In this guide
- The restart sequence: what comes back, in what order
- Power-on states: what each device should come back as
- Inverters, DG changeover and the double blip
- Missed schedules and catch-up logic
- What to put on inverter or UPS backup
- A worked example: a 9:40 pm outage in a 3BHK
- Mistakes that make power cuts worse
- How Pert delivers it (designed, not DIY)
- FAQs
This article is part of our wider coverage of home automation in Hyderabad. For what keeps working while the power or internet is out, see do smart homes work during power cuts and internet outages. For the wiring side, including neutrals, earthing and surge protection, see electrical safety and power protection for a smart home. This guide is about the recovery itself.
The restart sequence: what comes back, in what order
In a Pert home, keypads, lighting controllers, curtain motors and sensors talk over Zigbee through the Pert gateway. When power returns, they do not all wake up at the same speed. A typical order looks like this:
| Stage | What is happening | What you notice |
|---|---|---|
| First second | Lighting drivers and controllers get power and apply their power-on state | Some lights come on, some stay off, depending on how each was configured |
| First few seconds | Keypads and other mains-powered Zigbee devices restart | Keypad backlights return; a press may not do anything yet |
| Up to a few minutes | The gateway boots and the mesh re-forms as routers find each other again | Keypads start working; the first commands can feel slower than usual |
| A few minutes | Battery sensors that lost their parent router re-attach to the mesh | Motion and door sensors resume reporting |
| Often the slowest | The fibre modem and Wi-Fi router reconnect to the internet provider | The app works away from home again; voice assistants and alerts return |
Two points matter here. First, nothing needs re-pairing. The gateway and every device store their network membership in memory that survives power loss, so the mesh rebuilds itself. Second, local control returns before internet control. Keypads and scenes depend on the gateway, not the internet, so they come back well before the app works from outside the home. How the mesh routes messages, and why mains-powered devices act as its backbone, is explained in how a Zigbee mesh network works. What the gateway itself is responsible for is in what does a smart home gateway do.
Power-on states: what each device should come back as
Every load needs a deliberate answer to one question: when power returns, should it be off, on, or as it was? Zigbee lighting devices that support it can be set to one of these start-up behaviours, and the right choice differs by room. Leaving everything at the factory default is how bedrooms end up lit at 2 am, because many lights default to "on" so they still work from a plain wall switch.
| Load | Recommended power-on state | Why |
|---|---|---|
| Bedroom lights | Off, or previous state | A night-time outage must never end with bright light over a sleeping person |
| Living, dining and kitchen main lights | Previous state | If the family was in the room with lights on, they come back as they were |
| Foyer and one corridor light | On, at a low level | A guaranteed path light after an outage, without needing the gateway or the app |
| Decorative, accent and cove lighting | Off | Nobody misses them in the first minute; they return with the next scene |
| Motorised curtains | Stay where they are | A curtain must never move by itself just because power returned, least of all at night |
| AC through an IR blaster | Depends on the AC's own auto-restart setting | The IR blaster cannot see whether the AC is on, so the AC's setting decides |
| Locks, door sensors, cameras | Same as before; alerts resume | Security should come back as it was, with no gap in the arming state |
"Previous state" is not always what it sounds like
A light can only return to the state it remembers from just before the cut. If the outage hit during a fade, or just after someone pressed Good Night, the remembered state may not be the one you expect. That is why bedrooms are usually safer on "off" than on "previous", and why the foyer path light is a fixed "on" rather than "previous".
Curtains need checking, not assuming
Curtain motors store their open and close limits, but whether a motor knows its exact position after a cut, and whether it needs a calibration run to the end of the track, varies by motor. This is checked during commissioning by cutting the power deliberately. How motorised curtain automation works covers limits and positions.
AC is the honest exception
Air conditioners controlled through an IR blaster behave according to their own setting. Many have an auto-restart option that returns them to their last mode when power comes back; some do not. The automation system cannot confirm either way, which is why scenes send a definite state (on at 24°C, or off) rather than a toggle. How AC automation works explains the limits of IR control.
Inverters, DG changeover and the double blip
Most Hyderabad homes do not see a clean cut and a clean return. They see a short gap, a switch to backup, and another gap when mains returns. Each gap is a restart for anything that is not protected.
Home inverters
Common home inverters offer a UPS mode with a very short changeover, often quoted at around 10 milliseconds or so, and a wider "normal" or appliance mode with a longer changeover meant for fans and motors. Most electronics ride through the short changeover, but some LED drivers, routers and controllers may restart in the wider mode. If the automation equipment is on the inverter, the inverter should be set to UPS mode, and this is tested during commissioning by switching the mains off.
DG backup in gated communities
Many apartment communities and villa layouts in Hyderabad have a diesel generator for common areas and part or all of each home. The generator usually takes several seconds, sometimes longer, to start and pick up the load, and the return to grid power causes a second short interruption. To the smart home, a single outage is therefore two restarts a few minutes or hours apart. Power-on states have to be correct for both, and a home that behaves well after one restart but badly after a second, closely spaced one, is not finished.
Voltage dips and brownouts
Storm-season dips can be long enough to restart some devices and not others. That produces the strangest recoveries: half a room resets, the other half carries on. A stable supply to the gateway and network equipment, through a small UPS, removes most of this, because the brain of the system never restarts and can put the rest of the house back in order.
Missed schedules and catch-up logic
A schedule is usually an event at a moment: "at 6:30 pm, run Evening". If the gateway was off at 6:30 pm, that event is generally missed and not replayed later. That is often the right behaviour. Nobody wants a 7:00 am Morning scene to open the curtains at 11 am because power came back late. But some functions should catch up, and that needs rules based on state rather than a single moment.
| Function | Missed during an outage | Catch-up rule worth having |
|---|---|---|
| Evening lighting | Home stays dark after power returns | If power returns after sunset and the home is in Home mode, apply a low evening level in living areas |
| Away-mode presence simulation | Lights stop following the pattern | Away mode resumes its pattern from the current time, not from the start |
| Night path lighting | Path lights not armed | Night mode re-arms automatically if power returns between bedtime and morning |
| Morning curtains | Curtains stay closed | No catch-up. Opening curtains late, unannounced, is worse than not opening them |
| Security arming | Must not change | Arming state is kept as it was; an alert reports that power was lost and restored |
Time also matters. A gateway that relies on the internet for its clock may run time-based rules wrongly if the internet is still down when it restarts, so it is worth asking how the system keeps time through an outage. More on time windows and sunset rules is in how to schedule home automation, and on house modes in how home automation modes work.
What to put on inverter or UPS backup
Backup is usually planned in tiers. The first tier costs very little and protects the whole system. The rest depends on the inverter or DG capacity the home has.
- Tier 1: the brain and the network. Gateway, Wi-Fi router and fibre modem on a small dedicated UPS. Together they draw a small amount of power, so a compact UPS can usually keep them running for hours. This one step means keypads, scenes, app access and alerts never restart during short cuts.
- Tier 2: one light per room and every keypad. At least one lighting circuit per room, plus the foyer and corridor path lights, on the inverter. Wall keypads are usually powered from the switch box they sit in, so the circuits feeding them should be backed up too, or the keypad goes dark exactly when someone reaches for it.
- Tier 3: curtains and security. Motorised curtains draw power only while moving, so they sit comfortably on most inverters. Mains-powered cameras, video door phones and any mains-powered locks should be on backup too. Battery locks and sensors already ride through. See Pert security.
- Tier 4: comfort loads on DG only. Air conditioners and large appliances are normally left off the inverter and run only where the building has DG backup for them.
The key design rule: the gateway should never be on a circuit with less backup than the devices it controls. A house where the lights are on the inverter but the gateway is not keeps its lights through an outage but loses every keypad scene.
A worked example: a 9:40 pm outage in a 3BHK
A 3BHK in a Hyderabad gated community with DG backup for lighting and fans. The gateway, router and modem are on a small UPS. Lighting, keypads and curtains are on the DG-backed circuits. The family is in the living room with the Evening scene on; one child is already asleep with the bedroom in Good Night.
| Time | Event | What the home does |
|---|---|---|
| 9:40:00 pm | Grid supply fails | Lights go out. Gateway, router and modem stay up on the UPS. Battery sensors and locks are unaffected |
| 9:40:15 pm | DG takes the load | Living room lights return to their previous state (Evening). Child's bedroom stays off. Foyer path light comes on at low level. Curtains do not move |
| 9:40:20 pm | Keypads restart | Because the gateway never went down, keypads work within seconds and backlights show the correct scene |
| 9:41 pm | Alert | The owner gets a "power interrupted and restored" notification; the AC in the master bedroom, on grid only, is noted as off |
| 10:55 pm | Grid returns; second short interruption as the DG hands back | Same power-on states apply again. The sleeping child's room stays dark. Night mode, already set by Good Night, stays armed |
Change one thing and the evening goes differently: if the gateway were not on the UPS, every keypad would be unresponsive for the first minutes after each interruption, twice in one night. That single small UPS is the cheapest reliability upgrade in the house.
Mistakes that make power cuts worse
- Leaving factory power-on defaults. Lights that default to "on" will light up every room, including bedrooms, after every cut.
- Gateway on the grid, lights on the inverter. The lights survive but the control does not.
- Inverter in its wide changeover mode. Electronics restart on every changeover. Use UPS mode for circuits with automation.
- Testing with only one restart. DG homes see two interruptions per outage. Test both.
- Curtains that open after power returns. No curtain should ever move just because power came back.
- Morning schedules that catch up late. Some events should simply be skipped if missed.
- No alert for power loss. Especially when the family is away, a short "power lost and restored" message tells you whether the fridge, cameras and AC need checking. Alert design is covered in how to design smart home notifications.
How Pert delivers it — a designed solution, not a DIY kit
Pert designs and installs the whole system: keypads, tunable and dimmable lighting, motorised curtains and security devices, working together over Zigbee through the Pert gateway. Power recovery is part of that design, not an afterthought. During design, we agree with you which circuits are on inverter or DG backup, where the gateway and network equipment get their protected supply, and the power-on state of every lighting circuit room by room. During commissioning we cut the mains deliberately, including a second interruption to simulate a DG handover, and check that every room comes back the way it was agreed. The result is recorded in your handover document. If you add an inverter or change your backup later, we review the power-on settings with you.
Planning home automation for a Hyderabad flat or villa? We will design the keypads, scenes, lighting, curtains and security as one system, including what happens in every room after a power cut, inverter changeover or DG handover. Request a consultation →
Comparing installers? Ask each one what your lights will do when power returns at 2 am, whether the gateway should be on backup, and whether they test a power cut during commissioning. Those questions sit alongside the wider checklist in best home automation companies in Hyderabad.
Frequently asked questions
Why do smart lights turn on by themselves after a power cut?
Many smart lights and drivers are set by default to switch on when power returns, so that they still behave like normal lights if someone uses the wall switch. In a designed system, the power-on state of each load is chosen deliberately: on Zigbee devices that support it, a light can be set to come back off, on, or at its previous state. Bedrooms and anything that could wake people at night are usually set to stay off or return to their previous state, not to come on at full brightness.
Do I need to re-pair my smart home devices after a power cut?
No. In a Zigbee system the gateway and every paired device store their network membership in memory that survives a power loss. When power returns, mains-powered devices restart and rejoin the same network automatically, and battery sensors, which never lost power, reconnect as the devices around them come back. The mesh may take a few minutes to settle, so the first commands after a long outage can feel slower, but nothing needs to be paired again.
Which parts of a smart home should be on an inverter or UPS?
At minimum, the gateway, the Wi-Fi router and the fibre modem, so control, app access and alerts survive the outage. These draw little power, so a small dedicated UPS can usually keep them running for hours. After that, put at least one lighting circuit per room, the keypads, and the motorised curtains on the inverter, along with door locks and cameras if they are mains powered. Air conditioners are normally left off the inverter and only run on DG backup where the building has it.
What happens to an automation scheduled during a power cut?
If the gateway was off when a schedule was due, that schedule usually does not run later on its own, so a 6:30 pm Evening scene missed during an outage simply does not happen. A well-designed system handles this with rules based on state rather than a single moment, for example, if power returns after sunset and the home is in Home mode, apply the evening lighting. Whether and how this catch-up logic is set up is agreed during design.