Which Smart Home Gear Needs to Run During a Power Outage?

The smart home gear to keep running during a power outage is not the whole smart home. It is the path that lets the rest of the system still know what is happening: modem, router, smart-home hub, the switch or access point those devices depend on, and only then camera or recording gear that has a real reason to stay online.

That order matters because most outages are not solved by giving every plug in the cabinet a battery. A hub without a router may still run local radios, but you lose remote access and some integrations. A camera bridge without the switch it uses is just warm plastic. A Home Assistant box without its coordinator, network, or storage path may come back in a strange mood and leave you sorting out automations after power returns.

The useful question is smaller and more testable: how many watts does the outage-critical core draw, and how many minutes or hours do you want that load to run?

Keep this path alive first

Start at the wall outlet and work forward. If the grid drops, the first UPS outlets should go to the devices that preserve the network and the smart-home brain.

1. Modem or fiber ONT: without this, internet access is gone even if your Wi-Fi is still broadcasting.
2. Router or gateway: this keeps the LAN, DHCP, firewall, and often Wi-Fi alive.
3. Smart-home hub: Home Assistant, Hubitat, SmartThings hub, HomeKit bridge hardware, or another controller that runs local automations.
4. Network switch or access point: include this only if the hub, camera bridge, PoE coordinator, or access point depends on it.
5. Camera base station, NVR, or PoE camera switch: add this when recording or security coverage is part of the outage plan.
6. Home Assistant host, NAS, or mini PC: keep it on the UPS only if it is actually part of control, logging, storage, or graceful shutdown.

Everything outside that chain has to earn its place. A TV, monitor, desktop PC, speaker system, printer, or decorative lighting load can turn a long network backup into a short demonstration. The UPS is not there to make the outage comfortable. It is there to prevent the network path from collapsing and to let the controller see, log, notify, and recover cleanly.

Why load matters more than the VA number on the box

VA rating is easy to print large. Runtime is harder, because runtime depends on the actual load. Wirecutter’s UPS testing makes the point neatly. On a small 20 W load, which is in modem-and-router territory, the tested units ran for hours or close to it. At 300 W, the same units fell to minutes.

That is the whole sizing lesson in one table. The battery that looks generous for a modem, router, and hub becomes a short bridge when it is asked to carry a workstation-class load. For a smart home, the win is not buying the biggest box by instinct. The win is keeping the load small enough that the battery has time to matter.

Build a wattage budget for your outage-critical core

The clean way to size this is to make a load list. Use a plug-in power meter if you have one. If not, planning estimates are still better than guessing from VA ratings. HomeTechHacker’s smart-home UPS guide estimates a small smart-home network at roughly 25–40 W, with common device-level ranges for modems, routers, hubs, switches, camera bases, and NAS gear; these are planning estimates, not lab measurements for your exact hardware. [2]

For the router specifically, EnergySage puts typical Wi-Fi router draw at 5–20 W and calls about 10 W a safe planning average. [3] That lines up with the practical experience of many smart-home cabinets: the router is important, but it is not usually the thing that destroys runtime. The extra switch, PoE load, NVR, or NAS is where the budget starts to grow.

A modest setup might be only a modem, router, and hub. A more serious setup may add a switch, PoE access point, camera bridge, and a Home Assistant mini PC. Those two cabinets should not be shopping from the same runtime assumption, even if both owners are looking at boxes labeled 1000 VA or 1500 VA.

A practical load worksheet

If your total lands somewhere around 25–100 W, you are in the range where UPS runtime math becomes more important than output headroom. If it lands above that, do not assume the UPS is undersized yet. Look for the device that moved from “network core” to “nice to have” without anyone noticing.

Translate watts into runtime

The basic runtime calculation is simple:

usable watt-hours ÷ load in watts = runtime in hours

The annoying part is that UPS product pages do not always make usable watt-hours obvious. Some publish runtime charts instead. Some publish battery voltage and amp-hour ratings. Some only lead with VA and watts. When you can find usable watt-hours or a runtime chart at a load near your own, use that. When you cannot, leave margin for inverter losses and do not size the purchase to the last calculated minute.

As a clearly hypothetical example, if your outage-critical core draws 40 W and a UPS could deliver 120 usable watt-hours after losses, the runtime estimate would be 120 ÷ 40, or about 3 hours. If the same UPS is carrying 80 W, that rough estimate drops to about 1.5 hours. Nothing magical happened to the UPS. The load doubled.

HomeTechHacker’s VA-tier estimates are useful as planning ranges at a 30 W smart-home load: about 40–60 minutes for 650 VA, 60–90 minutes for 850 VA, 90–120 minutes for 1000 VA, and 2–3 hours for 1500 VA. Treat those as estimates, not guarantees, because model design, battery condition, inverter behavior, and your actual load all matter. [2]

Pick a runtime target that matches real outages, not a neat average

Once the load is visible, outage statistics become useful. They are poor shopping shortcuts but good reality checks.

The U.S. Energy Information Administration reported that electricity customers averaged 11 hours of interruptions in 2024, and about 80% of that time came from major events such as Hurricanes Beryl, Helene, and Milton. The same EIA analysis noted large state differences in 2024, including about 53 hours in South Carolina and under 2 hours in Arizona. [4]

That does not mean every UPS should be sized for 11 hours. It means a national average can be dominated by major-event years. In 2022, EIA reported an average of about five and one-half hours of power interruptions per customer, while non-major-event interruptions have stayed around 2 hours since 2013. [5]

For a smart-home UPS, the target usually falls into one of three jobs: ride through short flickers and recloser events, preserve the network through a one- to two-hour local outage, or keep the core alive long enough for a storm response plan. The third job may still outgrow a normal plug-in UPS. That is not a failure of the math; it is the math telling you where the boundary is.

What belongs on the UPS, and what should stay off

Put the modem, router, and hub on first. If your hub reaches Zigbee or Z-Wave through a separate coordinator attached to a Home Assistant host, that host and coordinator belong in the same decision. If your cameras record to a base station or NVR and you actually need recordings during an outage, include that equipment and count its watts.

Be careful with PoE. One small switch can look harmless until it is feeding access points and cameras. If the PoE switch is essential, count the downstream devices too. If only one coordinator or camera needs backup, a smaller dedicated power path may be cleaner than dragging the whole switch onto the UPS.

A NAS deserves a separate decision. If it stores camera footage or hosts critical services, it may need UPS power or at least a graceful shutdown path. If it is mostly media storage, it is probably stealing runtime from devices that keep the home controllable. The same logic applies to monitors, desktops, speakers, printers, and mesh nodes that do not cover the hub or occupied part of the house during an outage.

Also remember the limit of your own outlet. A UPS can keep your local network alive, but it cannot guarantee that the ISP’s upstream equipment, cloud services, or cellular backup paths are still working. Local automations and local control are the pieces you can most directly protect.

Buying details that actually matter

After the wattage budget and runtime target are set, the shopping list gets shorter. Look for a UPS with enough output wattage for your load, runtime data near that load, automatic voltage regulation if your area has sags or unstable utility power, and user-replaceable batteries. Wirecutter also notes that replacement batteries commonly cost about $30–$60. [1]

The safety rule is not negotiable: do not plug a UPS into an extension cord or a surge protector. Wirecutter gives the same warning, and it is one of the easiest mistakes to make in a crowded network closet. [1] If the devices cannot reach the UPS directly, fix the layout instead of building a chain of power strips.

• Prefer enough battery runtime at your actual load over the largest VA number in your budget.
• Check how many battery-backed outlets the unit has; some outlets may be surge-only.
• Keep wall-wart spacing in mind, because oversized adapters can block neighboring outlets.
• Plan for battery replacement instead of treating the UPS as a one-time purchase.
• Test the setup by pulling utility power to the UPS, not by waiting for the next storm.

After the UPS is in place

Once the hardware is sized and installed, the next layer is behavior: alerts, shutdowns, and recovery checks. If you run Home Assistant or another controller that can read UPS status, the natural next step is an automation plan. The site’s power-outage smart-home automation recipe covers outage alerts, UPS status, and graceful-shutdown behavior, so this piece can stay focused on sizing.

If a storm is the reason you are doing this work, pair the UPS budget with a broader smart-home hurricane prep checklist. If the hub or devices still come back badly after power returns, use the relevant troubleshooting path rather than blaming the battery first: smart-home hub troubleshooting, Apple HomeKit hub troubleshooting, or Z-Wave smart switch troubleshooting.

The final purchase decision should come from the load list, not the front of the UPS box. Keep the modem, router, hub, and necessary network bridge alive first. Add camera or storage gear only when it serves the outage plan. Then buy enough watt-hours for that small set of devices to run for the outage window you actually care about.

References

1. The 3 Best Uninterruptible Power Supplies (UPS) of 2026 — Wirecutter
2. How to Choose the Right UPS for a Smart Home — HomeTechHacker
3. How Many Watts does a Wifi Router Use? — EnergySage
4. Hurricanes in 2024 led to the most hours without power in the United States in 10 years — U.S. Energy Information Administration
5. U.S. electricity customers averaged five and one-half hours of power interruptions in 2022 — U.S. Energy Information Administration