Most US 1960s era homes were wired with what's called "100 Amp" service, although that's about when "150 Amp" began to be used fairly often and "200 Amp" might be wired for a larger home.

A "100 Amp" service means that the line coming into the house can supply up to 100 Amperes at 220 Volts, or a maximum total of about 22 KW (22,000 W) to what's plugged in inside.

For a true "standby generator" this is what you'd need to just "flip a switch" and continue business as usual when the utility line goes down.

In most places, construction codes would require that the generator be placed on a separate (usually concrete) "pad" outside the house, with appropriate fuel storage/connections.

This is the $15,000 - $25,000 installation, but is almost certainly more than needed.

ANY GENERATOR SYSTEM MUST BE ISOLATED from the outside power company connection any time the generator is used. Building codes vary, but in many places an "automatic switch" (interlock) is required that disconnects the house COMPLETELY from the outside power lines before the generator can be started. For a more modest "emergency generator" you may be able to disconnect from the line just by flipping a "master breaker" off, but you will need to check on local codes to be sure that you provide an acceptable (and reliable) "disconnect" for any system you install. If you use a "manual" disconnect, you need to be certain that anyone who might try to turn on your generator will follow the instructions correctly every time.

To get an idea of how large a generator you need, you really need to search out the "ratings plates" on all of the things that you need to keep running. Most of the things you've named will be 120 Volt devices, so you can just add up the "Ampere" ratings from all the rating plates, multiply the total Amps by 120, and you'll have the "watts" you need.

The $300 to $500 generators generally run from around 2,000 Watt (2 KW) up to about 7,500 Watt (7.5 KW). One of these should be sufficient to keep the heating systems running, and at the top end might also run the refrigerator and freezers; but you'll need to add up the amps for the devices you consider "necessary" in order to know what you really need.

Most electric stoves are 220 Volt 50 Amp devices (11 KW) so you're unlikely to be able to run one on any modestly priced generator. Perhaps a propane "grill" on the patio would be an option(?).

With home wiring, an additional problem you'll have will be turning OFF the things you don't need to run during the outage. With luck, the essential devices will be on separate breakers, so once the breaker panel is disconnected from the outside world, if that breaker panel is connected to the generator, you can just turn off all the breakers that aren't needed. The burden here is knowing which ones have to be left on. Installing a separate "emergency panel" that connects only to the essential devices (and to the generator) would be a preferred solution; but may be somewhat expensive and may require some re-wiring, of the existing panel and of the critical circuits, to permit isolation of the circuits you need.

It should be noted that small electric generators are not particularly efficient; and fuel costs alone to keep one running continuously for a few days may come close to the cost of a motel if you can find a "budget" motel that can be relied on. Putting the purchase and installation cost into a separate "emergency" bank account to pay the motel bills might be a viable option.

John