Key Facts: Portable Generators
This page is Generator Decoded's maintained fact reference — the sizing and noise facts our guides are built on, restated in plain prose. We report published specifications and documented engineering methods, never a claim that we personally tested a unit.
Running watts vs starting watts
A generator's headline number is almost always starting (surge) watts — the brief spike a motor draws for a fraction of a second at power-on. The number that limits what you can run all day is the smaller running (rated) watts figure. Motor-driven appliances (fridges, well pumps, sump pumps, air conditioners, furnace blowers, shop tools) surge roughly 2-4x their running draw; purely resistive loads (lights, most microwaves, chargers) barely surge at all. Full breakdown and appliance-by-appliance numbers: Running vs Starting Watts and the Startup Watt Index.
Central air conditioners and LRA
Central AC is the hardest common appliance to size for because its surge isn't a fixed ratio — it depends on the compressor's LRA (Locked Rotor Amps), printed on the unit's data plate. Estimate starting watts as LRA × voltage × a ~1.2 safety margin; a 60A LRA compressor at 240V needs roughly 17,000 surge watts, far beyond most portable generators. Details in What Size Generator for Central AC?.
Noise ratings are measured at inconsistent distances
An informal industry norm uses 23 feet (7 meters) as a comparison distance for generator dB(A) claims, but it is not an enforced standard. Sound intensity falls under the inverse-square law — moving twice as far away drops perceived loudness by about 6 dB — so a dB(A) number without a stated test distance cannot be fairly compared to one that states 23 ft. Many popular models (WEN, DuroMax, Generac, Champion, Predator in our review) do not consistently publish a test distance at all. Full explanation and normalized numbers: Why Generator dB Ratings Don't Match and the Generator Noise Normalization Index.
Inverter vs conventional generators
Inverter generators produce a cleaner sine wave (safer for sensitive electronics) and are commonly tested for noise at 25% load — their quietest point — while conventional generators are often tested at 50% load. That testing-convention difference, on top of the distance problem, is another reason two dB(A) numbers can look similar on paper and sound very different in a yard. More in Is an Inverter Generator Quieter?.
Carbon monoxide safety
Every gasoline generator produces carbon monoxide, an odorless gas that can be fatal in minutes. It must run outdoors, well away from windows, doors, and vents, and never in a garage even with the door open — this is a documented, recurring cause of accidental death during power outages. Always follow your unit's owner's manual for exact placement and consider a battery-powered CO detector regardless of where the generator sits. See How Far Should a Generator Be From a House?.
How these facts are maintained
These facts are drawn from manufacturer spec sheets, published generator-sizing references (Jackery, Renogy, ALLPOWERS, generatorsizer.com, HVAC-Talk, Mike Holt electrical forums), and the documented physics of LRA sizing and inverse-square sound attenuation, reviewed against our guides and updated on the date shown above when specs or the market change. We do not publish prices or star ratings, every pick names an honest drawback, and we never claim to have load-tested or sound-tested a unit ourselves. Full methodology: How We Evaluate.