AC Energy Consumption Calculator
How much electricity does an air conditioner use? Estimate its units per day and month, its running cost, and the solar needed to cover it, using your AC's rating, your room, and your local climate. It works for split, window, and inverter units.
Your AC's running cost
In its busiest month near Los Angeles, this AC uses about 66 kWh and costs about $12.
| Jan | 0 kWh |
|---|---|
| Feb | 0 kWh |
| Mar | 0 kWh |
| Apr | 0 kWh |
| May | 0 kWh |
| Jun | 43 kWh |
| Jul | 66 kWh |
| Aug | 66 kWh |
| Sep | 55 kWh |
| Oct | 39 kWh |
| Nov | 0 kWh |
| Dec | 0 kWh |
Assumptions used
- Efficiency (COP)
- 4.7
- Months needing cooling
- 5
- Yearly use
- 270 kWh
- Hottest period outside
- 29°C
Where the heat comes from
Thicker arrows carry more heat. Try a higher thermostat setting or better shading.
What if?
Save this result, change any setting, and compare.
How this is calculated
Heat entering the room
We estimate heat from outside air, sun, and people, then add 25% for humidity and leaking air. Better insulation and a higher thermostat setting both reduce it. Outside temperature comes from monthly climate data for your location.
Heat (W) = (leakage × floor area × (outside − setpoint) + sun + 100 W per person) × 1.25
Electricity used
An AC moves more heat than the electricity it uses. We convert its rating to that ratio, called the COP. SEER and EER are divided by 3.412, and ISEER is used as it is. Inverter units gain efficiency when running slowly.
Power (W) = heat removed ÷ COP
Solar needed
We divide the yearly use by what 1 kW of solar produces at your location. The sun often shines when cooling is needed, but it does not cover night-time use without a battery or net metering.
Worked example: a 3.5 kW AC in Los Angeles
A 20 m² room with average insulation, cooled to 24°C for 8 hours a day, uses about 66 kWh in its hottest month.
Across the 5 months that need cooling, that adds up to about 270 kWh a year, or about 0.1 kW of solar.
How accurate is this?
This is a simple heat balance, not a full building model. Use it to compare options and understand costs. Real use depends on humidity, window size, air leaks, and how you run the unit. Your own electricity bill is the best check.
Common mistakes
- Multiplying the rated power by hours, which ignores the compressor cycling
- Mixing up cooling capacity with electrical power
- Comparing SEER, EER, and ISEER as if they were the same scale
- Forgetting that each degree cooler uses more energy
Limits of this tool
- Humidity is a simple 25% allowance, so very humid places may use more
- Monthly average temperatures smooth out heatwaves
- Heat from cooking and appliances is not included
What to do next
- Check your total bill with the electricity bill calculator
- Size your system with the solar system size calculator
Frequently asked questions
How many units does a 1.5 ton AC use per hour?
A 1.5 ton AC has about 5.3 kW of cooling. With a COP of 4, it uses about 1.3 units an hour at full power, and less when the room reaches its setting.
Does an inverter AC save electricity?
Usually, at part load. It slows down instead of switching off and on. The saving depends on the unit, the room, and how you use it.
How much solar do I need to run an AC?
Divide its yearly electricity use by your local yearly output per kW. This calculator does that for your location.
What is the difference between SEER and EER?
EER measures efficiency at one test condition. SEER covers a typical cooling season. Both are in BTU per watt-hour in the United States.