Propane standby generators are great if the cost doesnt scare you. Since you already burn fuel oil for heat, maybe you can find a diesel standby generator.

Battery banks are expensive. As is solar. This is an investment, and understanding the life span of batteries is also very important before you make a decision. If you go this route do some research on grants related to renewable energy.

The cheapest option is a portable generator, which can also be powered by propane, and a transfer switch.

For the amount of times we lose power a year (in my rural town, i see 2 - 4 per year avg), i would just get a portable generator and be very diligent with fuel treatment, or run it on propane.