UPS, Generator or Solar? The Cost per Backup Unit, Calculated
A UPS looks cheapest because the battery is bought separately, quietly, every eighteen months. Costed per unit of electricity delivered, the ranking changes completely.
Load shedding forces the same purchase on millions of Pakistani households, and it is almost always made on the wrong basis: the sticker price. A UPS costs Rs 45,000, a generator Rs 120,000, a solar system with storage Rs 600,000, so the UPS wins.
Except a UPS does not include the thing it consumes. Its batteries wear out, get replaced without ceremony every eighteen months or so, and that replacement is never counted as part of what the backup costs. Price each option per unit of electricity actually delivered and the ranking looks very different.
The method
Cost per kWh = (capital ÷ life + consumables + fuel) ÷ kWh delivered per year
Assumptions: a household needing 4 hours of backup a day running fans, lights and a TV — about 0.5 kW, so 2 kWh a day and 730 kWh a year. Grid electricity at Rs 35 a unit for comparison.
Option 1: UPS with lead-acid batteries
| Item | Cost | Basis |
|---|---|---|
| Inverter/UPS unit | Rs 45,000 ÷ 6 yrs = Rs 7,500/yr | 1.2 kVA unit |
| Batteries | Rs 60,000 ÷ 1.5 yrs = Rs 40,000/yr | Two 185Ah tubular, replaced together |
| Charging electricity | Rs 31,930/yr | 730 kWh ÷ 80% round-trip = 913 kWh @ Rs 35 |
| Total | Rs 79,430/yr | Rs 108.81 per kWh |
That battery line is the entire story. Rs 40,000 a year, paid in lumps that feel like maintenance rather than running cost — which is exactly why nobody counts it.
Option 2: Petrol generator
| Item | Cost | Basis |
|---|---|---|
| Generator | Rs 120,000 ÷ 8 yrs = Rs 15,000/yr | 2.5 kVA petrol set |
| Fuel | Rs 273,750/yr | 0.75 l/hr × 1,460 hrs @ Rs 250/l |
| Servicing, oil, plugs | Rs 18,000/yr | Oil change every ~100 hrs |
| Total | Rs 306,750/yr | Rs 420.21 per kWh |
Generators are brutally expensive per unit, for a reason that is structural rather than fixable: a small petrol engine running at a fraction of its rated load burns nearly as much fuel as it would at full load. Running a 2.5 kVA set to power 0.5 kW of fans is paying for capacity you are not using, by the hour.
Option 3: Solar with battery storage
| Item | Cost | Basis |
|---|---|---|
| Panels + inverter | Rs 420,000 ÷ 20 yrs = Rs 21,000/yr | 3 kW system |
| Lithium battery | Rs 280,000 ÷ 8 yrs = Rs 35,000/yr | 5 kWh LiFePO₄, ~4,000 cycles |
| Maintenance | Rs 6,000/yr | Cleaning, occasional service |
| Charging electricity | Rs 0 | Charged from the panels |
| Total | Rs 62,000/yr | Rs 84.93 per kWh |
The ranking
| Option | Upfront | Cost per kWh delivered | vs grid at Rs 35 |
|---|---|---|---|
| Grid electricity | — | Rs 35.00 | baseline |
| Solar + lithium | Rs 700,000 | Rs 84.93 | 2.4× |
| UPS + lead-acid | Rs 105,000 | Rs 108.81 | 3.1× |
| Petrol generator | Rs 120,000 | Rs 420.21 | 12.0× |
The cheapest thing to buy is the second most expensive thing to run, and the most expensive thing to buy is the cheapest to run. That inversion is the whole point — and it is why the sticker price is close to useless as a guide here.
Note also what the solar row is not capturing: those panels generate during the day whether or not the grid has failed, offsetting normal consumption. Counted purely as backup, solar looks expensive. Counted as generation plus backup, its economics are far better — the payback arithmetic for that side is worked through in solar panel cost in Pakistan.
Choosing by usage, not by price
| Your situation | Buy | Why |
|---|---|---|
| 1–3 hrs of outage a day, fans and lights only | UPS | Low capital, and the battery cost stays small at low usage |
| 4–8 hrs a day, sustained | Solar + battery | Lowest cost per unit; capital is repaid by daytime generation |
| Rare, unpredictable, long outages | Generator | Terrible per unit, but you pay only when you run it |
| Need to run an AC | Solar, sized properly, or generator | A domestic UPS cannot carry an AC for long |
| Renting, may move within 2 years | UPS | Solar does not move with you and rarely returns on resale |
The last row deserves emphasis. Solar's economics depend entirely on staying put long enough to collect the return. If there is any real chance of moving inside a few years, the expensive option is the one with the best per-unit cost.
Three ways people overpay
- Buying a generator far larger than needed. Fuel burn tracks engine size more than load, so oversizing costs you every hour it runs.
- Replacing UPS batteries as a matched pair when only one has failed — or worse, mixing an old and a new battery, which kills the new one early.
- Sizing a solar system to peak load rather than to daily energy. Peak sizing sells panels; energy sizing meets your need.
Whatever you buy, the cheapest backup unit remains the one you do not need — every watt removed from your load shrinks every option on this page at once, which is what makes cutting consumption the step that comes before this decision, not after it.
Frequently asked questions
Is a UPS cheaper than a generator in Pakistan?
Per unit of electricity delivered, yes by a wide margin — about Rs 109 per kWh against Rs 420 for a small petrol generator, mainly because a lightly loaded engine burns fuel almost as fast as a heavily loaded one.
How long do UPS batteries last?
Typically 18–24 months of daily cycling for lead-acid tubular batteries in Pakistani conditions. At roughly Rs 60,000 a pair, that replacement is around Rs 40,000 a year and is the largest single cost of running a UPS.
Is solar worth it just for backup?
Costed purely as backup, it is expensive at about Rs 85 per kWh. Its case rests on the daytime generation that offsets your normal bill as well — as backup alone, a UPS is easier to justify for short outages.
What size backup do I need?
Add the watts of what you must run, then multiply by the hours you need them. Fans, lights and a TV come to roughly 0.5 kW; four hours of that is 2 kWh a day, which is the figure to size storage against.
Why is a generator so expensive to run?
Because fuel consumption is driven by engine size more than by load. A 2.5 kVA set powering 0.5 kW still burns close to what it would at a much higher load, so every unit delivered costs several times its grid equivalent.
Sources and method. Every per-kWh figure is computed from the stated assumptions — 2 kWh/day of backup demand, 730 kWh a year, petrol at Rs 250/litre, grid at Rs 35/unit, 80% UPS round-trip efficiency, and the equipment lives and prices shown — as at August 2026. Equipment prices, fuel prices and battery lives vary by brand, city and usage pattern; battery life in particular is heavily affected by depth of discharge and temperature. These are comparative estimates, not quotes for any specific installation.
