How much energy can light produce?

Light energy can be measured a few different ways, the old way was called “candlepower”. This was the amount of light produced by a standard 75g candle for 1 square foot around the candle itself.

LED light technology is usually labeled in lumens, since the amount of electricity needed to produce light is much lower. For example an old fashioned 100 watt light bulb used 100 W of electricity to produce 1,600 lumens of light. This is a really bright bulb and can hurt your eyes if you’re too close to the light bulb.

Unfortunately, it’s very difficult to produce a standard amount of light from a single candle, since burning a candle can produce lots of different colors, sizes and intensity of light. A more accurate way to standardize light is to measure the brightness of a light emitted from a tungsten wire with a set amount of electricity. This unit is called a “lumen”, or the amount of light emitted in a 1 meter sphere.

Light bulbs used in the house are often labeled with the amount of electricity they use to produce the brightest amount of light, these are measured in Watts. A 100 watt light bulb is much brighter that a 50 watt light bulb, but is also uses twice the amount of electricity.

But, to produce 1,600 lumens of LED light uses only 15W of electricity, that’s less than one sixth of the electricity to produce the same amount of light! By switching to LED technology your family can cut costs to 1/6 on their energy bill. That means if an electrical bill cost $300/month, switching to LED light bulbs will drop the cost to $50/month and save your family $250 every month!

Explore you house and record how many light bulbs are being used in each room, and write down if they are standard light bulbs with watts or LED light bulbs. Add up the amount of watts being used in the house and use the chart below to see how many LED light bulbs are needed to produce the same amount of light.