Solar panels on the roof work, but they are expensive. Fortunately, there are portable solar panels available, which serve in an emergency and also work on camping trips. A solar panel collects electrons that the sunlight dislodges. The problem is the appliances in a home use alternating current, and need to be run at night.
The refrigerator and the freezer protect your food supply, and must be kept cold. The way around both the need for alternating current, and the need for current at night is met with a battery. The battery is charged during the day, and can operate some appliances after the sun goes down. But, not any battery will do. You need a battery that has a converter from direct current to alternating current. In fact, you would run your appliances through the battery in the day as well, even while the solar panel charges the battery.
Why would you use the battery in the day? A solar panel operates while the sun is out, but one cloud temporarily cuts it off. You do not need appliances turning on and off in short time spans. The battery keeps the power on while the solar panel is not converting sunlight into electricity. The appliances operate smoothly because of the battery. And, the power can be converted to alternating current if the battery is properly chosen.
This will not run your entire house, but will keep the critical appliances operating. In fact, my backup battery has a problem with operating anything with a battery, so your computer might not be a good thing to connect to your backup battery. Check your particular system limitations. Buy a kit and know you have all the needed parts.