What should still work when the internet goes down

Ask someone whose smart home has disappointed them what went wrong, and a surprising share of the answers trace back to one afternoon when the broadband was out and nothing in the house would respond to anything.

This is avoidable. It is a design decision, made at the point of buying, and it is close to impossible to fix afterwards without replacing devices.

The two architectures

Cloud-dependent

You press a button in the app. The command goes from your phone to the manufacturer’s server, which may be in Singapore or Frankfurt or California, and the server sends it back down to the device sitting six feet from you. Your light switches.

Every command makes a round trip across the internet. When the line is down, the trip fails and nothing happens — even though the phone and the light are both working, both powered, and both on the same Wi-Fi.

Many inexpensive Wi-Fi devices work this way, because it is much simpler to build. It also means schedules may live on the server, so “lights on at seven” silently stops during an outage.

Local-first

A hub in your home holds the devices, the schedules and the scenes. Commands go from your phone to the hub over your own network and out to the device. The internet is used for one thing: reaching the hub from outside the house.

During an outage, everything inside the house carries on. The app works on home Wi-Fi, schedules run, motion sensors still turn on lights, scenes still fire. You lose remote access and cloud voice, and that is the whole cost.

How to tell which one you are buying

Manufacturers rarely say this plainly, so use these tests.

• Does it require a hub? Zigbee, Z-Wave and Thread devices need one and are consequently local by design. A standalone Wi-Fi device with no hub is cloud-dependent far more often than not.
• Does setup demand an account before the device will do anything? If you cannot use it at all without registering, the logic probably lives on their server.
• Search the support pages for “offline” or “no internet”. Companies that have done this properly tend to say so; companies that have not tend to be silent.
• Does it offer a local API, Matter, or integration with open home-automation software? That is a strong signal of local capability.
• Test it. The definitive answer: set the device up, then turn off the internet at the router while leaving Wi-Fi running, and try the app. Five minutes and no ambiguity.

What a well-built system does during an outage

Look down the first column. In a properly designed system, an internet outage costs you remote access and voice. Everything you would do while standing in your own house still happens.

Power cuts are a different problem

Worth separating, because people conflate them. In a power cut, mains-powered devices are off and no architecture changes that. What you can do is keep the brain alive: a small UPS running your router, hub and ONT costs little and keeps the network, the sensors, the battery devices and the schedules going through the short cuts that are routine in much of India.

The other half is designing so that a power cut is not a crisis. Battery devices should hold their state. Switch modules should return to a sensible position when power comes back — usually off, so the house does not light up at three in the morning. That last one is a setting, and it is worth checking rather than assuming.

What an outage looks like in a flat that was set up properly

Abstract architecture arguments are less convincing than a walk through an ordinary evening, so here is one. The broadband goes down at seven, as it does, and nobody notices for an hour.

The passage light still comes on at ten per cent when someone walks to the kitchen, because that rule is a motion sensor and a switch module talking to a hub three metres away. The living room lights still come on at their usual time, because the schedule is in the hub. Someone dims them from the app on the sofa, which works, because the phone is on home Wi-Fi and the hub is on the same network.

At nine the bedroom AC comes on at its scheduled time, from an IR controller that was told its schedule once and has kept it ever since. The balcony door is opened and the AC pauses, because a door sensor and a rule handled it locally.

What actually fails: the voice assistant says it is having trouble. Nobody can check the camera from outside the house. A notification that the doorbell rang does not arrive on a phone that is at the office. That is the entire list.

In a cloud-dependent house, the same evening is: nothing responds to the app, no schedule fires, the passage stays dark, and the only thing that works is the wall switch — assuming the installation left the wall switches working, which is a separate argument we make elsewhere and for related reasons.

Which architecture you end up with is largely decided by the radio you choose, because hub-based protocols are local by design and standalone Wi-Fi devices usually are not. That choice is covered in Wi-Fi, Zigbee, Z-Wave or wired.

Questions to ask before you buy

Put these to a supplier, or to a product’s support documentation, and the answers tell you most of what you need to know.

• If my internet is down, can I control this from my phone while standing next to it?
• Where are the schedules stored — on the hub or on your server?
• If your company stopped operating tomorrow, what in my house would stop working?
• Does the device need an account to be set up at all, or only for remote access?
• Is there a local API, Matter support, or an integration with open home-automation software?
• What does the switch do when mains power returns after a cut — on, off, or as it was?

The third question is the one worth watching the face for. Every cloud service in this industry has a finite life, and the honest answer is “the remote access and the app, but the switches, the schedules and the sensors are in your house and would carry on.” If the honest answer is “all of it”, you now know what you are buying.

The practical rules

1. Anything load-bearing must work locally. Lights, locks, gates, anything with a safety aspect.
2. The wall switch is always the fallback. No device should take away the ability to operate a light by hand.
3. Schedules belong in the house. If your hub holds them, they survive anything upstream of your router.
4. Voice is a convenience layer. Never the only route to anything.
5. Put the router and hub on a small UPS. Cheap, and it covers the most common failure in an Indian home.
6. Keep cloud-dependent devices for things that are inherently cloud-dependent — a camera you watch from abroad, a doorbell notification on your phone at work. Those genuinely need the internet. A bedroom light does not.

None of this costs much more than the alternative. It costs attention at the point of choosing, which is the only moment it is cheap.

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