Pure sine wave

Pure sine wave describes the shape of the AC power an inverter produces, and it closely mirrors the smooth waveform that comes from the electrical grid or a campground pedestal. Modified sine wave inverters produce a rougher, stepped approximation of that waveform, which costs less to build but is not identical to grid power.

Most modern electronics, including laptops, phone chargers, and anything with a variable-speed motor or sensitive control board, run more reliably and run cooler on pure sine wave. Some devices, like certain CPAP machines or audio equipment, can hum, run poorly, or refuse to charge properly on modified sine wave.

The mistake to avoid is buying a modified sine wave inverter to save money and then discovering a key device does not tolerate it well. Checking the manual for any appliance that seems finicky about power quality, before assuming the inverter itself is faulty, saves a lot of troubleshooting.