Sipping Power
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.
But generator owners are put in a unique position once an outage occurs and electric co-op line crews begin work to restore power. Instead of drawing power from a far away, seemingly limitless fuel source, the amount of electricity available becomes directly dependent on fuel readily at hand.
For this reason, efficient use of portable generators can go a long way in keeping temporary power flowing in your residence during an outage. The first and most important step starts long before the power goes out: properly sizing the generator. 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 the 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.
Fuel is another consideration. 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. What’s more, home generators for loads larger than 30 kW are essentially car engines, produced by Ford or General Motors (up to 225 kW). Diesel is a less expensive option for this size load.
Diesel is the least flammable source 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,” says Fish. “If that unit is fully loaded, it will burn about 1.6 gallons of diesel fuel per hour. If the generator is only loaded to one-quarter of its capacity [roughly 5 kW], it will typically burn about 0.6 gallons of diesel fuel per hour.”
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 to a home 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 natural gas lines are broken.
The bottom line is, each generator has different efficiencies and will produce different results. Do your homework ahead of time to find the right generator for your needs. And once you bring that perfect model home, invest in at least quarterly maintenance inspections by a qualified generator contractor.
Sources: Scott Gates, Deborah Fish and Kim Lathan