One watt (1W) is not a lot of power. It can’t charge your cell phone or even an LED night light. So why should you care about eliminating vampire loads of one or a few watts? The answer is that every little bit helps and that 1W on all day everyday does add up to something. Also, if you know how much 1W costs you and the environment, then you can easily figure out how much 10W or 100W will cost you, or better yet save you if you can eliminate them.
Math warning – a little bit of multiplication
Calculating Energy – 8.76 kWh
- Power X Time = Energy
- 1 W x 8,760 hours ( 24×365 hours in a year) = 8.76 kWh (1 Watt for 1 year)
note the division by 1,000 to go from Wh to kWh (the unit you see on your electric bill)
So, 1 W on all the time uses about 9 kWh of electricity a year.
Estimating Cost/Savings – $1.43
- Energy X Cost of Energy (electricity in this case) = Cost
- 8.76 kWh x 16.36 ¢/kWh (MA residential rate from 10/09) = $1.43
So, 1W on all the time costs about a dollar fifty per year. You can find out the average retail price of electricity in your area from the US Energy Information Administration’s report.
Estimating CO2 Emissions – 11 lbs CO2
- Energy X lbs CO2/kWh = CO2 Emissions
- 8.76 kWh X 1.263 lbs CO2/kWh (for MA in 2005) = 11 lbs CO2
(Updated Data – 0.93 lbs CO2/kWh for NPCC New England (NEWE))
You have to do a little math to convert from lb/MWh to lb/kWh provided by the EPA’s eGridWeb.
Just divide by 1,000 or shift the decimal point 3 digits to the left.
- Updated for 2009 data for MA – 0.734 lbs CO2/kWh (CO2 equivalent)
So, 1 W on all the time generates about 11 pounds of CO2.
Adding it All Up
One Watt (1W) by itself really isn’t that much, but when you consider you probably have dozens of devices that are needlessly drawing 1-30 W all day, everyday, you should be able to find plenty of savings opportunities. Three big ones to look at are old VCRs, Cable Boxes and PCs.
|Power (W)||Annual Energy Usage (kWh)||Annual Cost||Annual CO2|
|VCR – left on||8 W||70 kWh||$11||88 pounds|
|Cable Box – “turned off”)||25 W||219 kWh||$36||277 pounds|
|Personal Computer (Desktop) – left on||75 W||657 kWh||$107||830 pounds|
So while 1 W may only almost light up an LED, adding all the unnecessary ones together around the house they can add up to tons of CO2 emissions every year. Go around your home and find the things that do not need to be plugged in all the time and unplug them. If you have a kill-a-watt meter make a list of everything plugged in and measure how much energy each device really uses. Hint, start with the easy to reach outlets and big appliances and work your way through the house. Before long you will be savings lots of energy and money.