Computer Uninterruptible Power Supply Units

Add the wattage of your computer, monitor(s), router, and other devices, then choose a UPS with continuous output wattage at least 20–25% higher than that total; also check the VA rating and aim for a UPS whose VA-to-watt ratio matches the device power factor (commonly 0.6–0.9 for consumer gear)

Runtime depends on UPS capacity and connected load: smaller desktop UPS units often provide 5–20 minutes at typical PC loads, while larger models or external battery packs can provide 30 minutes to several hours; manufacturers list runtimes at specific load percentages so compare those figures for your estimated wattage

Standby (offline) is suitable for basic surge protection and short outages, line-interactive adds automatic voltage regulation for brownouts and overvoltages, and online (double-conversion) provides the cleanest, continuous power with no transfer time and is recommended for sensitive or mission-critical equipment

UPS batteries are consumables typically lasting 3–5 years; look for models with user-replaceable hot-swappable batteries, check the manufacturer’s battery type (usually sealed lead-acid or lithium), and plan periodic battery tests and replacements to maintain runtime and reliability

Ensure the UPS has enough battery-backed outlets for devices you need protected and isolated surge-only outlets if required; consider USB/serial/Ethernet/USB-C communication, network management cards or software for graceful shutdown, and features like AVR, LCD status display, and alarm control based on your use case

Choose tower for desktop placement, rackmount for server cabinets (often convertible between tower and rack), and verify physical dimensions, weight, ventilation clearance, and the presence of rack ears or rails if you plan to install in a 19-inch rack

Check output waveform (pure sine wave preferred for active PFC power supplies), surge protection rating (joules), transfer time, VA and watt ratings, battery chemistry, certifications (e.g., IEC, UL), and warranty terms to evaluate safety and expected performance