What is a kilowatt hour?

When contemplating your energy bill, it's easy to zero in on the total balance and ignore the rest. But by looking at how many kilowatt hours (kWh) of energy you've used, you're better equipped to lower the cost of your bill and understand:

• How your retailer has calculated the bill.
• Why certain appliances consume more energy than others.
• Whether you need to work on lowering your energy consumption.

What is a kWh and why is it important?

kWh stands for "kilowatt hour", a measure of energy consumption.

Kilowatt (kW) is a power unit, equal to 1,000 watts (the same unit your light bulbs use). We usually rate appliances in kilowatts: running an appliance rated at 1kW, such as an oven, for a single hour will consume one kilowatt hour (kWh) of energy. An appliance rated at just 10 watts, like a night light, would take 100 hours to consume the same amount of energy.

Energy retailers usually use kWh to measure your house's total power consumption. An average Australian household in South Australia, for example, consumes somewhere around 20kWh per day.

What's the difference between kWh and kW?

While the two look similar, a kW is a measure of power, while a kWh is a measure of energy. They are related, but not the same.

This distinction can be important for determining what power solar array you might need, for example. Let's say you're aiming to generate 20kWh of power each day to cover your energy needs. Sure, you could run an oversized 10kW system for two hours to meet this, but you could just as easily run a 5kW version for four hours if you have the sunlight, which will save you heaps in installation.

You can think of it like taking a road trip. The faster you go, the sooner you arrive – but if you have an extra hour or two, you can get there just the same at a slower speed.

Saving energy using kWh and kW

Understanding kW and kWh can help you save energy in several ways:

• Understanding appliances. Appliances come with a kW energy rating, and only consume energy so long as they're on and connected to an active power supply. Try:
  • Energy-saving light bulbs with lower power ratings.
  • Turning appliances off at the wall instead of leaving them in standby, which can save a lot in passive power use.
  • Updating old, inefficient appliances to newer models to save energy (and money) over time.
  • Defrosting your freezer when the ice gets too thick to make it run more efficiently.

• Adjusting temperatures.
  • Setting your heater to 18-20 degrees in winter and your aircon to 25-27 degrees in summer helps them run well. Each extra degree can raise your energy usage by 10%.
  • Run colder washes in your dishwasher or washing machine to save on hot water costs.

• Insulating. Australian houses are often poorly insulated, leading to lots of wasted energy. Consider:
  • Replacing windows with double glazing. Badly insulated or fitted windows can account for 40% of the heat lost in winter.
  • Filling cavities with decent insulation to stop another huge chunk of heat escaping (or hot air seeping in during summer). Wall, ceiling and floor insulation is often absent or of poor quality.
  • Getting an insulating jacket for your hot water tank, to prevent heat loss.

Find your kWh usage on your bill and get it below households in your area

Your energy bill will list your total energy usage in kWh. The energy retailer should also have a chart comparing your usage to other households in your area of varying sizes, such as a three-person household or a five-person household.

If you're using significantly more energy than other similarly sized households in your area, it's worth investigating why. You can find our tips for saving energy here.

Switch energy providers

Energy retailers charge you for your usage by the kWh. Lowering your power usage is one way of tackling high power bills, but another is shopping around for a better energy plan. You can use the Energy Finder to see what's available to you.

Note: You can use your bill details to get a more accurate estimate.

Image: Getty