You don't realize how much you rely upon steady electrical power each and every day until it goes out - that is, unless you have a standby generator for just those emergencies. It can, however, be difficult to decide just what sort of backup generator to use when there are so many options to choose from. Whether sourcing for an apartment block sized residential generator or a portable generator for camping excursions, the dizzying array of available standby generators.

There are three general things you'll need to consider to make a good decision, aside from the heft of your pocketbook:

• required amount of power
  
  
• environment it will be used in
  
  
• available fuel sources and running time

Firstly, the amount of power you'll require in your backup generator is a function of a steady or nominal load and the maximum, likely peak usage. This is easy to figure out in the case of light bulbs, as their power usage (measured in watts) is stamped right on the glass.

Other appliances may be a bit more difficult to find, but there should either be a tab indicating how many watts are used or the total number of amperes (amps). The number of watts can be determined by simply multiplying the number of amperes by 120 (volts) in North America or by 220 (volts) in much of the rest of the world, including the EU.

Once you have a power sum of all the devices you absolutely need to run in the event of an emergency, add about 20% to that figure (multiply by 1.2), and you'll have some headroom to ensure everything continues to operate even when all the devices are pulling current from the standby generator at the same time.

By performing such calculations and very thoroughly determining the likely median and peak loads, you can get a pretty good idea what size standby generator you'll need. Even with adequate headroom, you may want to stagger the power on sequence for each large device. Devices that handle a lot of power, such as appliances, can pull as much as three times their normal load during the power-on cycle. Just plug them in one at a time after

The type of fuel you'll want to use with your generator will not only have a large impact on the price but also, the versatility and potential uses of any standby generator. The most common types of fuel used are:

• gasoline / petrol
  
  
• kerosene
  
  
• diesel / bio-diesel
  
  
• natural gas
  
  
• propane / LP

Like an engine, just about anything that can burn and is concentrated enough can power a standby generator, and petroleum products are most often used. It is useful to note that the exhaust of all these fuels is rich in carbon monoxide and they really, truly must not be used indoors. The best place to keep the unit is outdoors, under cover. An attached garage doesn't count as outside. An outbuilding or shed is far more appropriate.

It is always a good idea to consider, not only the fumes one might produce with a standby generator, but where the fuel will come from. For instance, if the only source of kerosene in your area is to counties away, one might want to consider using another source. Those who are concerned about the ever-increasing cost and potentially spotty availability of petroleum products might consider a diesel burning generator that can be used with either type of fuel (since they are essentially the same thing).

For those sourcing a portable generator for industrial applications, there are a few uses where even the more benign components of exhaust can cause unusual side effects. For instance, they cannot be used anywhere near greenhouses or food storage facilities because they produce the gaseous plant hormone ethylene that makes food ripen and spoil. Some locations are not suitable for noise, no matter what. Portable generators are most often used in such applications, otherwise most standby generators are somewhat noisy.

Choosing a brand to go with can be difficult, though many manufacturers have a speciality. This is usually apparent when you look at their product line with an eye toward products they have many permutations of. It's a good idea to check out at least 5 different vendors, though a search for capabilities is often of greater use, since you'll know generally what sort of capability you need based upon the three criteria above.

The purchase of an emergency or standby generator is no small undertaking. Prices can range from $300 to $30,000 US dollars depending upon the size, capability and fuel source. For residential use, generators in the 7-15 kilowatt range are common, though the number of appliances you absolutely require the generator to run may shrink in size when the price steeply increases with each additional watt.

Armed with a tailor-made set of requirements, you can confidently plan to keep the power on in an emergency for years to come.