Many smart devices have built-in battery packs, with modern laptops packing enough cells to last a whole day. However, typical desktop computers, routers, and similar devices still need to be plugged into a power source all the time to work. That's where an uninterruptible power supply (UPS) comes in. Its main function is to. Our pick for the best UPS overall goes to the APC BR1500G Backup Battery. At 1500VA/865W, it can power most devices, including computers, external hard drives, and wireless routers, from. If you need a UPS and don't want to spend a lot, the APC UPS BE425M Battery Backupis for you. Its 425VA/225W power won't keep your desktop. The Amazon Basics Standby UPSis great for those who want a UPS compact enough to fit in a small space but packs decent power for their. Most laptops have a long enough battery life to last anywhere from a few hours to an entire day. So, if you don't have a larger, more power-hungry desktop, you only need a smaller UPS.