Light Lumens Vs. Watts Explained – A Homeowner’s Lighting Guide

Any lighting fixture has various ways of being described. For example, a single lamp can provide a certain amount of light, a certain power of light and even a certain color. One way in which all lights are describes is in terms of “lumens” or the total amount of light produced by the lamp. This sort of description takes into account not only the power of the light, but the efficiency of the entire system to which it belongs. This is often viewed in terms of “lumens per watt” and is actually quite similar to “miles per gallon” in a vehicle.

For example, lumens per watt is a way of noting how many lumens the user gets from a light source compared to the amount of energy (wattage) used. Just as a car that gets the highest number of miles from a single gallon of fuel is considered optimal, so too is the lamp that provides the most lumens for the lowest wattage. Traditional lighting (incandescent lamps) provides between 17 to 20 lumens per watt where a fluorescent lamp tends to pack an impressive 90 lumens per watt. This is obviously the reason that so many commercial spaces rely on fluorescent lighting.

Unfortunately, the lumens per watt ratio is not constant and as a lamp degrades, so too do the numbers. Most lamps are designed to perform at certain levels, and just like vehicles, they may begin at these higher rates, but over time and as wear and tear take their tolls, the rates decline. Most manufacturers will list the LPW figure on the product, and a savvy consumer should anticipate to lose roughly 33% of that figure over the life of the lamp. So, what does all of this really mean? It adds up to a lot of valuable information for a consumer, or even a business owner, outfitting their home or office with lighting fixtures. By paying attention to the numbers provided, a consumer can get a really good idea of the cost of operating the lamp over the course of a year or over the course of the fixture’s life span.

For instance, most fixtures see around 4,000 hours of operation in commercial locations each year. This means that a compact fluorescent bulb of 32 watts is going to provide roughly 1920 lumens of maintained life. At this rate, and using a nationally average figure, the lamp will cost roughly $12.80 to operate over the course of a year. Interestingly, a one hundred watt incandescent bulb will cost around $40 for the year. Obviously this is one of the reasons to pay close attention to lumens when considering types of outdoor lighting like in solar flag lights.