AC power for use in the home or business. Also see Micro Inverter.
• Irradiance - the amount of solar energy that strikes a surface during a specific time period. Measured in kilowatts.
• Kilowatt (kW) - One thousand watts of electrical power. Ten 100-watt light bulbs use one Kilowatt of electrical power.
• Kilowatt-hour (kWh) - One thousand watts of electrical power used or generated in one hour. The kWh is a unit of energy. Most electrical meters measure kWh for billing purposes. A typical Canadian household uses about 10,000 kWh per year.
• Lightning Arrestor - a type of fuse used to protect the solar power system in the event of a lightning strike.
• Micro Inverter - this is a small inverter (see Inverter) that mounts to the back of each solar panel instead of having one large inverter. While it works better when partial shading is a concern, it also introduces multiple points of potential failure, which is a concern for roof mounted solar panels.
• Net metering - A practice used in conjunction with a solar electric system where your electric meter tracks your net power usage, spinning forward when you use electricity from the utility, and spinning backward when your system is generating more electricity than you need.
• Off Grid Solar - An array of solar panels that support a home is not connected to a utility power distribution grid.
• Orientation - A term used to describe the direction that a solar module faces. The two components of orientation are the tilt angle (the angle the panel makes from the horizontal) and the aspect angle (the direction the panel faces such as south or south west).
• Parallel Wiring - A group of electrical devices, such as PV modules, wired together to increase ampacity, while voltage remains constant.
• Passive Solar Home - A home that captures the heat from the sun shining through windows, as opposed to active solar, such as photovoltaic (PV).
• Photovoltaic (PV) - the direct conversion of light into electricity. Photo means "light", voltaic means "electric".
• PV - Abbreviation for photovoltaic.
• Series Wiring - A group of electrical devices, such as PV modules, wired together to increase voltage, while ampacity remains constant.
• Solar Energy - radiant energy emitted by the sun.
• Solar Panel - a panel designed to absorb the sun's rays as a source of energy for generating electricity or heating.
• Solar Panel Efficiency - the percent of electrical energy that a solar panel produces (under optimal conditions) as compared to the total amount of energy from the sun falling on the solar panel. Typical solar panel efficiency is currently between 12% and 18%, although this value is improving over time. See solar panel efficiency for an example and more details
• Solar Power - power obtained by harnessing the energy of the sun's rays.
• Tilt Angle - The angle of inclination of a module measured from the horizontal.
• Watt (W) - A unit of power, or the amount of work done in a period of time. One ampere of current flowing at a potential of one volt produces one watt of power. A typical household light bulb uses 60 watts of power. A person climbing a flight of stairs uses 200 watts of power.