Energy Efficiency

Light Switch Calculator

Compact fluorescent light bulbs are a great way to save energy in your home. They cost more to buy but quickly return that money through lower monthly utility bills. Use this calculator to see how much your family might save by replacing standard 100-watt light bulbs with new compact fluorescents.

Incandescent Lamp Wattage:	25 40 60 75 100 150
Number of Bulbs Used:	1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40
Number of Hours "On" Per Day:	1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Cost Per kWh:

Type of Bulb	Total Cost Per Month
-watt Standard Incandescent Light Bulb	$
-watt Compact Fluorescent Light Bulb	$
Savings Per Month:	$
Savings Per Year:	$

In addition to these savings on utility bills, compact fluorescents last almost 10 times longer than standard incandescent lamps and give off one-quarter as much heat.

See if you can solve these:

1. If you have 5 100-watt light bulbs and they burn about 5 hours per day, at 8 cent/kWh, how much do they cost?

2. How much would it have cost if your home had compact fluorescent lamps?

3. What is the difference each month between the cost to operate the standard bulb and the compact fluorescent?

4. If a candy bar costs 50 cents, how many candy bars could you buy with the savings?

5. How many 50-cent candy bars could you buy with the savings over a year?

6. If the compact fluorescent bulb costs $6, how many months would it take to save enough to buy one?

7. How many could you buy with your yearly savings?