Energy Terminology

Ever wonder what kilowatt-hour really means? Or what the difference between polycrystalline and monocrystalline solar panels is? Well, you've found your answers here!

This page will certainly be a living document, expanded over time. Enjoy!

And be sure to check out the main pages of Home Power Saver where we discuss simple DIY projects and useful products that can reduce your energy usage.

[+] A-E
Alternating Current (AC) - Electric current typically used in long distance power transmission in which the current reverses direction at a set period. In the USA, most AC is 60 Hz, meaning it reverses 60 times per second.

Amorphous Semiconductor - A "thin film" semiconductor that is cheap, pliable, and easy to produce.  Amorphous 'panels' can be used in some applications where monocrystalline and polycrystalline panels can't, but are less efficient and were out more quickly.

Ampere – The measure of current in an electric circuit. Many home circuits are wired to support up to 15 or 20 amps of current at 120 volts.

Biodiesel - Diesel fuel made from vegetable oil or animal fat. Many diesel engines can be converted to operate on biodiesel

BTU - British Thermal Unit.  A common measure of the amount of heat created by burning a material.  Specifically, one BTU is the amount of heat required to raise one pound of water from 60 to 61 degrees Fahrenheit at one atmosphere pressure (760 mm Hg or 29.92 inches Hg).

Cellulose Insulation - Insulation based on plant fibers, sometimes in part made from recycled newsprint and other paper material, and usually treated with a fire retardant. Cellulose is an easy insulation to blow-in to attics to improve the R-value. In many applications, the choice is cellulose vs fiberglass.

CFL - Compact Fluorescent Light bulb, a long life, high efficiency bulb filled with gases that emit light when electrically charged.

CNG - Compressed Natural Gas, which is an alternative fuel which produces less carbon emissions than many fossil fuel alternatives. Many internal combustion engines can be converted to run on CNG.

Color Temperature - characteristic color spectrum of light. Often the color temperature of light is goes unnoticed until compared with a differing color temperature. For example, many incandescent lights have a yellower tinge, while some CFL's and most LEDs have a bluer tinge. Color temperature is measured in degrees Kelvin.

Compact Fluorescent - see CFL

Compressed Natural Gas - see CNG

Current – The flow of electrons through an electric circuit. Current is measured in amperes (amps).

Direct Current (DC) - An electric current that flows in one direction, typically used in electronic components and produced by solar panels. Compare to Alternating Current.

[+] F-J
Fiberglass Insulation - insulation made of glass fibers commonly used in commercial and residential insulation. Fiberglass insulation has some health concerns associated with it, but is thought to be safe with proper handling. In many applications, the choice is cellulose vs fiberglass.

Fluorescent Light - Compare with CFL. A Fluorescent light typically refers to a long tube shaped light often seen in office buildings, schools, and other ares requiring a wide dispersion of light.

Fuel Cell - an electrochemical device that converts a fuel source into electricity and water. Fuel cells are being researched to power cars and even homes and businesses.

Grid - refers to the electrical grid, which is a network connecting power sources (power plants) to customers using transmission lines.

Heat Pump - an appliance which draws heat from a warmer location and transfers it to a cooler location. Heat pumps are often efficient alternatives to traditional heating and air conditioning units, especially in certain climates.

HRU - Heat Recovery Unit. An HRU can be used on an Air Conditioner to channel heat to a hot water tank. HRUs have potential to increase your AC efficiency while simultaneously reducing your costs for heating water.

Incandescent Light - Incandescent light bulbs are traditional light bulbs that emit light by sending current through a filament until it glows brightly. Incandescent light is inefficient compared to LED and CFL lighting.

Inverter - Inverters convert DC current into AC current. An inverter is a necessary component in solar photovoltaic installations.

[+] K-O
Kelvin - measure of temperature used to quantify the color temperature of light. Most incandescent light is around 2600-2700 K, while LED lights may be 3000+ K.

Kilowatt - 1000 watts, based on the metric definition of kilo.

Kilowatt-Hour (KwH) - a common measure used by electric companies to determine electricity usage. A kilowatt hour represents 1000 watts used for 1 hour. For example, if 250 watts are being used, it would take 4 hours for 1 KwH to be consumed.

LED - Light Emitting Diode, and electronic component that emits light when energized. LED lighting is one of the most efficient lighting methods available, though it still is relatively expensive.

Lithium Ion - A battery technology that allows for high capacity and long life. Li-Ion technologies are often used in hybrid cars, computer and cell phone batteries, and other appliances.

Lumens - Lumens measure the amount of light produced. Lumens are an important specification when comparing dissimilar lighting technologies, such as LED, CFL, and Incandescent.

MERV - Minimum Efficiency Reporting Value. MERV is a rating scale that measures air filters, such as those used in residential and commercial heating and cooling systems. A higher number means better filtration, but usually at the expense of efficiency.

Monocrystalline Solar Panel - solar panels made from a single crystals of silicon. Monocrystalline panels are often more efficient, but more expensive, than polycrystalline panels.

MPP - maximum power point.  MPP represents the optimal current and voltage to obtain the most about of power on a solar PV system.

MPPT - maximum power point tracker.  MPPTs are power conditioners that operate solar PV arrays at its optimal MPP.

Net Metering - Mehotd by which the electic utility will purchase excess produced electricity at the wholesale rate. Net metering is common with residential solar PV installations.

Off-grid - Refers to generating enough power and reducing usage enough to allow you to disconnect from the electrical grid.

[+] P-T
Payback – amount of time for an investment to ‘pay for itself’. For example, $30 spent on CFL lightbulbs may result in 0.75 KwH power usage reduction per day. If you pay $0.12 per KwH, your payback would be 333 days.

Phantom Power – power that is consumed by electronic equipment even when the equipment is ‘turned off’. Phantom power is used by electronics to allow for faster power-on, or so that minimal functions can continue to run. Also known as Vampire Power.

Photovoltaic (PV) – refers to a means of generating electrical power using components (semiconductors) that can convert solar radiation into electricity (DC).

Polycrystalline Solar Panels - solar panels made from multiple crystals of silicon. Polycrystalline panels are often cheaper but less efficient than monocrystalline panels.

Power - the rate of doing work, measured in watts. Power is colloquially used interchangeably with electricity.

R-value - A measure of thermal resistance used to compare insulation qualities of materials and insulation levels in commercial and residential buildings. Local building codes vary, but most homes in the United States are recommended to have at least R-30 insulation in their attics.

Radiant Barrier - A reflective barrier (usually sheeting or paint-based) designed to reduce thermal radiation. Radiant barriers are often installed in attics, and are thought to reduce summer attic temperatures in some scenarios.

Return on Investment – see ROI

ROI - the amount of money earned over time from an investment of capital (money), typically expressed in a percentage. For example, a $30 investment in a SmartStrip may result in a $45 savings over 3 years, resulting in an ROI of 50%, or an annualized ROI of 16.7%. Compare to Payback.

SEER - Seasonal Energy Efficiency Rating. This is a common rating of central air conditioner system efficiency, with higher numbers meaning a more efficient system. However, do not assume a more efficient system can cool a larger space - the size of the space dictates the size of the unit in tons. As of January 2006 the USA requires all new units have a SEER of 13. Some super efficient units exceed 20 SEER.

Solar Power - Solar power refers to power generated from the sun's energy. A number of methods exist to convert solar energy into power, but the most common is based on Photovoltaic (PV) panels.

Surge - A surge, or power surge, is a short duration spike in voltage.

Surge Protector - A surge protector is a device which protects connected equipment from damage in the event of a surge. Surge protectors are often included in power strips.

Tankless Water Heater - A tankless water heater is a special demand-based water heater that operates using a heat exchanger. Tankless water heaters are generally more efficient than traditional tank heaters since they only heat water when there is a need. Tankless heaters can be gas, electric, or propane powered.

[+] U-Z
Watt – standard measure of power, derived from multiplying volts by amps (Ohm’s Law)

Vampire Power - power that is consumed by electronic equipment even when the equipment is ‘turned off’. Phantom power is used by electronics to allow for faster power-on, or so that minimal functions can continue to run. Also known as Phantom Power.

Volt – Unit of measure of electric potential. A volt can be thought of as a measure of force or pressure when considering electricity as compared to a plumbing system. In the US, most Alternating Current (AC) circuits operate around 120 volts.