LED vs Traditional Lighting
Efficiency Comparison
Compare LightsLighting technology has evolved dramatically. LEDs now produce the same light as incandescent bulbs using 75-85% less energy. Understanding efficiency helps you choose wisely.
Equivalent Bulb Wattages
| Light Output | Incandescent | CFL | LED |
|---|---|---|---|
| 450 lm | 40W | 9-11W | 4-5W |
| 800 lm | 60W | 13-15W | 8-10W |
| 1100 lm | 75W | 18-20W | 11-13W |
| 1600 lm | 100W | 23-25W | 15-18W |
What Lighting Efficiency Measures
A light source's efficiency is its luminous efficacy: the visible light it produces for each unit of electrical power it draws, reported in lumens per watt (lm/W). A lumen measures luminous flux, the total visible light leaving the bulb. A watt measures the power going in. Divide output by input and you can compare any two bulbs, whatever their technology.
The Units Behind the Numbers
A few photometric units build on the lumen:
- Lumen (lm): luminous flux, the light output printed on the package.
- Candela (cd): luminous intensity, the light sent in one direction.
- Lux (lx): illuminance, one lumen over one square metre (1 lx = 1 lm/m²).
Labels carry two more figures. Color temperature, in kelvin (K), runs from warm 2700 K tones to cool daylight near 5000-6500 K. The color rendering index (CRI) rates how faithfully colors appear, on a scale up to 100.
Working Out the Figures
Efficacy is a quick division. An 800-lumen LED drawing 9 watts delivers about 89 lm/W (800 ÷ 9), while 800 lumens from a 60-watt incandescent gives roughly 13 lm/W. Physics caps the result: the theoretical maximum is 683 lm/W, reached only by green light at 555 nanometres, the wavelength the eye sees best.
Running cost comes from power and time. Multiply watts by hours, then divide by 1,000 for kilowatt-hours (kWh). A 10-watt LED run for 1,000 hours uses 10 kWh, against 60 kWh for a 60-watt bulb. Multiply kWh by your electricity rate for the cost.
Where the Comparison Matters
Efficacy guides choices at every scale. At home, switching high-use fixtures to LED trims the biggest slice of a lighting bill, because those bulbs burn the most hours. Offices and warehouses track efficacy closely, and the lower heat of LEDs eases the load on air conditioning. Street and stadium lighting favors LEDs for long service life, which cuts the labor of reaching and replacing fixtures. When you read a package, match lumens to the brightness you want, pick a color temperature to suit the room, and read wattage only as energy drawn.
Conclusion
LEDs are 5-10× more efficient than incandescent and last 25-50× longer. Despite higher upfront cost, LEDs save money over their lifetime through reduced energy use and replacement costs. For equivalent brightness, compare lumens, not watts.