Two devices, two problems

Walk into any IT room in Nairobi and you will see at least one of these two boxes sitting between the wall and the equipment. They look similar from the outside. They cost roughly similar money. People use the names interchangeably.

They do completely different things, and confusing them is one of the most expensive mistakes you can make in a Kenyan commercial site.

An AVR (Automatic Voltage Regulator) keeps the voltage steady when the grid is up. It does nothing when the grid is down.

A UPS (Uninterruptible Power Supply) keeps the equipment running when the grid is down. It does very little when the grid is up but unstable.

Most sites that need one actually need both. They protect against different failures.

What an AVR does

A servo-driven AVR like the Vener 7 watches the incoming voltage and corrects it in roughly 10 milliseconds. When Kenya Power swings between 200 V and 260 V across an afternoon, your equipment sees a steady 230 V. When a neighbour fires up a welder and your supply sags to 210 V, your equipment still sees 230 V.

The AVR has no battery. It is purely a regulator. The moment Kenya Power goes off, the AVR is off too.

What it protects you against:

Slow voltage drift across the day
Brownouts and sags from local feeder load
Spikes when the grid recovers from a fault
Phase imbalance on a three-phase supply

What it does not protect you against:

Total power loss
Outages of any duration
Frequency drift (rare in Kenya but real on isolated generators)

What a UPS does

A UPS has a battery and an inverter. When the grid is up, it passes the supply through to your equipment, sometimes with mild regulation. When the grid drops out, the inverter takes over from the battery and your equipment keeps running.

Battery runtime depends on the unit and the load. A typical IT-grade UPS runs a server for five to fifteen minutes, enough to either ride out a short trip or shut things down cleanly.

What it protects you against:

Total power loss
Brief outages (under a minute, ride it through)
Long outages (gives you time to start a generator or shut down)
Brief spikes if it has surge protection built in

What it does not protect you against, on its own:

Sustained voltage swings (the inverter cycles the battery every time it kicks in to correct voltage, which kills the battery in 18 months instead of 5 years)
Frequency drift if the inverter is single-conversion type
Anything beyond the battery runtime

Why most Kenyan sites need both

This is the bit nobody on a hardware shop floor ever explains.

Kenya Power gives you two types of problems on the same supply: swings (voltage all over the place) and outages (no voltage at all). They happen separately. They happen together. Sometimes one causes the other.

If you only have a UPS, every voltage swing wears the battery, because the UPS treats the swing as a fault and switches to inverter mode. Six months in, the battery is half its rated capacity. Eighteen months in, the UPS gives you ninety seconds of runtime instead of the eight minutes it had when new. The first time you actually need it during an outage, it dies.

If you only have an AVR, every Kenya Power outage takes your equipment down hard. Servers crash mid-write, controllers lose state, anything in the middle of a job loses the job.

The right configuration on most commercial sites is:

Kenya Power → AVR → UPS → Your equipment

The AVR sits upstream and feeds the UPS a clean, steady 230 V regardless of what the grid is doing. The UPS sees a textbook supply and only switches to battery during an actual outage. Battery life goes back to rated figures. The AVR handles the day-to-day quality problem. The UPS handles the outage.

When you only need one

There are sites where one of the two is enough on its own.

AVR only, no UPS is fine when:

The equipment can tolerate clean shutdowns (most factory machinery, lighting, motors, compressors)
A generator covers outages (the AVR keeps Kenya Power and the generator both within tolerance for the equipment)
There is no in-progress state to lose (welding sets, fans, water pumps)

UPS only, no AVR is fine when:

The supply is genuinely steady (rare in Kenya, common in well-fed industrial parks with their own substation)
The load is small enough that a higher-end "double-conversion" or "online" UPS can do both jobs (these UPSes regenerate the supply continuously and effectively include AVR function, but cost three to five times more than a basic line-interactive UPS)
You are buying for a single-rack server room and budget allows the online UPS option

For most Kenyan commercial sites: factories, hospitals, hotels, banks, manufacturing, anywhere that mixes IT with motors and lighting on the same panel, the right answer is the standard pairing. AVR upstream of UPS, both correctly sized.

How to size the pair

Size the AVR for your total site load with 25% headroom. The AVR sits at the meter or main distribution board and feeds everything downstream.

Size the UPS for the specific equipment that cannot lose power. Usually this is a small fraction of total site load. A factory might run a 200 kVA AVR for the whole plant and a 5 kVA UPS for the server rack and CNC controllers.

For AVR sizing, see the sizing guide or use the sizing tool. For the UPS itself, the manufacturer of the equipment you are protecting will usually publish a recommended runtime and load class.

So, which do you need?

Walk through the failure modes. If the supply gets dirty for ten minutes right now, what happens? If the answer is "things break," you need an AVR. If the supply goes off completely for ten minutes right now, what happens? If the answer is "I lose work or money," you need a UPS. Most Kenyan sites answer yes to both.

Get the AVR sized first. The AVR keeps the UPS battery alive long enough that the UPS actually works when you need it. Without the AVR upstream, you are buying batteries on a 18-month replacement cycle and getting half the protection you paid for.

Talk to an engineer about sizing the pair, or start with the sizing tool for the AVR side.

AVR vs UPS: Same Enclosure, Completely Different Jobs