How to choose a UPS for your router and computer during a power cut

A UPS (uninterruptible power supply) can keep selected equipment powered when the mains supply fails and, depending on the model, help protect it against electrical problems. But choosing one does not start with comparing the biggest numbers on the box. It starts with deciding what must stay on and what task you need to finish. A router with an ONT or modem may be enough to preserve your internet connection; adding a computer, monitor and peripherals increases the load and reduces the available runtime margin. Vertiv’s selection guide likewise starts from load requirements and the backup needed, rather than relying only on a product category name (Vertiv guide).

Describe your goal as a specific situation: for example, finishing a call, saving your documents and shutting down the computer properly, or keeping connectivity during a short outage. These are not equivalent goals. The duration you want to cover depends on which devices you connect to battery-backed outlets, how much power they are drawing at the time, and how the UPS behaves with that load. Do not choose runtime by intuition or assume that a published figure applies to your installation.

Make an inventory before looking at models. List every device you want to power, its power adapter or cable, and whether it needs to remain active throughout the interruption. Include the ONT or modem if it is separate from the router: keeping the router on alone does not guarantee that the external connection remains available. Also identify which devices can be switched off immediately and which need enough time to save work. This list defines the job the UPS must do and makes it easier to assess whether a proposed model is suitable, instead of treating every device in the room as an automatic candidate for backup power.

Check each device’s label, power adapter or manufacturer documentation for its power consumption or input rating. Add the values for the equipment you will actually connect to the UPS, then compare the total with the model’s specified maximum output power. The important figure is not only capacity in volt-amperes (VA): you also need to check how many watts (W) it can supply. Vertiv includes load capacity among the factors to evaluate when selecting a unit (Vertiv guide).

VA and W describe related, but not interchangeable, aspects of electrical capacity. The power factor relates the two quantities, so do not convert a VA rating to watts on the assumption that they are equal. The product specification should state both limits or provide the information needed to assess them. The connected load must stay within the W limit and the VA limit, as well as any other restrictions given by the manufacturer. If you compare only VA, you could assume that two models support the same load even though their wattage limits differ.

Adding rated power values is a useful first check, not an exact measurement of what the devices will draw at every moment. A computer’s consumption can change with its workload, and peripherals and adapters can contribute as well. Keep a reasonable margin below the published maximum and avoid planning a load that sits right at the limit. If you cannot determine actual consumption, or a label is ambiguous, consult the device documentation or manufacturer rather than assigning an estimated value and treating it as a measured fact. Where equipment has different operating modes, use information that reflects the situation you need to cover, while still respecting the UPS’s stated limits.

Runtime indicates how long a UPS can support a load from its battery under particular conditions. It is not a fixed property that can be inferred from the VA label, nor a promise that applies to every combination of devices. Vertiv provides a runtime calculator, and APC publishes backup-time tables for specific configurations; both kinds of resource illustrate why runtime must be considered in relation to the model and the load (Vertiv tool; APC table for Galaxy VS).

When comparing figures, identify the load each estimate refers to and check which battery or configuration it assumes. A table for an enterprise-grade unit such as Galaxy VS cannot be used to infer the runtime of a different household UPS. Nor should you transfer a figure from one model to another just because both have the same VA rating. Use the curves, tables or official selectors for the model you are considering whenever they are available. APC, for example, provides a UPS selector to help guide customers through choosing its equipment (APC UPS Selector).

Actual runtime can vary with the load and battery condition, among other factors. Manufacturer selection resources are useful for comparing units under stated conditions, but they cannot establish how long a particular installation will run without information about that installation. Treat a published runtime as a reference estimate associated with specific conditions, not as a universal guarantee. If your priority is keeping connectivity for as long as possible, assess the router and ONT consumption separately. You may not need to power the computer for the entire outage as well. Consider the task you need to complete, the devices involved and the order in which you could shut them down; those decisions affect which runtime estimate is relevant to your needs.

Count the outlets you need and check which ones receive battery power during an outage and which provide surge protection only, if the model distinguishes between those groups. Check the physical plug type and rated voltage too: a specification sheet for the US market, for example, may list NEMA outlets and 120 V, which may not match another country’s installation. The APC Back-UPS Pro BR1500G is listed on the manufacturer’s website as a 1500 VA, 865 W, 120 V unit with ten NEMA 5-15R outlets. Those details describe that product and market, not a general UPS specification (APC product page).

Do not automatically connect every device you happen to have. A laser printer, heater or other high-power device could exceed capacity or be unsuitable for battery-backed outlets; check the instructions from both manufacturers. For a typical connectivity and remote-work setup, prioritise the devices needed for the goal you have defined and leave outlets unused if you do not need them. Extra outlets are valuable only if their plugs are compatible and they provide the function you require. Check whether the number advertised counts all outlets or only those with battery backup, and do not rely on a product photograph in place of the outlet descriptions in the specification.

Check whether the model offers surge protection, automatic voltage regulation (AVR), alarms, a display or communication ports. Do not assume that an advertised feature protects against every kind of electrical disturbance, or that all outlets have the same function. Read the description of each outlet group, the electrical limits and the warnings in the specification. If the manufacturer separates battery-backed outlets from surge-protected outlets without backup, plan your connections accordingly. The distinction matters: a device plugged into a protected-only outlet may lose power during an outage even though the UPS itself has a battery.

Manufacturers sell several UPS topologies, including standby, line-interactive and online systems. The choice depends on the connected equipment, the electrical behaviour you need and your budget; there is no rule that makes one topology best for every home. Vertiv’s buying guide lists topology among the selection factors that should be considered in relation to the installation’s needs (Vertiv buying guide).

For a router and computer, start by checking the actual specifications: output power, estimated runtime, output waveform, transfer time where stated, and declared compatibility. Do not infer performance solely from marketing terms such as “online” or “line-interactive”. If a computer has a power supply with particular requirements, confirm compatibility with its manufacturer or the UPS documentation. The sources consulted do not provide an independent comparative test that would justify declaring one topology superior for every remote-work setup. Match the specifications to your devices and intended use rather than treating a topology name as a substitute for checking them.

IEC 62040-3:2021 covers methods for specifying performance and test requirements for UPS systems. It is a reference for interpreting specifications, not an automatic guarantee that any particular unit will solve your situation. The available bibliographic record describes the standard’s scope (IEC 62040-3:2021). Check what the manufacturer says about conformity and which configuration was tested; do not interpret a bare reference to a standard as independent verification of every marketing claim. A standard can help you understand how declared performance is framed, but the model’s own documentation remains essential when you need to establish its limits and suitability.

The battery is a service component, not a minor detail. Check whether the model allows battery replacement, whether a replacement is available in your market, what procedure the manufacturer specifies, and whether replacement affects the warranty. For example, APC’s product page identifies the BR1500G as a model with a user-replaceable battery; that feature cannot be attributed to every UPS (APC BR1500G).

Placement matters too. Follow instructions on ventilation, temperature, grounding and distance from heat sources. Put the unit on a suitable surface and do not cover its ventilation openings. Read the specific instructions before connecting the UPS to another protective device or a power strip, since manufacturers do not all permit every combination. If you are unsure how to connect the equipment safely, seek qualified guidance. Do not improvise connections to increase the number of outlets or assume that a surge protector can be combined with any UPS without checking the instructions.

Look into the warranty for the UPS and the battery separately if the manufacturer specifies different terms. Also check replacement availability and the options for recycling or returning used batteries in your area. Information may vary by country and product reference, so a page for another region is not enough to confirm local coverage. Include the cost and ease of maintenance in your comparison: a model that costs less initially may not be the best choice if you cannot obtain a compatible battery when you need one. Ask whether the replacement part is intended for the exact model and whether the manufacturer describes a user procedure or requires service support.

Before completing a purchase, verify the exact model and regional variant in the manufacturer’s documentation. Do not combine specifications from products that merely have similar names: differences in voltage, plug type, power, outlet count or replacement-part availability can change whether a unit is suitable. A US specification sheet, such as those for the APC models cited here, describes products rated for 120 V. Use it as an example of what to check, not as a buying recommendation for other markets.

Put the information together in a list and rule out models that fail any essential requirement. For runtime, look for a table or tool that identifies the model and load; if the conditions behind an advertised figure are not available, do not treat it as directly comparable. For consumption, distinguish W from VA and respect both limits. For outlets, count only those that provide the function you need. The right choice is the one that supports a defined load with verifiable specifications, not necessarily the one with the biggest number on the box. Keep a note of the source for each key figure so you can compare like with like instead of relying on product names or headline capacity alone.

A final check can follow this order: 1) define which devices must stay active and the backup objective; 2) find and add their input power ratings; 3) verify the UPS limits in W and VA; 4) estimate runtime using model-specific information and a comparable load; 5) confirm outlets, voltage, replaceable battery and support in your market; 6) review installation, warranty and battery handling. If key information is missing, ask the manufacturer for clarification before buying rather than covering uncertainty with an assumed figure. This sequence keeps the decision tied to your actual use, helps expose regional mismatches and makes it easier to explain why a model does—or does not—meet your requirements.