Hi everyone… seems like a bit of basics is in order. Since my previous post about the kill-a-watt device was becoming too long, I’d like to continue discussing about the Power equation in this article… to recap:

Power (Watts) = Voltage (Volts) x Current (Amps)

This is the essential equation you’ll need to know in order to figure out energy (electricity) usage in your home.  The main thing to figure out is the total number of watts or power you will need for your home - and you can do this by going through each of the devices/appliances you use and recording the number of watts it uses.

Again, you can use a Kill-A-Watt or an ammeter or any other similar device to measure wattage and current to come to the same values but if you don’t have these gadgets handy, then there’s an easy way to estimate the maximum power each device needs.. by just using the equation above!

The trick is to look at each device and look either at the back of the device, or under it, or on its plug adapter for a sticker or piece of paper with some technical information about it (like the model number, date manufactured, manufacturer, etc).  This is required to be there for all electrical appliances and devices so it should be there somewhere. (If you really can’t find it anywhere, then you can just look in that device’s user’s manual - usually in the technical specifications page for this same information)

Usually, in that sticker comes the electrical information in Volts, Amps or Watts or a combination of each. Just ignore everything else written in there since most of them are not for us normal people.  Some of them may have the watts written on it (look for a Watts or W), or may only have Volts (V) and Amps (A), or maybe just even Amps (A).  Here’s how to figure out the number of maximum watts the device could use:

  • If you find Volts (V) and Amps(A), just multiply them together to get Watts. (i.e. 110 Volts x 2 Amps = 220 Watts).
  • If you find only Amps(A), then just multiply it by 110 V (standard on most U.S. homes) or 220 V depending on your home’s voltage. (i.e. If the rating is 5A, then multiply that by 110V to get 550 watts).

Of course, if the number of watts is already written in there, then there’s no need to calculate anything! :)

Here are some samples that I got from around the house:

Laptop sticker showing Voltage & Amps

Laptop sticker showing Voltage & Amps

This one is from my Toshiba laptop found under the laptop near the power supply. It’s clearly shown here the volts (DC 15V) and amps (5A). So, in effect, the total wattage my laptop can use is 75 watts.

Fridge Sticker sample

Fridge Sticker sample

This is an example of my “Energy Star” fridge. I found it inside the refrigerator on the left hand side (yours may be different but its usually somewhere inside the fridge). You can easily see the “Amps-4.50″ and “Volts-115″ values in there. Pretty easy… so the total watts needed is about 518 watts (115 times 4.5).

Rice Cooker sticker sample

Rice Cooker sticker sample

This is a sample of a rice cooker appliance. In this case, there’s no need to calculate anything.. it says it right there.. “850W” or 850 watts!

In addition, if you want to get the current (Amps) for this appliance, just use the sample equation and just divide the Watts by Volts (120V in this sticker)… to get 7 Amps!

I certainly hope this has given you a much clearer understanding of finding out power usage for your devices. If you keep a good record of this, it will come in pretty handy later on when you want to add generators or inverters to power your home in the future.

Finally, It’s also a good thing to know how much power your appliances use to be more conscious of power usage and to take steps to save on your electricity bill the next time it comes around!