It's important to know the terminology of the trade before you begin your lighting project. Understanding what you need and being able to match it with lighting features and descriptions will make sure your project turns out the way you wanted it to.
This list, while not exhaustive, is a great way to get started on understanding the technical aspects of picking the right light for you.
VOLTAGE (V): A measure of electric potential difference, or electromotive force, in an electrical circuit. If light was water coming out of a hose, you can think of voltage being the pressure that pushes the water out. The standard voltage in North America is 120V, but based on your power needs, you can get fixtures with a different wattage.
WATTAGE (W): The amount of power consumed by a light source. In the hose analogy, wattage would be the amount of work the water would be able to do (in turning a water wheel, for example). A higher wattage does not necessarily mean that your fixture will be brighter. Wattage comparisons vary depending on the type of light source you choose. To really compare the light produced, it is more useful to consider the fixture’s lumen output.
KILOWATT-HOUR (kWh): This is a measure of how much energy is used over time, specifically the consistent usage of 1kW (1000W) in one hour. Ten 100W bulbs, running simultaneously for an hour, would use 1kWh worth of energy. This is important because most electricity bills are measured in $/kWh – meaning lights with a lower wattage will cost you less every time you have to pay your utility bill.
LUMEN: A measure of the visible light emitted by a light source. Brightness, technically known as luminance, is a measure of how bright a surface will appear to a viewer when illuminated.
EFFICACY: Commonly referred to as efficiency, it is a measure of how effectively a light source converts electrical energy to visible light. It's measured in lumens per watt (LPW). For reference, an average LED efficiency level is 100 lumens/watt.
|Source: Peak Busters|
LIFE & LONGEVITY: How long a bulb will last until it needs to be replaced. As a point of comparison, the standard lifespan of an LED today is 100,000 hours – or 22 years of 12 hour-a-day usage.
COLOUR TEMPERATURE (K): A description of colour of light emitted by a light source. This is measured in degrees Kelvin (K), because as colour temperature changes, so does the light’s appearance. This may get a little confusing, but lower temperatures are associated with the “warmer”, orange light colour, while higher temperatures ones correspond to “cooler”, bluish light.
|Source: Lightbulbs Direct|
COLOUR RENDERING INDEX (CRI): The ability for a light source to show an object’s ‘true colour’, which is what it would look like if viewed under sunlight. The closer a light’s CRI is to 100, the better the colour rendering.
|Source: Fusion Lamps|
MOUNTING HEIGHT: The distance between the area being illuminated and the light fixture – i.e. the height at which the fixture needs to be installed. While this may be self-explanatory, it’s very important to consider when picking a light fixture.
CERTIFICATIONS: Various ratings that certify a light fixture for use in different conditions. Light fixtures can be certified for use in different conditions, various levels of energy efficiency, performance, and durability, as well as safety. Some common ratings to look for are below – always check to see what your fixture has been certified for to prevent incorrect or unsafe usage.
WARRANTY: The guarantee of performance and durability provided with a fixture, as a mark of the manufacturer’s promise that the product will perform as advertised. As a general rule, fixtures with longer or more comprehensive warranties can be expected to last longer and be of higher quality than potential substitutes.
These basic terms are great to get you thinking about what you want to see from your light fixtures. Bring up your expectations with your electrician or contractor, and work together to find the best option for you!