Well, Xcel Energy has already done the math for me:
"Amount of Electricity Used
We’ll need to begin with the amount of light bulbs in a home. According to a recent survey, the average American household uses 47 light bulbs.
Now, these bulbs might have varying wattages from 100 watts down to 25, but for the sake of easy math and comparisons, let’s assume that we are using all 60 watt bulbs.
Total Light Wattage = 47 bulbs X 60 watts = 2,820 watts
That’s a lot of wattage! Now let’s take a look at the wattage if all 47 lights are CFL bulbs or LED bulbs at the equivalent brightness of 60 watt incandescent bulbs.
|All bulbs deliver equivalent brightness||Single bulb wattage||Wattage used for whole house|
As you can see, there is quite a difference in the wattage between energy efficient bulbs and incandescent bulbs. In other words, switching to CFL or LED bulbs would save A LOT of energy. And as I’m about to show you, this will, in turn, save a lot of money!
Cost of Electricity
The average cost of electricity in the United States is currently 11.88 cents per kilowatt hour (kWh) (for a more accurate cost, you can check your last billing statement for your cost per kWh), meaning if you used 1,000 watts of electricity for an hour, it costs you 11.41 cents.
Time that Lights are Turned On
The amount of time the lights are being used can vary quite a bit from home-to-home, but let’s pretend, for the sake of this example, that each of us use our lights for 5 hours a day. That’s 30 days in a month (on average), for 5 hours a day.
5 hours X 30 days = 150 hours
Now that we have all of the necessary factors, we can calculate the difference in cost of using traditional incandescent light bulbs versus energy-efficient CFL and LED light bulbs. The formula for this is below:
kW used X (Cost per kWh) X Hours Used = Monthly Lighting Costs
Remember, a kilowatt (kW) is 1,000 watts, so we divide our wattage by 1,000 for this formula.
Monthly Cost of Using Incandescent Light Bulbs
2.820 X $0.1188 X 150 hours = $50.25
Monthly Cost of Using CFL Bulbs
0.658 X $0.1188 X 150 hours = $11.73
Monthly Cost of Using LED Bulbs
0.470 X $0.1188 X 150 hours = $8.37
If, in this scenario, I switched 47 incandescent light bulbs to LEDs, I could save around $41.87 each month, (or $10.69 per bulb per year). That really adds up over the course of a year, and the savings continue to grow over many years."
Most households probably aren't using quite that much energy just for lighting, so you should consider the above example a "best case" scenario.
IKEA is now selling a dimmable A19 bulb for only $4.49 plus sales tax. So if this bulb were appropriate for every fixture in the house above, the total cost to refit the entire house would be only $226, with a payback period of less than 6 months. That's still a great investment even if you only use your lights half that much.
The fact that these bulbs are supposed to last for over 20 years, makes it even a sweeter deal.