Energy Efficient Lighting Guide
Learn how to switch to LED lighting, understand lumens versus watts, and calculate your annual energy savings when upgrading incandescent bulbs.
In this guide
- Understand lumens vs. watts
- Compare LED and incandescent efficiency
- Calculate LED energy savings
- Find the right color temperature
- Identify hidden lighting costs
Switching to LED lighting reduces lighting energy consumption by up to 85%. Because LEDs are so efficient, you must shop by lumens (brightness) rather than watts (energy used) to find the correct replacement for an old incandescent bulb.
Lumens versus watts
For decades, consumers purchased lightbulbs based on wattage. A 100-watt bulb was brighter than a 60-watt bulb. However, watts measure energy consumption, not brightness. Because LED technology is vastly more efficient, a modern 9-watt LED can produce the exact same brightness as an old 60-watt incandescent bulb.
To shop for lighting today, you must look at lumens, which directly measure light output. A standard 60-watt incandescent bulb produces about 800 lumens. When replacing it, simply look for an LED bulb that offers 800 lumens, regardless of its wattage.
Why LEDs are more efficient
Traditional incandescent bulbs are essentially small heaters that happen to glow. They convert roughly 90% of the electricity they consume into heat, leaving only 10% for visible light. LEDs (Light Emitting Diodes) use a semiconductor process that converts electricity directly into light, producing virtually no wasted heat. This lack of thermal waste is why they consume 75% to 85% less power and last significantly longer.
Calculating your savings
To calculate the financial benefit of upgrading to LEDs, you must determine the wattage difference between the old bulb and the new bulb, convert that difference into kilowatt-hours based on your usage, and multiply by your electricity rate.
Definitions
- Old Watts: The wattage of the incandescent bulb.
- New Watts: The wattage of the replacement LED bulb.
- Hours Used: How long the bulb is turned on.
Example
Replacing a 60W bulb with a 9W LED saves 51 watts. Over 1,000 hours at $0.15/kWh, the savings equals (51 ÷ 1,000) × 1,000 × $0.15 = $7.65 per bulb.
Understanding color temperature
Beyond brightness (lumens), LED packaging lists a color temperature measured in Kelvin (K). This dictates how "warm" or "cool" the light appears.
- Soft White (2700K - 3000K): Warm, yellowish light similar to traditional incandescents. Best for bedrooms and living rooms.
- Cool White (3500K - 4100K): Neutral white light. Good for kitchens and workspaces.
- Daylight (5000K - 6500K): Bright, bluish-white light. Ideal for reading lamps, garages, and security lighting.
Worked replacement example
Assume a homeowner replaces ten 60W incandescent bulbs with 9W LEDs. The bulbs are used for 4 hours per day, every day, and the local electricity rate is $0.16/kWh.
| Metric | Incandescent (10x 60W) | LED (10x 9W) |
|---|---|---|
| Total Wattage | 600 W | 90 W |
| Daily Energy (4 hrs) | 2.4 kWh | 0.36 kWh |
| Annual Energy (365 days) | 876 kWh | 131.4 kWh |
| Annual Cost (at $0.16) | $140.16 | $21.02 |
| Annual Savings | - | $119.14 |
Limitations to consider
For more information on our calculations, please read our Methodology and Disclaimer.