Generators and UPS: sizing, cost and what to check

Backup power is a standing household cost in Pakistan rather than an emergency purchase. The two mistakes that cost the most are buying on headline wattage instead of your real load, and ignoring what the thing costs to run once you own it.

Size it to your actual load, not the showroom number

Add up what you genuinely need to run during an outage — fans, lights, a fridge, routers — and remember that motors draw several times their running current at start-up. A fridge or a water pump can trip an undersized unit at the moment it kicks in. Size for that surge rather than the steady figure, then add a modest margin. Anything much beyond that is capacity you pay for twice: once to buy, once in fuel.

Generator or UPS

A UPS carries lights, fans and electronics quietly for a few hours and recharges from the grid, which suits ordinary urban load shedding. A generator runs heavy loads including air conditioning and does not care how long the outage lasts, but it costs far more per hour, needs fuel on hand and needs somewhere ventilated to sit. Many households run a UPS for routine outages and keep a generator for long ones.

What it costs to run

Compare the running cost, not just the purchase price. A generator burns fuel by the hour whether it is half loaded or fully loaded, so an oversized one wastes money continuously. A UPS costs you in grid units to recharge plus battery replacement — and batteries are consumable, so budget for replacing them every few years rather than treating the purchase as one-off.

Buying used

On a generator, ask to see it start cold rather than pre-warmed, listen for knocking under load, check for oil leaks around the head, and ask for running hours and service history. On a UPS, the unit itself rarely fails — the batteries do, and they are most of the value. A cheap used UPS with tired batteries is not a bargain, so price it as the electronics only and assume you are buying batteries.

Carbon monoxide, again

Generators kill people in Pakistan every year through carbon monoxide, usually when run in a garage, a stairwell or under a covered porch to keep them out of the rain. Exhaust must vent to open air, well away from windows and doors. This is not a precaution to take when convenient.

Common questions

What size generator do I need?

Size for the surge, not the steady load. Motors like fridges and water pumps draw several times their running current at start-up, and an undersized unit will trip when they kick in.

UPS or generator for load shedding?

A UPS suits routine urban outages — quiet, cheap per hour, no fuel. A generator handles heavy loads and long outages but costs far more to run. Many households keep both.

What should I check on a used generator?

Start it cold rather than pre-warmed, listen for knocking under load, look for oil leaks at the head, and ask for running hours and service history.

Is a cheap used UPS a good deal?

Only if you price it as electronics alone. Batteries are most of the value and most of the failure risk — assume you are buying replacements.

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