Ok before you get into this you may want to look at my other post about what electricity is.
Now most electronic devices have their power usage info on them. Light bulbs usually have them on the bulb. Computers on the back of the power supply. It’s usually written on the brick that you plug into the wall when you charge your phone.
Lets just jump right in. Take this 60W, 120V bulb on my desk(I don’t like florescent lights for desk work) If I wanted to convert to amps I would simply divide watts by volts.
60W/120V = .5A
YEAH it uses .5A of power but that’s NOT what you’re getting billed for. You get billed in Kilowatt hours. So you have to add some time period.
60W * 1 Hour = 60 WattHours = .06KWh
Now if we know that our electric company charges $0.10 a KWh
.06KWh * $0.10 = $0.006 an hour (or 1 penny cause you KNOW they’ll round UP) to run this 60W bulb for one hour.
Ok now for the formulas in a bit more organized format;
- Convert Watts and Volts To Amps
W / V = A - Convert Amps and Watts to Volts
A * W = V - Convert Amps and Volts to Watts
V / A = W - Convert Watts to WattHours (Wh) (T is time in hours)
W * T = Wh - Convert Wh to KWh
Wh * 1000 = KWh - Get the cost of our electrical appliance over time (R is your utility Rate)
(W * T / 1000) * R = Cost
From this we can figure out pretty much the electrical cost of almost anything in our hour from looking at the little numbers on the back or bottom of the device.