NEW YORK (CNN/Money) - In an emergency or black-out, you'll want to keep your crucial appliances running -- and that means a generator. But these handy machines can be tricky to use.

In today's 5 Tips Home Edition, we'll tell you how to safely use a generator to keep your house supplied with electricity.

You have a greater chance of carbon monoxide poisoning if you run a generator indoors than you would if you sat in an idling car with the garage door closed, according to Scott Wolfson of the US Consumer Product Safety Commission.

Most generator-related deaths are a result of carbon monoxide poisoning. The gas is undetectable. It's odorless and colorless. Don't ever keep a generator running in your home, your garage, your basement or your shed.

Once it's outside, make sure your generator is far away from any windows or ducts so that fumes can't be carried into the house by the wind. If at any time you feel dizzy, nauseous or weak, leave immediately and seek fresh air.

Generators are not meant to be near any kind of water. You run the risk of electric shock. You should not use your generator if it's raining or if there's a lot of moisture in the air.

If it does start to rain, turn off the generator and put it in a dry location. Make sure your hands are not wet before touching the machine. Ideally your generator should be kept on a dry, flat surface.

Portable generators are meant to supply energy to one or two electrical appliances. Don't make the mistake of plugging your generator into a wall outlet or your home's electrical system. You can blow out your system, and you're also putting any electrical workers in danger of electrocution if they happen to be working on fallen power lines in the area. Buy a heavy-duty outdoor rated extension cord that is free of cuts and has all three prongs.

When buying a portable generator, you'll want to match the size of your generator to your electrical needs.

To calculate what size generator you need, get the total wattage of the appliances you want to power. You should choose a generator with wattage at least equal to that total, according to Consumer Reports.

To find the wattage for your appliances, refer to your owner's manual or look on the appliance itself. A mid-sized portable model runs up to 7,000 watts and can power a computer, a water pump, a furnace fan and an air conditioner. For more information on what of wattage your appliances need or what kind of generator you should buy, click here.

You can easily buy generators that cost over $10,000 dollars, but your family will probably be just fine with portable mid-size models that cost around $800. You can buy generators through electricians or large home retail centers like Home Depot or Lowes.

In an emergency gasoline is going to be tough to find. During a power outage, gas station pumps don't work.

A typical portable generator will go through about 12 gallons of fuel a day. If you've been hit with a storm that knocks out power for 3 days, that's going to be problem unless you can store all these supplies.

Plus, gas can go bad. If you have gas in your tank, it may break down in about six months without gas stabilizers, according to Peter Sawchuck of Consumer Reports.

Consider using propane tanks. You'll have more luck finding propane tanks from barbeques after a hurricane than you'll find gas supplies. And propane is easier to store.

And while rare, you can find natural gas generators, which would be a better fit because the fuel is more readily available. The downside is that these generators are just not as powerful.

Gerri Willis is a personal finance editor for CNN Business News and the host for Open House. E-mail comments to 5tips@cnn.com.