The proposed solutions are nice but you can do something workable for much less money. My solution, which I've implemented, involves more work when the power fails but saves a lot of money.
All you really need to power are the furnace blower and fridge, and they need power only part of the time. You can use LED flashlights for light and a battery powered or 12V DC TV and radio.
For perhaps $100 you can get a 700W inverter that clips into your car battery and provides about 5 amps. That will run a small TV and your computer. You can get smaller inverters for less money. These inverters will not power serious motors, such as probably, your furnace blower. Indeed, they may damage a motor that uses them.
Details: These inverters produce a seriously non-sine wave with about 30% harmonics. The harmonics turn into heat in the motor. Also the inverter may not be able to supply the startup current, which might be over 3x the running current.
Another problem with inverters is that their non-sine wave is said to be bad for small AC-DC power supplies for battery chargers etc. I have not explored the meaning of "bad" since I have no spare power supplies to destroy.
To power my furnace blower, I got a 2000W Honda generator for about $900. Note that the 2000W is a shorttime load, the continuous load is a lot smaller. The Honda, unlike cheaper generators produces a true sine wave. It can also supply a large starting current.
I paid an electrician to change my furnace from hardwired to plug in. So, if there's a power failure, I unplug the furnace from the wall and plug it into my generator, which I would run outside the house.
Advantage of my solution: It costs $1200 and I have a portable generator and inverters I could take other places.
Disadvantages: It's not automatic; I have to refill the generator, etc. etc.