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Smart guide

Stoves, ovens and dishwashers

Cooking uses about 6 per cent of an average household's energy bill, and a lot of that energy is wasted.

Using smart appliances smartly

Today you can buy a range of major kitchen appliances with a wide variety of different features. Choosing the right ones and using them appropriately can save on energy costs and also be good for the environment.

Stoves

The 'exposed coil' element you find on most stoves isn't particularly efficient. It heats the pot and the air around it, as well as the food. The solid disk elements found on some stoves are even less efficient.

Induction elements are the most efficient type of stove element on the market, using about half the energy of an exposed coil element. They heat the pot or pan using a strong magnetic field, while the element itself stays fairly cool. You will need the right types of pots and pans to work with induction elements, but they should be available in your local stores.

Ceramic glass stoves and halogen elements are also more efficient than exposed coil elements. The elements are under glass, which makes them easier to clean.

Both halogen elements and gas burners provide instant heat, so they don’t waste a lot of energy as they warm up.

Ovens

Modern conventional ovens are well insulated, but only about 10–15 per cent of the energy they use actually cooks the food. The rest is just heating the air.

Gas ovens are even less efficient than electric ones because they need higher air flows to provide oxygen for combustion and often have a glow-bar that continuously runs in order to reignite the gas flame should it blow out.

Convection or fan ovens use about 20–30 per cent less energy than conventional ovens, and you can cook more items at the same time because heat is more uniformly distributed.

The good news is that self-cleaning ovens are more efficient than standard ones because they have more insulation. So what’s good for convenience is also good for your wallet and the environment.

Microwave ovens are much more efficient than other types of electric oven. About 50 per cent of the energy they use actually cooks the food. Unlike conventional ovens, microwaves only heat the food, not the surrounding air.

Saving energy when using cooking appliances

To save energy when you're cooking:

  • use a microwave when feasible (they are more energy efficient than ovens or stoves)
  • cook bigger meals so you have enough for another meal (you can always freeze the leftovers)
  • use the right appliance for the job (for example, a kettle rather than a pot for boiling water and a toaster rather than the oven grill for making toast
  • use pots and pans that are flat-bottomed and retain heat well
  • use the right-sized element for your pot or pan and cook with the lid on (this will reduce condensation as well as save energy)
  • make sure appliances are operating efficiently (for example, make sure heat isn't leaking from your oven and keep reflector pans under elements clean and shiny)
  • keep oven doors closed as much as possible
  • allow frozen food to defrost before cooking
  • use a pressure cooker.

Dishwashers

Dishwashers use water, energy and detergent, all of which cost money and have effects on the environment. If you're choosing a dishwasher, look for a model that:

  • is the right size for your needs – if you choose a machine that's too big, you'll be tempted to run it when it's not full
  • is energy efficient
  • has an eco-cycle
  • heats its own water
  • is water efficient – an inefficient dishwasher will use about 23 litres of water per load, whereas the most efficient models now use 6–7 litres, or less on eco-settings.
  • is ENERGY STAR qualified – super energy efficient.

Choosing energy efficient appliances has more information.

You can search the Australian Government’s Water Rating website for water-efficient dishwashers

Is it better to wash dishes by hand?

Not necessarily. Washing by hand frequently involves rinsing under running water first and this wastes more water than you'd think.

According to Consumer New Zealand testing, hand washing the amount of dishes that fit into a dishwasher will use 40 litres of water and cost about 13 cents. If you rinse the dishes with hot water (before or after), the cost increases. A dishwasher on economy cycle will pre-wash, wash and rinse for 13 cents.

If your dishwasher is the right size for your household and you use its eco-setting, you're probably already saving water and energy.

To save energy and water when you use a dishwasher:

  • avoid rinsing dishes under the hot tap – instead, scrape plates well before loading them into the dishwasher
  • clean the filter regularly
  • run the dishwasher only when fully loaded
  • select the cycle with the lowest temperature and the minimum time to get the job done – use the eco cycle if possible.

Tips on detergent

Many dishwashing detergents contain alkalis that can cause severe burns to the mouth, throat and airways if they're swallowed.

These detergents can also be harmful to the environment – for example, some contain phosphates which can get into waterways and cause toxic algal blooms.

To protect yourself and the environment, read the labels and choose detergents that:

  • are enzyme-based
  • don't use metasilicate or silicates as a major ingredient (used to control water hardness, but if swallowed could cause severe burns to the throat, nose or windpipe)
  • don't contain sodium perborate (an active form of oxygen used to whiten, brighten, clean, and deodorise, but is harmful if swallowed, toxic by inhalation, irritating to the respiratory system, and may cause serious damage to the eyes)
  • don't contain phosphates (used to soften the water but can cause excess algae growth in rivers and streams)
  • are licensed to use the Environmental Choice eco-label (look for the government-endorsed black tick and licence number, or look on the Environmental Choice New Zealand website for more information).

If the label doesn't state the ingredients, avoid the product.

Consumer New Zealand tested a number of detergents in 2010 and found that some products marketed as eco-friendly were misleading and potentially dangerous.

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Other resources

  • Appliances

    You’ll find tips for choosing efficient appliances on EECA’s Energywise website.

  • Consumer NZ

    Subscribe to Consumer NZ for more information on products, including independent tests and reviews.

Note that this document is published by the Ministry of Business, Innovation and Employment Chief Executive as Guidance under Section 175 of the Building Act 2004. This is a guide only and, if used, does not relieve any person of the obligation to consider any matter to which the information relates according to the circumstances of the particular case.