Electrical circuits in your home
Electricity enters your home via a 240v powerline cable into your meter. The meter is usually housed in a meter box which also often contains circuit breakers (or fuses in older houses).
These circuit breakers divert the electricity along small wires running behind your walls and roof, forming separate circuits around your house which deliver electricity to all the switches and powerpoints.
Circuits — sharing the load
The maximum load on each circuit should not exceed 2400 watts. Your house has multiple circuits to help the electrical current stay small, reducing the risk of overloading the circuits. Some appliances, such as a stove, dishwasher, airconditioner/heater or dryer, draw more power and may require their own circuit.
To work out how many watts an appliance is drawing, check the voltage and the amps of the appliance.
Volts x Amps = Watts, so
- 1 Amp at 12 volts = 12 watts
- 1 Amp at 120 volts = 120 watts.
Watts/Volts = Amps, so
- A 1200 watt hairdryer at 120 volts draws 10 amps (1200/120 = 10).
Fuses and circuit breakers automatically block an incoming surge of electrical power over a certain safety limit. When this happens, a fuse will ‘blow’ (melt) and must be thrown out and replaced before you can use that electrical circuit again. A circuit breaker can simply be switched back on.
How many electrical circuits are in my house?
This varies from one house to the next. A typical house in Canberra might have seven circuits (see example diagram below) — two for the lights, two for powerpoints, one for an airconditioner/heater, one for the oven and one for the hotwater system. An apartment would generally have less than this.
Diagram of typical household circuits
The simple way to find out how many circuits you have installed is to count the number of circuit breakers or fuses in your meter box — excluding the main house switch.
Some of the things that can affect how many circuits are installed include:
- the type of appliances you have installed
- the size of your home
- electricity usage outside the premises (such as outdoor lighting or power connected to your garage).
The more energy efficient your appliances, the less electricity they need to draw from your circuits. Learn more about energy ratings and energy efficient appliances.