A few reference links...
• Fossil Fuel Power Station Efficiency
• CFL and Bulb Efficiency
• Converter of Units
You don't know me. I live in this subdivision a few blocks north of you on a different street. I drive by your house on my way to and from work. For much of this year, I notice the five incandescent lights in your garage are turned ON. It doesn't seem to matter what time of day. They are visible through the windows in your garage door. Your lights are often ON when your door is open in broad daylight.
I am concerned about the environment and the waste of natural resources. I taught science to high school students for 38 years and stressed to them the importance of conservation. Seeing your lights ON unnecessarily so much of the time brings about two questions. First, what is the cost in dollars, and the cost to the environment? Second, what can be done to reduce those costs? Yes. I am going to tell you answers to both.
What is the Cost?
First the $$$...
10 h/day x 30 day/mo x 12mo/yr = 3600 hours per year of time
Energy = power x time = 0.500 kW x 3600 h = 1800 kWh of electric energy
1800 kWh x $0.10 per kWh = $180 each year based on our utility bill figures
Now the resource...
1800 kWh x 3,600,000 Joules/kW = 6,480,000,000 Joules to light your bulbs
A Joule is about the energy needed to lift an apple from the floor to the counter.
6,480,000,000 Joules = 0.33 x power plant energy
Plant burns coal to make 19,640,000,000 Joules so you get 6,480,000,000 Joules.
A kilogram of hard coal (2.2 lbs) makes 29,310,000 Joules of heat energy when burned.
19,640,000,000 Joules x 1 kg/29,310,000 Joules = 670 kg = 1480 lb of coal
This figure does not include the mining and transportation costs to get the coal.
How to Reduce the Cost?
Buy Compact Fluorescent bulbs.
Use CFL bulbs and turn them OFF when not needed to save even more.
Don't be offended by my note to you. Yes, I may have overstepped my boundary. But, as a concerned citizen of the Earth, I feel it is up to all of us to do our part to help save resources and keep our planet habitable. There are many simple things we can do. This is one of them. Education is the way to bring that to the attention of people such as yourself. It's easy to follow our habits and forget some simple actions that can have some big consequences. I trust you understand.