Three Lighting Technologies with Huge Differences in Energy Cost
Lighting is one of the biggest energy-users in a house. The 3 main residential lighting choices are:
- Incandescent – The "old fashioned" light invented in the 1800s by Thomas Edison. Light is produced by heating a wire until it glows. VERY POOR energy efficiency (over 90% of electricity is converted to heat), and SHORT life.
- Compact Fluorescent Light (CFL) – A miniaturized and "twisted" version of fluorescent tubes commonly found in garages and businesses. Light is produced by passing electricity through a gas-filled tube. EXCELLENT energy efficiency and LONG life.
- Light Emitting Diode (LED) – A high-tech electronic "chip" that emits light when electricity passes through it. A cousin of the colored lights on most electronic devices, but perfected for general lighting purposes. SUPER-EXCELLENT energy efficiency and VERY LONG life. LED lighting is the future.
Most Important Conclusion: Incandescent bulbs have such a high energy cost that it makes sense to replace them with LEDs or CFLs even before they burn out, especially for the most-used lights. Seriously!
1. Photos – These 3 bulbs use very different amounts of electricity (Watts) to produce the same amount of light (about 800 lumens). The difference is how much extra electricity is wasted to produce heat.
|Uses 61.5 W (rated 60 W)
||Uses 8.0 W (rated 9.5 W)
||Uses 9.1 W (rated 13 W)
2. Bulb Comparisons – Numbers in parentheses are relative to the value for incandescents. This is for one light fixture.
||60 W (1)
||9.5 W (1/6)
||13 W (1/5)
||new halogens use 43 W (see Sec. 3)
||1000 hours (1)
||25,000 hours (25)
||8000 hours (8)
||1000 hrs = 8.3 months at 4 hrs/day
|Cost to buy
||LED cost is dropping quickly
|Energy cost per year
||if on 4 hrs/day, 11¢/kWh
|Energy cost per year
||if on 24/7, 11¢/kWh
|Total cost \ 25,000 hours
||total cost of bulbs plus energy
Main Lesson: Energy efficient lights are a good investment. Over the long term, incandescents (and newer halogens) are much more expensive due to their short life and enormous energy use. Incandescents are cheaper to buy, but you pay through the nose to operate them. LEDs are only a bit cheaper than CFLs to buy and operate, but LEDs are a better choice because CFLs have some downsides (see Sec. 3). Also, the cost of LEDs is decreasing and their efficiency continues to increase. Since newer lightbulb technologies have such long lifetimes, they are a long-term investment and it really pays off to consider more than just the relatively minor purchase price. [Also see this comparison.]
3. Additional Considerations
- Replace the most-used incandescents first. This saves the most energy and money.
- CFLs have a few downsides:
- New CFLs turn on at close to full brightness, but early CFLs turned on quite dim and took a minute to warm up.
- They contain a tiny amount of mercury and should be brought to a collection center for proper disposal. Some big box and other stores accept burned out CFLs.
- Unless labeled "dimmable", most CFLs will burn out quickly if put in a fixture that's on a dimmer switch.
- They are dimmer at low temperatures (but I still use a 9 W CFL in my refrigerator).
- Light is measured in lumens, not Watts. With different lighting technologies, choose a bulb that gives you the amount of light you want but uses the fewest Watts. This table is a guide (source):
- Caution about incandescent replacements (halogens): These use 43 W (instead of 60 W) to comply with new energy efficiency regulations, but many manufacturers cheat by simply making them dimmer to use less power. A true "60 W replacement" should produce about 800 lumens of light. I saw a Sylvania halogen that produces 610 lumens and a GE halogen that produces 565 lumens both deceptively labeled as "60 W replacements". (Anyway, 43 W is still an energy hog.)
- The price of LEDs depends on where you buy them. The numbers for the table in Section 2 came from reading labels at Home Depot. I noticed that the prices at my local hardware store were much higher.
- Use only bulbs labeled "dimmable" in fixtures with dimmer switches. This is a bigger concern for CFLs than LEDs.
- Pay attention to the "color temperature". The yellowish color of "soft white" or "warm white" incandescents corresponds to a color temperature of 2700K to 3000K. Color temperatures of 3500K or higher ("bright white" or "daylight") are bluer and more commonly used in stores than homes.
- Author's lighting strategy: Long ago I replaced all the incandescents in my house with early-model CFLs, including putting 9 W CFLs in my refrigerator and stove vent hood. I saved a few incandescents in a box, "just in case", but have never used them again. Now that LEDs perform well and the price has dropped, I will replace CFLs with LEDs when they burn out. Since LEDs and CFLs are longer-term investments, it may be prudent to get just one or two bulbs of a certain brand at first, to test in different locations and be sure you like the light.
Further Reading – Download "Efficient Home Lighting Choices". This article from Home Power Magazine digs deeper into the lighting choices. Readers are encouraged to visit HomePower.com and consider subscribing to the online version (it's an excellent deal and entitles you to download years of past issues).