Popular Mechanics (USA)



EXTREME WEATHER—LIKE THE COLD snap that took down the power grid in Texas, heat waves that spiked demand and caused rolling blackouts in California, and more severe hurricanes that have been strafing the East Coast from Florida to New England—is increasing­ly making backup power a priority. A good generator can run appliances such as refrigerat­ors, freezers, sump pumps, well pumps, and chargers for laptops and mobile devices, protecting our food and belongings as well as keeping us connected to the larger world during natural disasters and emergencie­s.

Today, for many people with laptops and phones to charge and smart appliances, home-theater systems, sound systems, or other sensitive electronic­s to power, whether during a blackout or while tailgating or camping, the best option will be an inverter generator. Consider the main advantage over their non-inverter cousins: These generators provide clean power for modern electronic devices, many of which are susceptibl­e to fluctuatio­ns in electrical current. That “clean” power is 120 volts of alternatin­g current (AC) at a frequency of 60 Hertz (Hz), the same you’d get from a typical wall outlet. The electrons flowing through wires carrying AC change direction at regular intervals, with 60Hz indicating that the current does this 60 times in one second. Visually, the frequency of the alternatio­n of the current looks like a perfect sine wave.

Most commercial­ly available non-inverter portable generators produce 120 volts of AC at 60Hz. However, many appliances require more power to start up. This initial load requires generators to boost the current to meet the demand. Because the generator must first sense this voltage draw, there’s a lag before it increases the current to the device. This delay can cause both the voltage and frequency from the generator to dip before returning to steady states. Again, represente­d as a sine wave, the individual peaks and valleys will appear asymmetric­al, and the measuremen­t of the deviation from a pure sine wave is called Total Harmonic Distortion (THD). Too much THD can jack up both the voltage and current and increase heat in components on circuit boards, which in the extreme can damage them and also shorten their life spans. Decreases, on the other hand, may be passed through circuits, causing malfunctio­ns.

You’ll see THD listed in most generator specs as a percentage. The Institute of Electrical and Electronic­s Engineers (IEEE) says that power systems for computers and related electronic­s and equipment should have no more than 5 percent THD. And there’s the rub: Traditiona­l generators may have THD as high as 15 or 20 percent. Inverter generators produce AC power as well, but they convert it to direct current (DC) and then back to AC before it can be used to power anything. DC current is very stable, flowing constantly in one direction. So the conversion of AC to DC acts like a filter, and the inversion back to AC yields a THD that is typically very low.

Other benefits include their closed-frame design, in which the engines are fully encased, making them much quieter than traditiona­l generators. And most models have an economy mode that reduces engine RPM when there are low loads on them, boosting the lifespan and efficiency. Their engines are also set to run at lower RPM in general, and due to the stabilizin­g nature of the conversion and inversion from AC to DC and back to AC, they don’t labor as much to meet increased demand. To size one correctly, you still need to calculate and account for the start-up loads of larger appliances and tools. But if you’re charging mobile devices, using computers, modems, or sound equipment, or powering smart appliances, an inverter generator is the best choice to prevent potential (and, likely, expensive) damage to your gadgets.

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