1-Ton vs 1.5-Ton AC in Pakistan: Which Size Is Cheaper to Run
A 1.5-ton unit is not 'more AC' in a small room. It is a larger machine short-cycling. In a large room the 1-ton is the expensive one, because it never stops. Here is that split, costed.
Showrooms in Pakistan default to 1.5-ton. It is the volume seller, it "has extra power", and it is the unit whose pictures are on the glass. Room size is asked late, if at all. That default is why small bedrooms run large machines that never settle, and why large drawing rooms run small machines that never stop.
Both mistakes show up on the bill. This article costs a summer of each, in three rooms, using the same hours and the same illustrative tariff. Inverter versus non-inverter is a different question, already answered on five-year total cost. Here both units are assumed non-inverter so size is the only variable. If you are buying inverter, the direction of the result still holds; the rupees scale down.
The three rooms
| Room | Floor area | What usually fits in a hot, sunny Pakistani room |
|---|---|---|
| Small bedroom | ~120 sq ft (10 × 12) | 1.0 ton is enough if the sun load is ordinary |
| Master / large bedroom | ~180 sq ft (12 × 15) | Borderline — 1.0 ton struggles, 1.5 ton is the common fit |
| Drawing / family room | ~240 sq ft (12 × 20) | 1.5 ton is the minimum that can keep up; 1.0 ton will run flat-out |
Rules of thumb (about 100–120 sq ft per ton in this climate, more if west-facing glass) are not a heat-load calculation. A west wall with no shade can move you up a size. The table is the starting map, not a substitute for a competent installer with a tape.
Summer running cost, 120 days × 8 hours
Draw figures are typical nameplates: 1.0-ton ~1.1 kW while the compressor is on; 1.5-ton ~1.6 kW. Duty cycle is the story:
- Right-sized: compressor on ~70% of the time once the room is cool.
- Undersized: on ~100% — it never catches up, so you get all the kWh and less comfort.
- Oversized: on ~45% — short cycles, still the higher nameplate when it is on, plus worse dehumidification, which is why the room feels clammy.
Energy costed at Rs 35 per unit, an illustrative mid unprotected rate used across this site (not a NEPRA slab; FCA and taxes extra — per-hour AC cost uses the same working rate):
| Room | 1.0-ton summer kWh | 1.0-ton Rs | 1.5-ton summer kWh | 1.5-ton Rs | Cheaper to run |
|---|---|---|---|---|---|
| 120 sq ft (1.0 right-sized, 1.5 oversized) | 1.1 × 0.70 × 960 = 739 | Rs 25,870 | 1.6 × 0.45 × 960 = 691 | Rs 24,190 | Almost a tie on electricity; 1.0 wins on purchase |
| 180 sq ft (1.0 undersized, 1.5 right-sized) | 1.1 × 1.00 × 960 = 1,056 | Rs 36,960 | 1.6 × 0.70 × 960 = 1,075 | Rs 37,630 | Almost a tie on electricity; 1.5 wins on comfort |
| 240 sq ft (1.0 badly undersized, 1.5 right-sized) | 1.1 × 1.00 × 960 = 1,056 | Rs 36,960 and still hot | 1.6 × 0.70 × 960 = 1,075 | Rs 37,630 and actually cool | 1.5 — you are not buying kWh, you are buying a room that works |
The surprise is the middle and the top. In a small room the 1.5-ton does not cost much more to run, because it is off more of the time — but you still paid the extra Rs 15,000–25,000 to buy it, and short-cycling is hard on the compressor. In a large room the 1.0-ton's bill looks similar to the 1.5-ton's while failing to cool, which is the worst possible purchase: you pay, and you still sweat. Size for the room. Do not size for the showroom's default.
Add the purchase premium
If a comparable 1.5-ton costs Rs 20,000 more than the 1.0-ton:
| Room | Five summers of extra running (1.5 minus 1.0) | Plus Rs 20,000 premium | Verdict |
|---|---|---|---|
| 120 sq ft | 5 × (−Rs 1,680) = you save a little on electricity | Still ~Rs 11,600 net extra for the 1.5 | Buy 1.0-ton |
| 180 sq ft | 5 × Rs 670 ≈ Rs 3,350 | ~Rs 23,350 extra for the 1.5 | Buy 1.5-ton anyway — the 1.0 does not cool |
| 240 sq ft | Running cost similar, comfort not | Premium is the price of a usable room | Buy 1.5-ton; consider 2.0 if the sun load is ugly |
Electricity is not the decider in the borderline room. Comfort is. The rupee table is there so you do not buy a 1.5-ton for a 10×12 bedroom "just in case" and then hunt bill cuts that you caused at the till.
Frequently asked questions
Can I put a 1-ton unit in the drawing room "just for sitting"?
You can. It will run continuously and the far sofa will still be warm. That is the 240 sq ft row. Spend the premium or close the doors and cool one end properly.
Does an inverter change the size I need?
It changes how the compressor modulates, not the peak heat it must dump. An undersized inverter still runs near maximum, which is where its efficiency advantage shrinks. Size first, inverter second.
What about 2-ton?
For open-plan rooms well above 240 sq ft, or for a west-facing hall. Do not "future proof" a bedroom with one. The short-cycle problem gets worse as the oversize grows.
Should I believe BTU stickers?
Believe the installer's tape measure more. A tired 1.5-ton that has lost gas behaves like an undersized 1.0. Service is part of sizing; a neglected unit is every size wrong.
Is 26°C still the right setpoint if the unit is undersized?
Yes. Lowering the setpoint on a machine that cannot catch up just keeps it at 100% duty for longer. Fix the size or the insulation; do not fight the thermostat.
Sources and method. Room-size bands are editorial rules of thumb for Pakistani urban rooms with ordinary sun load, not a Manual J heat-load calculation. Power-draw figures are typical nameplates for 1.0 and 1.5-ton non-inverter splits; your rating plate is authoritative. Duty cycles (45% / 70% / 100%) are modelling assumptions to show undersize versus oversize, not measured field data. kWh and rupee figures are original calculations (kW × duty × 960 hours × Rs 35). Rs 35/kWh is an illustrative mid unprotected energy rate, not a published NEPRA slab, and excludes FCA, QTA, fixed charges and taxes. Purchase premiums vary by brand. This is general information, not an installation specification.
