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How to save electricity in your home

Do you know how much energy your household uses? Do you know what is drawing the most power, pushing up your electricity bill?

If you’ve installed solar power in your home, it helps to be aware of energy guzzlers so you can avoid using them when you need your solar to last during long periods of loadshedding.

The City of Cape Town’s Smart Living Handbook recommends conducting an audit of your electrical appliances: ‘Knowing how much energy your household uses – and what you’re using it for – will help you to prioritise which areas of energy use you could improve in your home.’

Conduct an energy audit

First, here’s a quick rundown on how electricity is measured:

Energy is the capacity to do work and is measured in joules (J). Power is the rate at which energy is used, which is measured in watts (W).

  • One watt is equal to the energy consumed at a rate of one joule per second.
  • A kilowatt equals one thousand watts, and a megawatt equals one million watts.
  • An appliance’s power use is expressed in watts – such as a 5W LED lamp.
  • To understand the total amount of energy used, you need to know how long an appliance is used for – in other words, the amount of energy used in kilowatt-hours (kWh).
  • For example: If a 5W LED lamp is left on for 2 days (48 hours), it will use 5W x 48 hours = 240Wh or 0.24kWh (you divide watts by 1,000 to get kilowatts). A 1kW heater used for 30 minutes will also use 0.5kWh.

Here’s what you have to do:

  • List the electrical appliances you have in your home
  • Note the power in watts each appliance uses – it’s usually given on the appliance itself
  • Note how long (on average) each appliance is in use per day in hours
  • Work out your daily electricity consumption with the following formula: (watts x hours per day) divided by 1,000 = daily consumption
  • To get your monthly average, multiply your daily average by 30

You can put all this information into a table like this one:

Now you can try to identify which areas of your home use the most electricity and see if you can come up with ways to save electricity. Knowledge is power, as they say.

Power-hungry appliances

The handbook notes that appliances such as fridges and geysers switch on intermittently, so it estimates that an electric geyser typically uses 2,600 watts for 4.4 hours a day and that a fridge with a freezer uses 158 watts for 5 hours a day. A solar geyser with electric backup is estimated to use 2,600 watts for only 1.7 hours a day.

Some of the heavier household appliances are:

  • Electric stove: 3,000 watts (typical consumption)
  • Hotplate large: 2,400 watts
  • Kettle: 1,900 watts
  • Toaster: 1,010 watts
  • Dishwasher: 2,500 watts
  • Vacuum cleaner: 1,000 watts
  • Iron: 980 watts
  • Washing machine: 3,000 watts (at 0.75 hours per load)
  • Tumble drier: 3,300 watts (at 0.5 hours per load)

Tips to become more energy efficient

Being conscious of what you use when, and how you use it, can save you 50% or more on your electricity. The City of Cape Town offers the following tips to help cut your electricity costs:

  • Turning down your geyser to 60˚C can save you up to 5% on your electricity bill. A geyser blanket and pipe insulation help prevent heat loss, reducing the amount of electricity needed to keep your water hot.
  • Switching off appliances at the wall and pulling out chargers can save you up to 6% in electricity costs. Standby mode still pulls power.
  • Insulate your ceiling. It slows heat loss, making your home up to 5°C warmer in winter, saving up to 16% of your electricity annually. You can also use a fire instead of an electric heater to save costs.
  • Low-energy bulbs can use 6 times less electricity than incandescent bulbs.
  • Showering instead of bathing can not only save water, but 5 times less electricity too. And if you install an energy- and water-efficient showerhead, you will use up to 40% less hot water.
  • Use an insulation cooker (such as a Wonderbag). This can save up to 60% on energy.
  • Limit the use of your pool pump. A pump running for 10 hours a day uses about 11% of your electricity. In winter, 2 to 3 hours is enough for most pools.
  • Go solar! A solar water heater can save you 25% or more on your electricity bill.

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