How much is that light bulb costing you?

I decided I wanted to learn about electricity.  Electricity in general, but especially as it pertains to solar energy.  So I went out and bought some solar panels to try and figure it all out.  This will be a 2 part blog posting.  One about the cost of electricity to you, and a second specifically on solar energy.

You pay your electric bill based on Watts.  Or more specifically, kWh (kilowatt hours), which means how many 1000 Watts you use in an hour.  If you look at your actual bill, it's confusing, but you can simply divide your bill total by how many kWh you used.  I pay about $0.12 per kWh.

So just how much electricity do your devices use?  I purchased something called a Kill A Watt meter that measures for you right at the wall.  It's very easy to use.  I recommend getting one.  I went all around the house, checking different appliances and how much power they use.

So how much does it cost to run your device?  Well take a lamp with a 65W light bulb.  Not surprisingly, that uses 65 watts.  So the formula to calculate usage cost is wattage * hours used / 1000 * price per kWh.  So the formula for running my 65W light a full day is 65 watts * 24 hours / 1000 * 0.12 price per kWh = $0.1872 or about 19 cents.

Here is a spreadsheet I made of a bunch of stuff I measured:

Item	Watts	Per Day	Per Month	Per Year
Home Laptop	18	$         0.05	$         1.56	$         18.92
Work Laptop	18	$         0.05	$         1.56	$         18.92
Hannspree Monitor	23	$         0.07	$         1.99	$         24.18
Acer Monitor	41	$         0.12	$         3.54	$         43.10
Speakers	2.2	$         0.01	$         0.19	$           2.31
Network switch	5.8	$         0.02	$         0.50	$           6.10
Wireless Phone	1.4	$         0.00	$         0.12	$           1.47
printer	5	$         0.01	$         0.43	$           5.26
desktop computer	77	$         0.22	$         6.65	$         80.94
box fan	81	$         0.23	$         7.00	$         85.15
piano keyboard	2.5	$         0.01	$         0.22	$           2.63
cell phone charging	5	$         0.01	$         0.43	$           5.26
shredder	1	$         0.00	$         0.09	$           1.05
50" LCD TV	350	$         1.01	$       30.24	$      367.92
Playstation	74	$         0.21	$         6.39	$         77.79
DVR	26	$         0.07	$         2.25	$         27.33
Toaster	785	$         2.26	$       67.82	$      825.19
Microwave	1422	$         4.10	$     122.86	$   1,494.81
Fridge	195	$         0.56	$       16.85	$      204.98
Light bulb	65	$         0.19	$         5.62	$         68.33

Some other interesting notes:

• Do devices still suck power even when they are off?  Some do, but for most devices no.  The shredder used 1W on or off.  The Hannspree monitor used 0W off, and 0.8W when the computer was asleep.  The Acer monitor used 0.4W off.  The microwave used 2W off.  The biggest culprit was the DVR that used 19W off, presumably because it was still trying to record even when it was "off".  Most everything else didn't use anything when off (TV, playstation, toaster, cell phone charger, etc.)
• Depending on what you are doing, you'll use a different amount of wattage: For example, my laptop would go up to 22 watts when watching a movie.  I actually made my desktop computer spike up to 350 watts doing something I knew was super intensive.
• Lights in devices: The microwave used 30 watts when the door was open, and 2 watts when the door was closed (but not running).  The fridge/freezer similarly used 2 watts with the door closed, 87 watts with the door open, and 195 watts with the door closed, but the motor running.  It took me a little detective work to figure it out, but it was the wattage the light bulb was using.
• Fans:  My box fan used 126 watts at the 3 setting, 103 watts at the 2 setting, and 81 watts at the 1 setting.
• My keyboard used 2.5 watts at rest, and 4-7 watts while I was playing it.