Choosing the Right Generator

Because of the reasons listed above, I’m planning to upgrade to at least a 5,000-watt gasoline generator. Unless you have particularly frugal power requirements, you’ll find this to be a good basic size. But there’s still more to know before you buy.

Watt’s up with start-up?

Any appliance with a motor – a refrigerator, circular saw, drill, water pump or furnace blower – creates what’s called an “inductive” electrical load. This means energy demand skyrockets for the first second or two after start-up. You should allow two or three times as many watts for start-up compared to watts required while running. Heating elements (in stoves, toasters or space heaters), lights and small motors don’t draw significantly more current on start-up. In cases where no wattage consumption figure is stamped on an item, use the formula: volts x amps = watts. You’ll almost certainly find volt and amp numbers stamped somewhere on an appliance.

As you do the math, you may discover that you want more than 5,000 watts of backup power. If that’s the case, you should consider a stationary generator wired directly into your home’s electrical system. These units are covered by weatherproof shrouds and are ready to kick in either manually or automatically whenever the power goes off. Stationary units cost more than portables, but they deliver more power. Prices for units large enough to run multiple appliances and lights during a blackout range from about $3,000 to more than $10,000.

A dirty little secret

The quality of power is important, too. Most generators create a specific frequency of alternating current (AC) by precisely governing motor speed – or at least they try to. But in reality, governor engine control is mechanical and pretty crude, especially on cheaper generators. That’s one reason generators typically produce such dirty (irregular) and potentially damaging AC power, filled with lots of high-voltage spikes (see “Pure Power” on Page XX). But the latest generation of “clean power” generators, often called inverters, takes a different approach.

These generators have a fuel economy feature that tailors engine output speed to electrical load demanded. Traditional generators run full blast, regardless of how much power you need. The engines on today’s best generators run only as fast as needed to create the power required. Switch on a light bulb, for instance, and the motor speeds up slightly from an idle. Plug in a 1,500-watt hot plate, and motor speed increases further to meet the electrical demand. It’s a smooth, quiet and economical system that’s easier on the environment. It also significantly reduces noise output.