A prolonged power outage can be inconvenient, costly, and (possibly) dangerous. Food in refrigerators and freezers can spoil. Loss of heat can be uncomfortable at best and deadly in the worst case. If critical medical equipment cannot operate then an outage could be deadly. Power outages often happen due to severe weather, extreme cold, or overburdened electrical grids.
Power outages often happen during winter storms. Damaged power lines often cause the outages. Gas heaters probably need electricity to run the HVAC system. Be sure to have sleeping bags and/or blankets that can keep you warm if the house temperature falls. If the outage last for several days then the inside temperature could approach the temperature outside. You may be able to use propane heaters indoors but be sure to only use appliances rated for indoor use. Also note that these indoor heaters still require venting.
A generator can supply electrical power to your home when the power fails. Generators normally connect to a dedicated breaker in your electrical box. Electricity flows from the generator into the breaker and then to circuits in the house. You must isolate the income electrical main from the power created by your generator.
An incorrect generator installation could cause injury to death to utility workers. The easiest installation requires dedicated breakers for the generator, and outside generator outlet, and an interlock installed on the breaker box. The interlock is a simple, physical plate that isolates the outside electrical main from the power created by the generator. If the main electrical supply (from the street) is ON then you cannot activate the generator breakers. If the generator breakers are ON then then the main power breakers MUST be OFF. Be sure to get an electrical permit and inspection when installing a generator.
Before purchasing a generator calculate the amount of wattage needed. A generator guy at our local hardware store (a real store, not a big box store) told me that you want to properly size your generator. If the generator is too small, then it cannot generate the required power and that will severely shorten its life. If the generator is too large and there is not enough load then that is also not good. You want the generator to work at an optimal level (not too easy or too hard).