kWh stands for kilowatt-hour.  On your electric bill, it’s a unit of how much electricity you used.  For a water bill, nearly everyone has an intuition of how much a gallon is.  We know that flushing the toilet is a lot more than drinking a glass of water.  When it comes to a kWh though, a lot people can’t gauge “how big” a kilowatt-hour is.

 

A kWh is “using 1000 watts for an hour.”

 

Let’s start with why it’s called a kilowatt-hour.  You can read it as “using 1000 watts (a kilowatt) for an hour.”  And a kilowatt is 1000 watts.  For example, if you kept a 100-watt lightbulb on for 10 hours, then you used one kilowatt-hour = 100 watts x 10 hours.  A kilowatt-hour is also using a 500-watt vacuum cleaner for 2 hours.

This still doesn’t help though, huh?  How do you know what uses how many watts?

How Big is a Watt?

Let’s try out your intuition.  Take some guesses.

How many watts does an electric fan in a house use?

How many more watts does an electric blanket use?

Does a washing machine or garage door opener use more watts?

Does an electric chainsaw use more or an electric clothes dryer?

Here are the answers.

A typical electric fan uses about 25 watts.

An electric blanket uses about 8 times more at 200 watts.

A garage door opener typically uses more watts than a washing machine.

A clothes dryer uses more than double the watts of an electric chainsaw at a whopping 3,000 watts.

Estimating Watts of Devices

Here are some general rules of thumb.

One, devices that heat up air use more watts.  This is why an electric clothes dryer is demanding, and why a electric blanket uses eight times the electricity of a fan.  It’s heating air.  Unless the device is clever, like a heat pump, heating air with electricity can get expensive.  A space heater for a room can use up to 1500 watts.  In many cases, devices are heating up air for no good reason, like many lightbulbs.  The heat is just wasting money.  That’s why many homes have switched to more efficient lightbulbs.

Two, devices that move stuff use more watts.  Something that runs electronics just won’t be as demanding as a device that moves stuff.  An electric dryer is moving wet clothes and heating the air inside.  A pool pump for a swimming pool is moving water, and water is heavy.  A saw or blender is also demanding because it’s moving extremely fast to cut through stuff.  Even a speaker with heavy bass may be using more watts than you think.  It’s moving a lot of air.

Three, devices that make a lot of noise use more watts.  Noise is moving air by banging on things.  It’s moving stuff, so noisy devices like a blender, an electric jackhammer or vacuum cleaner will use a lot of watts.  In many cases, the noise isn’t even wanted.

We’ve put together a list of household devices to help build your intuition of “how big a watt” is:

• 25 watts:  electric fan
• 50 watts:  newer TV with 32 inch screen
• 75 watts:  desktop computer
• 100 watts:  a classic 100-watt lightbulb (it’s hot!)
• 200 watts:  electric blanket
• 300 watts:  blender
• 550 watts:  vacuum cleaner
• 700 watts:  hair dryer
• 1000 watts:  deep fryer
• 1500 watts:  circular saw or a medium-sized space heater
• 2000 watts:  large swimming pool pump
• 3000 watts:  electric clothes dryer
• 5000 watts:  a space heater that can warm a room size of a garage

How Long Usually

If you are wondering what will help reduce your electricity bill, getting a sense of what type of devices are the most demanding helps, but it’s only the “kilowatt-” part of a kWh.  The “h” is for hour.  Everyone has a sense of how long an hour is, so the last part to consider is how long you would usually use a device.

Here are some example of thinking about time in making trade-offs in cutting your electric bill.

Let’s say your bedroom is really cold at night.  An electric blanket for 8 hours is much better than a space heater for 8 hours.  This is 200 watt versus 1500 watts for the same amount of time.  Further, some people find an electric blanket to get too hot in the middle of the night, so a timer that turns off the blanket after 2 hours would be best on your body and on your wallet.

100-watt lightbulbs versus a blender.  A blender uses three times the power at 300 watts, but unless you run a smoothie shop out of your home, a blender for a few minutes doesn’t compare to several lightbulbs for hours on end.  Also, stirring and chopping things is crazy hard, but changing to efficient lightbulbs is easy.

Should you spend energy finding bunch of small savings or just be more careful how the swimming pool pump is used?  A pool pump is easy to forget about and can be running even when no one is using the pool or even when the water is too cold to jump into.  Being more careful with the pool pump is just one thing to stop a 2000 watt load unnecessarily for hours on end.  That beats nickel-and-diming yourself everywhere.

Reducing kWh’s on Your Bill

A kWh is using 1000 watts for an hour.  Devices that get hot, noisy and/or move stuff will generally use a lot more watts.  First, consider the devices that are both demanding (high watts) and you usually use for fairly long time.  The worst are those that are easy to forget about, like a pool pump or an old refrigerator in the garage.  Knock out the big ones that you can control with one-time fixes.  For what’s left, worry less about devices you seldom use and is kept unplugged.  Consider devices that you use a lot longer or devices that are always plugged in.