About electricity

The electricity we use every day comes to us through power lines. It is generated from power stations around New Zealand and enters our homes, factories, farms, shops and schools.

Making electricity 

Power stations make electricity as we need and use it because it cannot be stored. Electricity can be generated a number of different ways:

• Water
• Wind
• Biomass

Generating electricity in New Zealand 

 Electricity is "made" by generators.

Generators  change one form of natural energy – for example the power of falling water – into another form of energy called electricity; a form of energy we can use.

We generate electricity because although there is a lot of energy in moving water, or in the wind, we cannot use that form of energy to power a light bulb or run a computer hundreds or thousands of kilometres away.

Sources of natural energy

Meridian Energy generates most of its electricity from hydro power and a small portion from wind.

These are both "renewable" or "recurring" forms of energy that cannot be used up. Meridian Energy is also involved in projects producing electricity from rubbish and other organic waste material known as biomass.

Non-renewable sources include natural gas, coal and oil.

• About 70 percent of New Zealand's electricity is generated from hydro power.
• The remainder is generated from geothermal energy (steam from under the ground), gas, oil and coal.

How a generator works

Modern generators have magnets and wires that spin very close to one another. One set of magnets ("rotor") spin inside a set of stationary magnets. The rapidly moving magnets and wires produce "electromotive force", or the process of exciting electrons to jump from atom to atom.

"Electron jumping" is what we call electricity.

Generators use a source of energy – hydro power plants use the motion of water or steam – to move the big fan-like blades in a turbine. The turbine spins the generator.

Getting electricity to your place

There are four steps to getting power to your place. Here’s who is involved along the way.

Generators produce electricity which is then sold into the wholesale electricity market for supply to electricity retailers. Meridian Energy is New Zealand's largest electricity generator and, like most other generators, we’re also an electricity retailer.

• Generators
• Transpower
• Network companies
• Electricity retailers

Generators

Measuring electricity 

Electricity is not stored in measurable units but passes through appliances when we switch them on.

The kilowatt hour

The amount of electricity used is measured in "kilowatt hours".

A kilowatt hour (KWh) is an amount of force (1,000 watts) passing through a gateway (your meter) over an hour. For example:

• A 100-watt light bulb turned on for 10 hours uses one kilowatt hour (100 watts x 10 hours) of electricity.
• Or, a 10-watt nightlight could be on for 100 hours before using a kilowatt hour (10 watts x 100 hours) of electricity.

Voltage is pressure

• The volt is named after the Italian physicist, Alessandro Volta.
• Volts make electricity flow from the power stations, through cables and wires, to your home.
• Volts are like water pushing through a pipe. The bigger the diameter of the pipe, and the more it is pumped, the faster it will move water.
• Volts are shown as a capital V.
• A kilovolt (kV) is one thousand volts.
• Transmission wires operate at high voltages – up to 500,000 volts – to help the electricity travel over long distances.
• Network companies use transformers to change (transform) the electricity to the 220 volts used in your home.

Electricity lost to resistance

Not all the electricity passing through an appliance's circuit – or even through your house wiring – is properly used.

Circuits, and the appliances and devices on them, lose electricity to resistance. In fact, every wire, motor and burner on an electrical circuit resists the flow of electricity to some degree. It therefore loses, or converts, electricity to heat, light, magnetism, pressure, or chemical action.

• In wires, resistance is wasteful and unwanted; it is therefore minimised as much as possible.  
• In other devices on the circuit – such as heaters or lights – resistance is used to do important tasks.

Electricity safety

All of us use electricity every day. But while it's an essential part of our lives, it can also be dangerous or even fatal if used carelessly.

The Energy Safety Service has prepared a handbook as a guide to living safely with electricity. Inside you'll find some valuable information on how to use electricity safely in and around the home.  

• Energy Safety Service
• A Guide to Living Safely with Electricity