What it costs to run an air conditioner in the United States

Updated August 24, 2026 · Claude AC · 3 sources cited

Cooling is the reason an American electricity bill has a summer shape. Air conditioning accounts for roughly 19 % of residential electricity use nationally — about 254 billion kWh in the most recent Residential Energy Consumption Survey — and some 88 % of US households run it. That national figure hides everything interesting: air conditioning is close to 28 % of total household site energy in Florida and about 2 % in Maine. Your own number comes from three inputs, and only one of them is printed on the box.

The three numbers

• Capacity, in BTU/h or tons — one ton is 12,000 BTU/h.
• Efficiency — SEER2 for central systems and mini-splits, CEER for window units, and an SACC-based rating for portables. Higher means fewer watts per unit of heat removed.
• Your electricity rate. The US residential average sits near 18 cents per kWh in 2026 after several years of mid-to-high single-digit annual increases, and the spread across states is wide enough to overturn every conclusion below.

The arithmetic is one line: watts = BTU/h ÷ efficiency. A 3-ton system at 14.3 SEER2 draws 36,000 ÷ 14.3 ≈ 2,500 W while it runs. Multiply by running hours, divide by 1,000, multiply by your rate.

Cents per running hour, machine by machine

Two rows deserve comment. The mini-split range is not hedging: an inverter compressor spends most of its life at part load, which is where it is most efficient, so its real hourly cost sits well below the full-load figure — the opposite of a single-stage central system, which is either drawing its full 2.5 kW or nothing at all. And the portable is the worst value per unit of comfort in the table, because a single-duct machine exhausts conditioned household air outdoors and pulls hot outside air in through every gap to replace it, so its rated capacity is never what reaches you. That gap is the heart of the window versus portable comparison.

What that becomes on a monthly bill

Running hours are what separate a $80 summer month from a $250 one. The scenarios below all use the same 3-ton single-stage central system at 14.3 SEER2 and $0.18/kWh, varying only the July run hours typical of each climate band:

These are illustrative bands built from the arithmetic above, not survey averages, and a leaky house at the top of one band will comfortably beat a tight house at the bottom of the next. Cooling degree days are the honest local input, and they are published on every state page: the gap between the Gulf Coast and northern New England approaches a factor of ten, which is precisely why a national « average AC bill » figure tells an individual household almost nothing.

When the tariff matters more than the machine

The same 1,050 kWh of July cooling costs about $125 at 12 cents per kWh, about $190 at 18 cents, about $315 at 30 cents, and residential rates above 40 cents exist in Hawaii. A high rate does two things at once: it makes the summer bill hurt, and it shortens the payback on every efficiency measure, from a higher SEER2 tier to duct sealing to shading. That asymmetry is why the same upgrade advice is right in one state and wrong in the next — the efficiency side of the calculation is set out in our SEER2 guide.

The levers, ranked by what they actually return

• Setpoint and setback. Every degree conceded on the thermostat removes running hours, and the effect compounds on the hottest days because the temperature difference the machine fights shrinks. A programmed setback while the house is empty is free money in dry climates; in humid ones keep it modest — 4 to 6 °F — so the system is not fighting a rebuilt moisture load on your return.
• Duct sealing and attic insulation. The largest single lever in the typical American house, and the one nobody advertises because it is not a shiny box. Supply ducts crossing an unconditioned attic lose cooling before it reaches a register; sealing and insulating them usually returns more comfort per dollar than climbing two efficiency tiers.
• Filter and coil hygiene. A choked filter or a matted outdoor coil raises consumption for identical comfort. Ten minutes a month, measurable return, no capital cost.
• Shading the west face. An unshaded west-facing window is the single largest heat gain in most homes on a summer afternoon. Preventing a load always beats paying to remove the heat afterwards.
• Right-sizing at replacement. An oversized system short-cycles, never runs long enough to dehumidify, and costs more to buy — a house that is cold and clammy at the same time. Size to a room-by-room Manual J calculation rather than to square footage.

Three things that do not save money

Closing vents in unused rooms raises duct static pressure, forces more air out through leaks, and can cut total airflow enough to freeze the evaporator coil. Leaving the fan on ON rather than AUTO adds a continuous 300–500 W of blower draw and re-evaporates condensed moisture off the coil back into the house between cycles, which is why houses feel muggier on that setting. And setting the thermostat far below the target to cool faster achieves nothing at all: a single-stage system has exactly one speed, so a 62 °F setpoint changes only how long past comfort it keeps running.

Does an efficiency upgrade pay for itself?

Sometimes, and the honest test is arithmetic rather than enthusiasm. Take the hot-humid row above: moving from 14.3 to 18 SEER2 removes roughly 20 % of cooling kWh, which is about $40 in that peak month and perhaps $150–$200 across a season. Against a typical premium of $1,500–$3,000 for the higher tier, payback lands somewhere in the eight-to-fifteen-year range in long-season states, and effectively never in mild ones. The comfort case for a two-stage or variable-speed system — longer, gentler cycles and far better humidity control — is frequently a better reason to spend the money than the kilowatt-hour line. One change matters for 2026 budgets: the federal 25C credit that used to offset part of this cost expired for property placed in service after 31 December 2025, so buyers now depend on state and utility programmes, which is the landscape mapped in our tax credits and rebates guide.

Frequently asked questions

How much does it cost to run an air conditioner for 24 hours?

For a 3-ton central system at 14.3 SEER2 and $0.18/kWh, the ceiling is about $10.80 if it literally ran every minute. Real systems cycle: on a hot day expect 12 to 16 running hours, so $5 to $8. A window unit in a bedroom, run overnight, costs well under a dollar.

Is it cheaper to leave the AC on all day or switch it off?

For a well-insulated house with an inverter or two-stage system, holding a moderate setpoint through the day usually beats a hard evening pull-down, because the equipment stays at its efficient part-load point. For a leaky house empty all day in a dry climate, the setback wins. The rule of thumb: the more shading, insulation and thermal mass you have, the more « leave it running gently » pays.

Why did my bill jump when the weather barely changed?

Because cooling demand is not linear in outdoor temperature. Consumption tracks the difference between outdoor and indoor temperature, and once the outdoor peak passes your design condition the system stops cycling and runs flat out. A five-degree hotter week can easily add a third to the cooling line, and utilities with tiered or time-of-use rates then push part of that usage into a more expensive block.

Does a smart thermostat actually cut the bill?

It cuts it exactly as much as the setbacks you allow it to make. Its real value is in doing consistently what most households intend and forget: scheduling, geofenced setbacks, and reporting on how many hours the system actually ran. That last figure is the most useful diagnostic a homeowner can have — a system running far longer than the bands in the table above is either undersized or losing its output to the ducts.

How do I work out my own number in one line?

Take the capacity in BTU/h, divide by the SEER2 or CEER rating to get watts, divide by 1,000, multiply by realistic running hours, and multiply by your rate per kWh. A 36,000 BTU system at 16 SEER2 running 300 hours in a month at $0.18: 36,000 ÷ 16 ÷ 1,000 × 300 × 0.18 ≈ $121. Substitute your own tariff from the bill rather than a national average — that is the number that decides everything.

Read next

• Swamp cooler or AC: the dew point decides, not the thermometer
• Recharging an air conditioner: what refrigerant costs, and why topping off is not a repair
• The AC capacitor: the cheap part behind most summer breakdowns
• Reading the nameplate: your air conditioner’s size, age, refrigerant and circuit
• AC maintenance: the yearly rhythm that keeps a system honest

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