UPS / home inverter: units per month in Pakistan
Short answer. A UPS does not generate electricity; it stores it, and it loses roughly 20 to 35 per cent of everything it stores in the round trip. So the units you use during an outage appear on your bill afterwards, plus the losses — which is why installing a UPS reliably raises the bill even though nothing about your usage changed.
Power draw
- Low: 40 W
- Typical: 180 W — the figure used in every calculation below
- High: 600 W
Charging draw depends on how deeply the battery was discharged. Idle standby losses of 15–40 W continue whenever the unit is switched on.
Units and cost by usage pattern
Each row is 180 W × the hours shown ÷ 1,000, over 30 days. The three cost columns exist because the rupee cost of a unit depends entirely on which slab your month lands in — the same consumption costs a light user and a heavy summer household very different amounts. Rates are illustrative and not a substitute for the tariff table printed on your own bill.
| Usage pattern | Units / day | Units / month | At Rs 12.5/unit | At Rs 27.5/unit | At Rs 36/unit |
|---|---|---|---|---|---|
| Light load, two hours of outage a day, recharging | 0.54 | 16.2 | Rs 203 | Rs 446 | Rs 583 |
| Heavier load with several hours of outage | 1.08 | 32.4 | Rs 405 | Rs 891 | Rs 1,166 |
Rate bands: Rs 12.5 — light user, protected (≈150 units/month); Rs 27.5 — average household (≈250 units/month); Rs 36 — heavy summer month (700+ units). This appliance runs all year, so the monthly figure applies in every cycle.
Where the extra units come from
Three places. Charging losses in the battery, which are unavoidable chemistry. Conversion losses in the inverter, turning DC back into AC. And standby losses, which continue all day whenever the unit is switched on and the mains is present.
Together these mean every unit you consume during load shedding costs perhaps 1.3 units on the meter. The convenience is real; so is the premium.
Sizing it honestly
Total the watts of what must genuinely run — lights, fans, the router, perhaps a television. Divide by the inverter's power factor, commonly 0.8, to get the kVA rating. Then check the battery: capacity in amp-hours times battery voltage, times a usable depth of discharge of around 50 per cent for a lead-acid bank, gives the watt-hours actually available.
That last step is where most sizing fails. A 1,000 VA inverter with one small battery cannot run a house for four hours regardless of what the box says, because the limit is stored energy, not inverter capability.
What not to put on it
Anything with a heating element. A geyser, an iron, a kettle or a room heater will flatten a domestic battery bank in minutes and stress the inverter doing it.
An air conditioner needs a substantially larger system than most households have, and starting surge rather than running power is what defeats an undersized one.
How to use less
- Convert lighting to LED before sizing a UPS — it can halve the backup load and therefore the system you need.
- Switch the UPS off entirely during long stretches with no load shedding to avoid standby losses.
- Keep battery terminals clean and the electrolyte topped up on lead-acid banks; a degraded battery wastes more of every charge.
- Do not connect heating loads. They are the fastest way to ruin both the battery and the economics.
Frequently asked questions
Does a UPS increase the electricity bill?
Yes, by roughly 20 to 35 per cent of the energy you draw during outages, plus a small continuous standby loss. It moves consumption in time and charges you a conversion premium for doing so.
Can a home UPS run an air conditioner?
Only a substantially sized system. The starting surge of a fixed-speed compressor is several times its running power, and it is what trips an undersized inverter. Inverter air conditioners are easier on a backup system but still need serious capacity.
Is solar with batteries cheaper than a UPS?
Solar generates rather than merely storing, so it reduces grid units instead of adding to them. It costs far more to install, and net metering rather than batteries is what makes the arithmetic work for most Pakistani households.
Compare with
- LED bulbs — 12 W typical
- Ceiling fan — 65 W typical
- Refrigerator — 160 W typical
- Inverter air conditioner (1.5 ton) — 1100 W typical
Go further
Filed under backup power in the full appliance index. Add your own hours in the consumption calculator, or open your actual bill with the reference number lookup.