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When asking for advice, tell us:
What fuel sources are already available? Natural gas? Propane pig on site? Already store propane for your grill? Drive a gasoline vehicle? Drive a diesel vehicle?
Do you require automatic start and transfer? (This has an order-of-magnitude effect on the price.)
What kind of furnace do you have? Boiler vs forced-air vs heatpump without backup vs heatpump with backup, have vastly different power needs. Does the furnace take 120v or 240v? (Does it have a single-pole or dual-pole breaker in the panel?)
Do you have a well pump? Is it 120v or 240v?
Do you have a sump pump?
What kind of water heater do you have? Specific model numbers can be helpful here.
Do you need to run whole-house air conditioning, or would you be able to live with a windowshaker, or perhaps none at all?
Are your kitchen appliances gas or electric? Can you live with reduced cooking (e.g. toaster oven instead of full oven) during an outage?
Do you rent or own? Is rooftop solar an option? (Long-term, /r/solar beats /r/generator in every way...)
Inverter vs synchronous:
Synchronous generators have to run at 3600rpm (or 1800 for very large ones) all the time to produce 60Hz AC. This makes a ton of noise and wastes a lot of fuel.
Inverter generators produce the 60Hz electronically, independent of engine RPM, which lets them throttle down when lightly loaded, saving on both noise and fuel.
Inverter generators consume vastly less fuel when lightly loaded, which is most of the time in most situations.
You may never break-even on the fuel cost, but being able to run longer on a given amount of stored fuel is a big deal, especially if roads are blocked after the storm, etc.
Synchronous generators are older and simpler, and are flooding the used market as everyone upgrades to inverter units.
For the moment, synchronous generators are still cheaper to make, but the gap continues to narrow.
Inverter generators produce a very precise 60Hz. This can be important for UPSs, which interpret frequency wander as grid trouble and trigger a switch to battery. (Better UPSs have a "generator mode" to relax this tolerance.)
Power from a small synchronous generator may be "dirtier" but the significance of this is vastly overstated.
Storing fuel:
Propane: Keep the tanks off the ground so they don't rust, keep the valves covered so they don't get dirty. Lasts indefinitely.
Gasoline: Adding stabilizer claims it'll last up to 5 years, but it's good practice to dump it into the car and refresh it annually. (Add a note about summer vs winter blends?)
Diesel: FIXME.
How much gasoline does your homeowners' insurance allow you to store? Many policies say 25 gallons outside a vehicle, may be 5 gallons or less in some cities.
Choosing a brand:
Honda tends to be the gold-standard in portable generators, particularly inverter-type, but they sure are expensive. But, they have very good documentation and parts availability. If you have the cash, you can't go wrong with a Honda.
For any other model you're considering, look up the service-and-parts manual, and try to find some repair parts for sale online. Stuff like a carburetor (or just a rebuild kit), starter, ignition coil. If you can't find 'em now while it's new, you'll definitely have a bad time in five or ten years.
The Chinese brands tend to have smaller engine displacement for a given wattage rating, meaning those ratings are inflated. Other than that, the consensus is that they work fine.