Energy

As well as using energy-efficient (i.e. star-rated) appliances, there are a number of other options for increasing efficiency of appliances such as:

• ovens
• cooktops
• microwave ovens
• fridges and freezers
• clothes washers and dryers, and dishwashers

and increasing kitchen energy efficiency in general.

Ovens

Cooking accounts for around 6% of the average New Zealand household energy use, mostly by ovens/cooking ranges. Generally, only a small amount of the energy is actually used for cooking – the rest is in heating the air around the food that is being cooked.

Gas is more efficient than electric for ovens but gas requires a well ventilated kitchen. An air extract system is also recommended.

An electric oven with a fan heats more efficiently than a standard oven. Self-cleaning ovens are more efficient than other types because they have more insulation.

Wood-burning stoves tend to be regarded as a sustainable cooking alternative, but a lot of heat is lost up the flue and much of it also goes into the room. They have less control and produce potentially harmful emissions.

Solar ovens use the sun’s energy as a free heat source to bake, boil or steam food. They use reflectors to concentrate sunlight onto a black cooking pot. Glass or plastic may be used to contain the heat. Food can be baked, boiled or steamed. Solar ovens are the most energy-efficient cooking option, but they are not yet commercially available in New Zealand.

Cooktops

Cooktop (hob) options include gas or electric.

When selecting the energy supply for a cooktop, gas is generally more efficient at transferring heat than electric. If reticulated gas is not available, bottled gas is a viable alternative.

Electric cooktops are available in a range of element types. Options from most to least efficient, options include:

• induction elements, which use a strong magnetic field for heating while the element stays relatively cool – these are currently also the most expensive option
• halogen elements, which have bright halogen lamps under a glass top and give instant heat
• ceramic glass elements, which have electric elements under a glass top
• exposed coil elements, which are the most common but lose heat to the surrounding air
• solid disk elements, which require more energy to heat but do not deliver much more heat to the pan.

Note: Glass tops are easy to clean but can break if a heavy object is dropped on them.

Microwave ovens

About 50% of the energy produced by a microwave oven is used for cooking, making this significantly more efficient than a conventional oven.

Fridges and freezers

Fridges and freezers account for around 10% of the average New Zealand household’s energy use. They are the biggest consumers of energy of all household appliances because they operate continuously.

Their efficiency decreases as the temperature of their surroundings increases. Efficiency also depends on the level of insulation

They should be located in a cool area, not in direct sunlight, and away from cookers, dishwashers and other heat sources. A 75 mm gap should be left around all sides of a fridge or freezer.

Clothes washers and dryers and dishwashers

Clothes washers and dryers and dishwashers account for around 1% of the average New Zealand household’s energy use. These appliances should be sized appropriately for the household. If too small, they will be used more often; if too large, they require more energy to run.

Considerations when purchasing an appliance:

• Front-loading washing machines are more energy-efficient and water-efficient than top-loaders. They also generally have a higher spin speed, which means they remove water from clothes more efficiently.
• Gas-fired or heat pump-powered dryers are more energy-efficient than electric dryers, but they are not readily available.
• Clothes dryers must be vented outside via an exhaust air duct to ensure moist air is removed. This indirectly reduces space heating load, as extract ventilation does not need to be provided to the whole room.
• It is more energy-efficient and water-efficient to use a dishwasher than to wash dishes by hand.

Kitchen energy efficiency

The energy efficiency of the kitchen can be improved if:

• it has a rangehood above the cooking area to extract moisture without removing a large quantity of heated air from the rest of the house
• a heat recovery exchange unit is incorporated in the air extract system, which transfers extracted heat to an air or water heater
• the oven and cooktop are located on an internal wall so heat may be transferred to other rooms
• the oven is not located beside a refrigerator or freezer.