Getting the most out of portable generators

Portable generators can keep the convenience of electricity flowing during a power outage.
Getting the most out of portable generators

Portable generators can keep the convenience of electricity flowing during a power outage. For those who rely on home life-support systems, these devices become an absolute necessity.

The amount of electricity available is directly dependent on fuel readily at hand. For this reason, efficient use of portable generators is important in keeping temporary power flowing in your residence during an outage.

Proper size

The first and most important step toward efficiency starts with size. The larger the generator, the more fuel it requires to operate, regardless of load.

To determine the size you'll need, make a list of appliances you want to run in the event of an outage. Find both starting and running wattage requirements on appliance nameplates or in owner's manuals; then add them up to determine the total wattage. Although the starting wattage will last for only a few seconds, the generator must be able to meet it to run safely. Once you have a total, scale the generator up a size or two to ensure safe, efficient operation.

Comparing fuels

All generators operate by converting mechanical energy, produced by fuel combustion, to a DC current (or an alternating, or AC, current in some cases). Generators typically use one of four fuel types: gasoline, diesel, propane or natural gas.

Gasoline remains the most common fuel source for residential portable generators. However, gasoline is highly flammable, has a short shelf life, and doesn't burn as efficiently as diesel.

For loads larger than 30 kilowatts, diesel is a less expensive option. Diesel is the least flammable and generally can be obtained in an emergency because of its military, trucking and farming uses. Diesel also has a longer shelf life than gasoline, although diesel engine noise can be louder compared to gasoline, with the engines subject to smoke if not properly maintained. A typical 20-kw diesel generator can run a large home.

Propane boasts a long shelf life, is clean burning, obtainable during power outages, produces quieter engine noise, and is more emissions compliant. Disadvantages include more complicated fuel systems with larger tanks — propane-fired generators are usually less expensive to buy and to operate, but they don't last as long as diesel or gasoline models.

Clean-burning natural gas can be supplied through a larger distribution system, making it virtually limitless for supplemental generation. However, natural gas-burning generators deliver lower power outputs (Btu per unit) than gasoline engines, have higher installation costs, require three times the fuel compared to diesel, and can be dangerous if lines are broken. Also, during natural disasters gas lines are usually the first to be shut off for safety reasons.

Scott Gates wrote this for the National Rural Electric Cooperative Association.

Sample wattages graph

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