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Light bulb census

Color how many incandescent, compact fluorescent, and LED lights you have in your home and calculate how much you might save if you switch everything to LED lights

Data sources

For light bulb energy use, cost, and bulb life: How Energy-Efficient Light Bulbs Compare with Traditional Incandescents. United States Department of Energy. Accessed February 2017.

	Incandescent (60W)	CFL (60W)	LED (60W)
Energy saved (%)	0%	~75%	~75%-80%
Annual energy cost*	$4.80	$1.20	$1.00
Bulb Life (hours)	1,000	10,000	25,000

* Based on 2 hrs/day of usage, an electricity rate of 11 cents per kilowatt-hour, shown in U.S. dollars.

Light bulb costs per bulb were taken from Amazon on February 2017:

Incandescent Bulbs - $1.53/bulb on February 2017
Compact Fluorescent Bulbs - $2.20/bulb on February 2017
LED Bulbs - $3.86/bulb on February 2017

How the data was used

To calculate how much money that could be saved on energy use annually per bulb switched to LED light bulb:

watts x 3 hours/day x 365 days / 1000 watts/kilowatts = kilowatts-hours of energy per light bulb per year
killowatts-hours/year * $0.11 / kilowatt-hour = energy cost per light bulb per year

To calculate how much money that could be saved on light bulb replacement annually per bulb switched to LED light bulb:

bulb life (hours) / 24 / 365 = bulb life in years
bulb cost ($) / bulb life (years) = cost of bulb replacement per year

The two values above are then added to get the total savings annually per bulb switched to LED.

To calculate the tons of CO2 emissions saved annually per bulb switched to LED, we use the Greenhouse Gases Equivalencies Calculator - Calculations and References:

killowatts-hours/year x 1,671 pounds CO2 / MWh delivered electricity x 1 MWh / 1,000 kWh x 1 metric ton / 2,204.6 lbs = Metric tons of CO2 emissions reduced annually per bulb switched to LED

Code

A python script is available in the code repository to generate or extend this activity, and can be run like this:

python lightbulbs.py

Which will simply create an svg file with 50 light bulbs for each group: Incandescent, CFL, LED and the amount of money that could be saved annually per bulb switched to LED.