Three percent on the label

Many generator labels list a figure for total harmonic distortion, and on some it reads under

three percent. That small number explains why an inverter generator can run a furnace control

board or a laptop charger that a basic machine might upset, which matters as fall storms begin

knocking out power across Canada and outages stretch into the colder months.

The electricity is made twice

A conventional generator's alternator produces household current directly, so the engine has to

spin at a fixed speed to hold the frequency steady. Any wobble in engine speed or any sudden

load shows up as a ragged waveform at the outlet.

An inverter design does something that sounds wasteful. Its alternator produces rough, high-

frequency current, which electronics convert to direct current and then rebuild into a smooth

alternating wave at the correct frequency. The engine is no longer responsible for the shape of

the power, only for the quantity.

Distortion describes how far a waveform strays from a smooth curve, the extra ripples riding on

top of it. Motors fed a distorted supply run warmer, and electronic controls such as the variable-

speed blower in a modern furnace can misread it and shut down. A low figure means the supply

looks much like utility power to those devices.

Why does the engine slow down?

Because frequency now comes from the electronics, the engine can change speed to match

demand. With only a refrigerator and a few lights connected, it idles down, burns less fuel and

makes far less noise, which is why an inverter is often the practical answer for anyone looking

for a quiet generator near a house.

When a large load such as a well pump starts, the engine speeds up to supply it, and the output

waveform stays clean throughout. Motors draw a brief surge several times their running current

as they start, so an inverter generator has to be sized for that starting surge rather than for the

pump's running rating alone.

How a dual fuel inverter generator behaves in a Canadian winter

It runs on gasoline or propane, and the choice changes how it behaves. Gasoline carries more

energy, so output is usually higher on it, but stored gasoline goes stale within months unless it is

treated.

Propane keeps indefinitely in its cylinder, which suits a machine that may sit unused until an ice

storm. Its weakness is cold. The pressure inside a propane cylinder falls as temperatures drop,

and in a deep freeze a small cylinder may struggle to deliver fuel as fast as a heavily loaded

engine wants it. A larger cylinder vaporizes fuel more readily in the cold, and cylinders should

never be warmed with a flame or heater.

Connecting to the house is the dangerous part

An inverter generator for home backup should never be plugged into a household outlet to feed

the wiring backward. That current can travel out onto the utility lines and injure the crews

working to restore power. A transfer switch or interlock installed by a licensed electrician keeps

the house isolated from the grid.

Exhaust matters as much. Generators belong outdoors, well away from windows, doors and

vents, since carbon monoxide builds up quickly in garages and sheds. A home generator used

this way, such as the 7250 watt dual fuel inverter generator from TMG Industrial with its low

distortion rating, can carry essential circuits through a long outage when it is placed and

connected this way.