Understanding Standby Power Consumption
Modern air conditioning systems can continue to use a small amount of power while in standby. This may be used for electronic controls, communication between the indoor and outdoor units, and components designed to help protect the system.
Why does my air conditioner use power when it is switched off?
Switching your air conditioner off using the remote controller or wall controller normally places the system into standby.
Although the compressor and fans are no longer actively heating or cooling your home, some electrical components may remain energised.
- Electronic control boards
- Communication circuits between the indoor and outdoor units
- Indoor unit electronics
- Protective heaters within the outdoor unit
Understanding electrical measurements
A common source of confusion occurs when electrical current is measured using a clamp meter and the measured amps are then multiplied by the supply voltage.
This calculation represents apparent power. It does not necessarily mean that the air conditioner is actually consuming 312 watts.
Air conditioning equipment contains electronic components and other electrical loads where the relationship between current and actual power consumption can be affected by power factor.
As a result, measuring current alone can make the standby consumption appear considerably higher than the actual electrical power being consumed.
Amps are not the same as watts
| Measurement | What it means |
|---|---|
| Amps (A) | The amount of electrical current flowing through the circuit. |
| Volts (V) | The electrical supply voltage. |
| Apparent power (VA) | Voltage multiplied by current. This is not necessarily the actual wattage being consumed. |
| Watts (W) | The actual electrical power being consumed. |
| Power factor | The relationship between apparent power and actual power consumption. |
How should standby power be measured?
When investigating standby electricity consumption, the most useful measurement is the actual power being consumed in watts.
An appropriate electrical power meter capable of measuring actual watts and power factor provides a more meaningful assessment than relying solely on current measured with a clamp meter.
- Voltage
- Current
- Actual watts
- Power factor
- Whether the indoor and outdoor units are included in the measurement
- Confirmation that the air conditioner is in standby and is not actively heating or cooling
Example of actual standby measurements
During an investigation of multiple air conditioning systems, measurements were taken using an inline electrical power meter.
| Test condition | Measured consumption |
|---|---|
| Outdoor unit only | Approximately 25–30 W |
| Complete system including indoor units | 42.54 W |
| Complete system with outdoor heater disconnected for testing | Approximately 25 W |
| Approximate heater contribution | 17–20 W |
What is the outdoor unit heater?
Some air conditioning systems include a small heater within the outdoor unit.
Its purpose is to assist with equipment protection and reliable system operation under certain operating and environmental conditions.
Depending on the system and conditions, this heater may operate while the air conditioner is in standby and therefore contribute to the normal standby power consumption of the system.
Does standby power mean there is a fault?
Not necessarily.
A small amount of standby power consumption is normal for modern inverter air conditioning systems.
If you believe your air conditioner is consuming an unusually high amount of electricity, the first step is to confirm the actual wattage being consumed, rather than relying only on a current reading from a clamp meter.
If unusually high consumption is confirmed using appropriate electrical measurement equipment, the system can then be investigated further.
Information that can assist with an investigation
If you have concerns about the standby electricity consumption of your air conditioner, having the following information available can help with the assessment:
- Indoor unit model number
- Outdoor unit model number
- Number of air conditioning systems
- Measured voltage
- Measured current
- Actual watts, if available
- Power factor, if available
- Type of electrical meter used
- Confirmation that the system was switched off and not actively heating or cooling when the measurement was taken
Do not remove covers, disconnect components or attempt electrical testing unless you are appropriately licensed and qualified to do so.