How to Determine Whether you Have Single or Three Phase Power

  • Tuesday, 2nd February, 2021

Single and three phase power is a term that isn’t used in common day to day conversation. Therefore many of us don’t fully understand what it is or how it works.

What is ‘single’ and ‘three’ phase power?

Single or three phase power refers to the power supply coming into your property by way of underground or overhead power from the street. Most houses would generally have single-phase power. Three-phase power is typically used in commercial/industrial situations and large homes with multiple large electric appliances drawing larger currents of electricity. If your property is drawing a lot of power, three-phase power would be installed to avoid power fluctuation.

How can I tell what phase power I have?

  1. Simply locate the switchboard, normally located close to the front of the house or internally in a linen cupboard
  2. In the switchboard there will be multiple circuit breakers. The circuit break named ‘Main Switch’ is how you will identify what phase power is available.
  3. If there is a single circuit breaker (as per image below) this is single (1) phase power. If there are three circuit breakers joined together by one switch (as per image below) this is three (3) phase power.

Single phase circuit breaker                                                    Three phase circuit breaker

Why would our home need three phase power?  

As mentioned above three phase power is only needed in large homes with multiple electrical appliances. You need three phase if you have the following:

  • Large kiln to do ceramics.
  • Large ducted air conditioning, generally above 15 kilowatt cooling capacity.
  • Big electric motors, usually more than 2 kilowatt.
  • Welders or other garage workshop equipment.
  • Large home with many people using electronic devices at peak times.
  • Homes with pools that have large filter pumps that needs to be powered.
  • Homes with multiple fridges and freezers that demand a lot of power.

If you are trying to run these machines or devices off single phase power, the circuit breaker will continue to switch itself off as there is not enough power supply to meet the demand.

How does single and three phase power work?

The power supply comes to the house through wires from the power lines on the street. Single phase has two wires: active and neutral. The neutral wire is connected to earth at the switchboard. Three phase has four wires: three actives (called phases) and one neutral. The neutral wire is earthed at the switchboard.

Is there such thing as 2 phase power?

Yes. Two phase power is generally installed if the single phase power requirements above the maximum demand as calculated by an electrician.  However there is no extra cost to install three phase power therefore is more beneficial to install three phase power as it could potentially be used in the future.


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