What should you not plug into a generator?

Sensitive electronics, sump pumps running at or near a generator's peak watt limit, and appliances with variable-speed motors are the most critical things to avoid plugging directly into an open-frame portable generator. Medical equipment, laptops, and CPAP machines are also high-risk.

Open-frame portable generators — including DuroStar's DS and MX series — typically produce total harmonic distortion (THD) of 12% or higher. Sensitive electronics require THD under 5% to operate safely; anything above that risks damaging internal components over time. A refrigerator or well pump is fine on a DuroStar generator because motors tolerate voltage variation. A laptop plugged in directly is not — run it through a UPS or battery inverter instead. Medical devices like CPAP machines fall into the same high-risk category.

• Open-frame DuroStar generators produce THD of approximately 12% or higher — unsafe for sensitive electronics requiring under 5% THD.
• Inverter generators deliver under 3% THD; open-frame DuroStar models are not inverter generators.
• A 3-ton central AC compressor draws a startup surge of 4,500–5,500W; plugging one into an undersized generator risks engine bog or breaker trip.
• Medical equipment (CPAP, home oxygen concentrators) should never connect directly to an open-frame generator without a UPS or pure-sine inverter buffer.
• Natural gas or propane output on DuroStar dual-fuel models runs approximately 5% lower than gasoline — relevant when calculating whether a load is within safe operating range.