Thirty percent of U.S. electricity goes to power homes. iStockphoto.com /EricVega

The energy we use is usually measured in kilowatt-hours (kWh); 1 kWh is equal to 1,000 watts working for one hour. In 2001, the entire world consumed 13.9 trillion kilowatt-hours (kWh) of electricity [source: Clean-Energy]. Of that global 13.9 trillion kWh, 25 percent (3.45 trillion kWh) powered electrical devices in the United States [source: IndexMundi]. And of that 3.45 trillion kWh, 1.14 trillion were used in households [source: EIA]. That's more than 30 percent of U.S. electricity going to power homes, which is more than either the commercial or the industrial sector uses [source: EIA].

Why the huge glut of energy consumption in the residential sector? Simple: Home appliances draw extreme amounts of energy. An appliance rated at 1,000 watts, left on for one hour, will use 1 kWh of electricity. Now think about all the appliances -- large and small -- you have in your home.



Over the last 30 years, the efficiency of many appliances has increased dramatically. A refrigerator manufactured in 1979 consumed between 120 and 300 kWh per month; in a post-2001 unit, that monthly range is down to 31 to 64 kWh [source: Hawaiian Electric]. But still, refrigerators are a big draw on the energy supply. And they're not alone.

Small appliances like toasters, hair dryers, coffee makers, vacuum cleaners and curling irons all use more watts than refrigerators do. Ranges and dishwashers do, too (you've probably noticed a trend -- producing heat takes lots of watts). But these big-watt items are only on for short periods of time, so they don't use as much power as an appliance that draws fewer watts but works indefinitely -- like a fridge/freezer or a water heater.

So for the biggest energy hogs in the home, we're left with the household appliances that we leave running for hours -- or days -- at a time. In this article, we'll take a look at five of the most energy-hungry appliances in our homes.

No. 5 on the list is refrigerator/freezers. Despite their huge efficiency jump in the last few decades, they still rank high in energy use.