With the grid about to become more unreliable, you will need a battery-backup system to continue working when it goes off, or at least to shut down the computer safely until the power comes back on.
Laptop computers use far less energy than desktop computers. A desktop can often require several hundred watts (especially if you have a power-hungry graphics card), while a laptop can often use as little as 40W during normal operation. Laptops are designed to be energy misers so that they can run longer off their internal battery.
Speaking of internal batteries, you will want to purchase extra ones in case they become difficult to get.
Keeping Data Safe
Hard drives, being mechanical devices, will break down and take your data with them. A system that uses multiple drives will make sure that when one drive fails the data is not lost. You will need to purchase extra hard drives for that system to work. If you'd like the data to be available from anywhere on your home network, purchase the network sharing attachment.