How Much Does a 1.5 Ton AC Add to Your Electricity Bill?

How many units does a 1.5 ton AC use per hour?

"1.5 ton" describes cooling output (about 5,100 watts of heat removed), not electricity drawn. What the meter records depends on the AC's efficiency — its ISEER (Indian Seasonal Energy Efficiency Ratio), which is what the BEE star label grades. The seasonal average is simply:

Units per hour ≈ cooling watts ÷ ISEER ÷ 1000

These are seasonal averages: an inverter AC draws more in the first pull-down minutes and much less once the room holds temperature, so a well-insulated room at a moderate setting can beat these numbers, while a west-facing room at 18 °C will exceed them.

The slab trap: AC units are billed at your highest rate

This is the part most cost estimates get wrong. Domestic tariffs in most states are telescopic slabs — the first units are cheap, later units cost progressively more. Your fridge, fans and lights already fill the cheap slabs; the AC's 250–400 units stack on top, landing in the most expensive slabs you touch.

So the honest cost of running an AC is its units × your marginal rate — the rate of the last slab your total consumption reaches — plus the fuel surcharge (FPPA) and electricity duty that most states apply on top. In many states, adding an AC also pushes your total consumption past a slab boundary, silently re-pricing part of your existing usage too (and in states with non-telescopic or subsidy-threshold tariffs, crossing the limit can re-rate the entire bill).

What that costs per month

Marginal domestic rates in India today mostly fall between ₹5 and ₹12 per unit once you are past the lifeline slabs. Using the table above:

Add roughly 5–20% on top for FPPA and electricity duty depending on your state. For your actual slab rates, don't guess — run your summer and winter units through the bill calculator for your DISCOM and subtract: the difference is what the AC really costs you. The appliance cost calculator does the per-appliance version of this math.

Five things that actually cut the AC bill

• Set 24–26 °C, not 18–20 °C. Each degree cooler adds roughly 6% to consumption. 24 °C with a ceiling fan feels like 22 °C and saves 20–30% versus an 18 °C habit — the single biggest free saving.
• Service before summer. Choked filters and dirty condenser coils force longer compressor runs; a ₹500 service routinely saves 10–15%.
• Seal the room. Door gaps, single-pane west windows and uninsulated ceilings are why "the AC runs all night." Curtains and draft strips are cheaper than units.
• Use timer/sleep mode. A room holds its chill; running 5 hours with a sleep curve instead of 8 flat hours cuts a third of the units.
• Do the 5-star math before replacing. Upgrading an old fixed-speed AC (~1.6 units/hr) to a 5-star inverter (~1.0) saves ~145 units/month over an 8 h/day summer — ₹1,000+ per month at typical marginal rates, so heavy users recover the price difference in two or three seasons. Light users (2–3 h/day) may never recover it.

Check what an AC would do to your bill

Take last month's units, add the AC estimate for your star rating and hours from the table above, and run both numbers through the bill calculator for your state. The difference — computed on your DISCOM's real slabs, fixed charges, FPPA and duty — is the true monthly cost of the AC, including any slab boundary you cross on the way.

Frequently asked questions

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