SnapEnergyLab

Appliance running costs

Cost to run an air conditioner (window, portable and room units)

An air conditioner does not draw its rated power continuously in most homes. This page applies that behaviour — cycling operation at 60% duty — and shows every step of the arithmetic.

How much does a 1,200 W air conditioner cost to run?

A 1,200 W air conditioner switched on 8 hours per day at 60% duty cycle uses 5.79 kWh of electricity per day. At $0.180/kWh that is $1.04 per day, about $31.73 per average month and $380.79 per year — 2,115 kWh over the year. Those figures assume a typical wattage and a typical usage pattern; change any input below to match your own appliance and tariff.

Your inputs

Typical example — replace this 1,200 W default with your appliance’s actual rating for a better estimate.

This appliance cycles — typical range around 60%.

Applies only to the 16 h a day the appliance is switched off, not to the idle part of the duty cycle.

Use the total variable rate from your bill, including delivery charges per kWh.

Scenario: hours per day

$31.73

per month (30.44-day average month)

5.79 kWh per day at 1,200 W

Estimate using typical assumptions
Per day
$1.04
kWh / month
176
kWh / year
2,115
Per year
$380.79

Average power across 24 hours

241 W

Daily energy spread evenly over 24 hours. Includes standby draw during switched-off hours when entered.

Cost per running hour

$0.130

While the appliance is actually drawing power.

Effective duty cycle

60%

Share of switched-on time at rated power.

Method

  1. 1,200 W = 1.2 kW
  2. 1.2 kW × 8 h/day × 60% duty = 5.76 kWh/day active
  3. 2 W standby × 16 h/day off = 0.032 kWh/day standby
  4. 5.76 + 0.032 = 5.792 kWh/day total
  5. 5.792 kWh × 0.18 USD/kWh = 1.043 USD/day
  6. 1.043 × 30.436875 days = 31.732 USD/month
  7. 5.792 kWh × 365.2425 days = 2115.485 kWh/year
  8. 2115.485 kWh × 0.18 USD/kWh = 380.787 USD/year

Monthly figures use a 30.44-day average month, 365.24-day average year.

Assumptions

  • Electricity rate of 0.18 USD/kWh (editable).
  • Calculations use a year of 365.2425 days and an average month of 365.2425 ÷ 12 = 30.436875 days, so twelve average months equal one year exactly. Displayed values are rounded to 365.24 and 30.44 days, and the rounded figures do not multiply out exactly.
  • Duty cycle of 60% — the appliance draws rated power for that share of the time it is switched on.
  • 2 W standby draw for the 16 hours a day the appliance is switched off. Standby applies only outside the switched-on hours, not to the idle part of the duty cycle, and is included in every kWh and cost figure below.
  • Rated power is treated as real power in watts, not volt-amps.

What can change the result?

  • Compressor duty cycle, which tracks outdoor temperature
  • Whether the unit is single-speed or inverter-driven
  • Thermostat setpoint and room insulation
  • Unit efficiency (EER/SEER) — the same cooling can need very different input power

$31.73/mo · 176 kWh/mo

How a air conditioner actually draws power

An air conditioner is a heat pump running in reverse, and its input power is not fixed. A single-speed unit cycles the compressor on and off — the fan keeps running, the compressor does not. An inverter unit instead modulates, drawing high power to pull the room down and then settling at a much lower steady draw. Input power also rises as outdoor temperature rises, because the machine has to reject heat against a hotter outside.

The duty cycle below matters more than the wattage. On a mild day a unit may run 30% of the time; during a heatwave it can approach 100%. Cooling capacity in BTU is not electrical power — divide BTU/h by the unit's EER to get watts drawn.

Window, portable and central AC: how many watts?

This calculator models one room air conditioner — a window unit, a portable unit or a single small split head. Input power depends on cooling capacity and efficiency: watts ≈ BTU/h ÷ efficiency rating (CEER for window units, SACC-based ratings for portables). Portable units are generally less efficient than window units of the same nominal size, so they draw more power for the same cooling. Keep the wattage editable and use your own unit's label where you can.

Cost per hour assumes the compressor runs the full hour. Real use is lower when the compressor cycles; set the duty cycle in the calculator. Central systems also include an indoor blower and are rated seasonally (SEER2), so they are not the same electrical model as a room unit.
TypeTypical wattsCost per hour at full power ($0.180/kWh)Basis
Small window AC (5,000–8,000 BTU/h)about 450–750 W$0.108 at 600 WIllustrative range
Larger window AC (10,000–12,000 BTU/h)about 850–1,200 W$0.180 at 1,000 WIllustrative range
Portable AC (8,000–14,000 BTU/h nominal)about 900–1,500 W$0.216 at 1,200 WIllustrative; usually less efficient than window units
Central AC (2–5 tons)about 2,000–5,000 W$0.630 at 3,500 WDifferent system — use BTU-to-watts with its SEER2/EER2, not this room-unit default

Cost at different usage patterns

All rows use 1,200 W at 60% duty and $0.180/kWh. Only the hours change.

Generated by the same energy engine that powers the calculator above.
Hours per daykWh per dayPer dayPer monthPer year
4 h/day2.92 kWh$0.53$16.00$191.97
6 h/day4.36 kWh$0.78$23.86$286.38
8 h/day5.79 kWh$1.04$31.73$380.79
12 h/day8.66 kWh$1.56$47.47$569.60

Cost across the typical wattage range

Units in this category typically range from 500 W to 3,500 W. All rows use 8 h/day at 60% duty.

Source for the range: Typical input power of window and small split air conditioners (2026-01).
Power ratingkWh per dayPer dayPer monthPer year
500 W2.43 kWh$0.44$13.32$159.89
1,200 W5.79 kWh$1.04$31.73$380.79
3,500 W16.8 kWh$3.03$92.22$1,107

The decision that changes this cost: raise the setpoint a couple of degrees

Compressor duty cycle tracks the gap between indoor setpoint and outdoor temperature. Raising the setpoint from 21°C to 24°C on a warm-but-not-extreme day can cut the compressor's running share from around 60% to around 35%.

Both rows computed by the same engine at $0.180/kWh — only the change described above differs.
ScenariokWh per yearCost per year
Air conditioner as defaulted above2,115$380.79
Raise the setpoint a couple of degrees1,239$223.00 — saves $157.78/yr (877 kWh)

Where a air conditioner sits in the home

Ranked by annual running cost at each appliance's default usage pattern, this air conditioner is number 5 of 16 in the SnapEnergyLab catalogue — $380.79 per year at $0.180/kWh. The appliances either side of it:

Every appliance at its own default wattage, hours and duty cycle, same engine, same rate.
RankAppliancekWh per yearCost per year
#4Dehumidifier2,191$394.46
#5Air conditioner (this page)2,115$380.79
#6Clothes dryer948$170.67

Worth knowing

BTU rating describes cooling output, not electricity input.

Worth knowing

Compressor start draws a brief surge well above running watts, which matters for battery backup and generator sizing.

Your next decision

Your next decision

Other appliance running costs

Electricity cost tools

Defaults on this page come from the published default registry and the formulas are documented in the methodology.