Power
Portable generator safety and sizing
How to size a generator, and why carbon monoxide, not ER injuries, is the main danger.
Photo: smartins20 / Unsplash
NEISS recorded an estimated 4,834 ER visits involving generators in 2025. The most common diagnoses were anoxia and other. The bigger danger does not show up well in these figures, though. CPSC estimates that portable generators cause roughly 85 to 100 carbon monoxide deaths a year in the US.
Rules that save lives
- Run a generator only outdoors, at least 20 feet from the house, with the exhaust pointing away from doors, windows and vents.
- Never run one in a garage, basement or crawl space, even with the door open.
- Fit battery-powered CO alarms on every level of the home.
- Connect to house wiring only through a transfer switch installed by an electrician. Backfeeding can kill utility workers.
Sizing
Add the running watts of everything you want to power at the same time, then add the biggest single starting surge. The calculator above does this and adds a 20% margin.
Full data: Portable generators · Extension cord voltage drop.