Load Shedding in Pakistan: How to Keep Power On (Changeover vs ATS vs UPS)
To keep power on during load shedding you switch your load from the grid to a backup source — generator, inverter/UPS or solar. The device that does the switching is what matters: a manual changeover switch is cheapest but needs you present; an automatic changeover or ATS switches within seconds on its own; a UPS/inverter gives an instant no-break supply for electronics. Whichever you choose, it must make it physically impossible for the grid and your backup to connect at the same time.
Load shedding is a daily reality across Pakistan, and the question is rarely "which generator" — it is "how do I switch to it safely and, ideally, automatically." Here are your options, how to size them, and the one mistake that can kill someone.
The one rule: two sources must never connect
Before any product choice, understand the rule every switching device exists to enforce: your backup source and the grid must never be live on the same wires at the same time.
If a generator feeds back into the grid during a shutdown, it energises the "dead" line workers believe is safe — a lethal back-feed. In the other direction, when the grid returns while your generator is still connected, two unsynchronised sources collide and destroy the generator, the transfer gear, or both.
A proper changeover switch or ATS is mechanically and electrically interlocked so only one source can ever be connected. This is the entire reason the device exists. Never bodge a transfer with two ordinary breakers you flip by hand — a moment's inattention back-feeds the line.
Your three switching options
1. Manual changeover switch
A single interlocked switch with three positions — Grid / Off / Generator. When the power goes, you start the generator and turn the switch to Generator; when the grid returns, you switch back and shut the generator down. The interlock guarantees you can never select both.
It is the cheapest, simplest and most robust option, and for a home with a manual generator it is often all you need. The trade-off is obvious: someone has to be there to operate it. A manual changeover such as the CNC YCBZ-63 covers typical single- and three-phase household and small-shop loads.
2. Automatic changeover / ATS
An Automatic Transfer Switch (ATS) does the same job without you. It senses the grid, and when it fails it transfers the load to the backup — and where wired to do so, signals an auto-start generator to run. When the grid returns, it transfers back and stops the generator, all within seconds.
This is what you want for a shop, office, clinic or any load that cannot wait for someone to flip a switch — or for an auto-start generator or a solar/inverter system that should take over unattended. It carries the same hard interlock as the manual version, so both sources can never connect.
3. UPS / inverter (no-break supply)
A changeover or ATS has a short dead time during transfer — fine for lights, fans and motors, but enough to reboot a computer or drop a router. A UPS or battery inverter bridges that gap with an instant, no-break supply, then rides through the outage on batteries. It is the right tool for electronics and critical loads, and is commonly paired behind a changeover or ATS rather than instead of one.
| Option | Transfer time | Needs you present? | Best for |
|---|---|---|---|
| Manual changeover | As fast as you move | Yes | Homes, small shops, manual generators |
| Automatic changeover / ATS | Seconds, unattended | No | Shops, offices, auto-start gensets, solar |
| UPS / inverter | Instant (no break) | No | Computers, routers, critical electronics |
Sizing the switch to your load
A changeover or ATS is rated in amps and must carry the full current of everything downstream of it — sized to your main incomer, not to the generator. Add up your connected load, or simply match the rating of your main breaker.
| Typical setup | Common switch rating |
|---|---|
| Small home (lights, fans, 1 AC) | Single-phase, up to ~40–63 A |
| Larger home / small shop (2–3 ACs, equipment) | Single- or three-phase, 63–100 A |
| Three-phase premises / larger genset | Three-phase, 100 A and up, to the incomer |
When in doubt, size to your main breaker and leave headroom. An oversized changeover costs a little more; an undersized one overheats.
The overlooked risk: when the grid comes back
Load shedding does not only cut power — it returns it, often unstable. The moment supply is restored, voltage can swing high or low, and on three-phase systems a phase can be missing or out of sequence. That surge back onto your equipment does real damage, especially to motors, compressors and ACs that were running on backup a second earlier.
Two low-cost devices guard against it:
- A voltage protector disconnects the load if the returning voltage is too high or too low, and reconnects after a delay once it stabilises — protecting fridges, ACs and pumps from the swing.
- On three-phase supplies, a phase-sequence relay blocks the load if a phase is missing or the phases return in the wrong order — which would otherwise run a three-phase motor backwards or on two phases.
If you are choosing between a voltage protector and a stabiliser for the grid-return problem, the difference is covered in Voltage Protector vs Stabiliser.
Putting it together: three common setups
Home with a manual generator. Manual changeover switch (Grid/Off/Generator) sized to the main breaker, plus a voltage protector on the incomer for grid-return protection. Simple, cheap, reliable.
Shop or office that cannot wait. Automatic changeover / ATS so the load transfers within seconds unattended, plus a UPS on the till, computers and router for a true no-break supply, plus a voltage protector (and phase-sequence relay if three-phase).
Solar / inverter household. The inverter handles the instant transfer for daily use; a changeover or ATS provides a clean, interlocked way to bring in a generator or the grid as the backup-to-the-backup, again with voltage protection on grid return.
Frequently asked questions
What is the difference between a changeover switch and an ATS?
A manual changeover switch you operate by hand; an ATS (automatic transfer switch) senses the outage and transfers the load automatically within seconds. Both are interlocked so the grid and backup can never connect together — the difference is only whether a person is needed.
Do I really need a changeover switch, or can I just use two breakers?
You need a proper interlocked changeover. Two independent breakers rely on you never having both on at once — and the day someone forgets, the generator back-feeds the grid, which is lethal to line workers and destructive to the generator when supply returns.
What size changeover switch do I need for my home?
Match it to your main incoming breaker. A typical single-phase home uses a 40–63 A changeover; a larger home or small shop, 63–100 A. Size to the load downstream, not to the generator.
Can an ATS start my generator automatically?
Yes, if the generator has an auto-start facility and the ATS is wired to signal it. The ATS detects the outage, starts the generator, transfers the load, and reverses the whole sequence when the grid returns.
Will a changeover switch protect my appliances from voltage fluctuation?
No — a changeover only selects the source. For the voltage swing when the grid returns you need a separate voltage protector, and on three-phase supplies a phase-sequence relay.
Do I need a UPS if I already have a generator and changeover?
For lights, fans and ACs, no. For computers, routers and anything that reboots on a momentary break, yes — the changeover has a brief dead time during transfer that a UPS bridges instantly.
What happens if the grid returns while my generator is running?
With a proper changeover or ATS, nothing bad — the interlock keeps the grid disconnected until you (or the ATS) transfer back. Without one, the two sources collide and typically destroy the generator or transfer gear.
Can I use one changeover for both a generator and solar?
A standard changeover selects between two sources. For three sources (grid, generator, solar/inverter) you either use a multi-position switch or stage the switching — commonly the inverter handles daily backup and a changeover brings in the generator or grid. Size and wire it to your specific setup.
Pick the switching by how quickly you need the transfer and whether anyone is there to do it — then protect what comes back with a voltage protector. The interlock is not optional; it is the whole point.
Related guides
CNC Electric supplies interlocked changeover switches, automatic transfer switches and voltage protectors across Pakistan, with free delivery and cash on delivery. Not sure what your setup needs? WhatsApp +92 326 1111 376 with your load and generator size and we will size it for you.