Safety notes & disclaimer
Safety first.
- Never backfeed a generator by plugging it into a wall outlet. It can electrocute utility line workers and neighbors and bypasses your home's protection (CPSC).
- Connecting any generator or battery to house wiring requires a transfer switch or listed interlock installed by a licensed electrician, with permits where your city or county requires them.
- Carbon monoxide kills. Run portable generators outside only, at least 20 feet from the house, exhaust pointed away, never in a garage, basement, shed or porch. Install battery-backed CO alarms (CPSC).
- Planning estimates only. Results are planning estimates, not engineering advice, electrical design, or a substitute for a load calculation by a licensed electrician (for example, a National Electrical Code load calculation). Have a licensed electrician confirm sizing, wiring and any transfer switch before you buy or install. Follow your equipment manuals and local code.
Generators
- Never backfeed. Don't plug a generator into a wall outlet or dryer receptacle with a double-ended ("suicide") cord. It can energize utility lines and kill line workers, and it bypasses your home's protection.
- Carbon monoxide. CPSC reports about 85 consumer deaths a year from portable-generator carbon monoxide poisoning (CPSC, 2022). Operate outdoors only, at least 20 feet from the house, with exhaust pointed away from windows, doors and vents. Never in a garage, even with the door open. Install battery-backed CO alarms on every level.
- Fuel. Let the engine cool before refueling. Store fuel in approved containers away from living spaces and ignition sources.
- Keep the generator dry and use outdoor-rated, heavy-gauge extension cords sized for the load.
Batteries and power stations
- Use only the manufacturer's chargers and accessories, and follow its placement, ventilation and temperature limits.
- A battery tied into house wiring also needs a proper transfer switch, gateway, or interlock installed by a licensed electrician.
Disclaimer
Everything on BackupEngineer, including the calculator and the guides, is general education. It is not electrical design, engineering, or professional advice for your home, and it does not create any professional relationship. Wattages vary by model and the defaults are approximate planning figures. Your equipment's nameplate and manuals, your local electrical code, your utility's rules, and a licensed electrician's judgment always take priority. You use this site at your own risk; we make no warranty that any estimate is suitable for your situation.