A fuel-powered device that can supply electricity to your house during power outages is referred to as a home generator. There are two main types of generators: permanently installed or standby generators, and gasoline-powered or portable generators.
For a long term emergency one should consider standby generators. They typically operate on natural gas or liquid propane. A fixed standby generator is already connected to both the house wiring and the fuel source. Therefore, it can start immediately either by push of a button or automatically depending on the setting. Automatic systems include an auto transfer switch. It can sense a power outage, isolate your electrical wiring or designated emergency circuits from the grid, and start up the device. When grid voltage is restored, such a system will connect you back to the utility lines and will turn itself off. Permanently connected standby systems offer power levels higher than portables.
Gasoline-powered, portable generators are typically smaller in size and power capacity than permanently installed generators. They are designed so that corded electrical devices may be plugged directly into them. Portable gas models are relatively cheap.
Aside from wattage and cost, other things to consider are the duration of time you may need emergency power, fuel availability, and convenience of use.
Portable and standby generators produce dangerous carbon monoxide (CO) gas, which can be deadly if inhaled. Detectors should be installed in case CO is accidentally released into the home