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Designing homes to conserve energy and use it efficiently, from sources that cause least environmental harm.
Selecting energy-efficient appliances
Energy use can be minimised by the selection of energy efficient appliances.
On this page:
- Energy rating and labeling schemes
- Microwave ovens
- Fridges and freezers
- Clothes washers and dryers, and dishwashers
There are two factors to consider. The first is the type of appliance – some are more efficient than others (for example, induction elements are more efficient than other types of electric cooktop element). The second is to use a rating or labeling scheme to select an efficient model for the type of appliance specified.
Energy rating and labeling schemes
The three main energy labelling schemes operating in New Zealand are:
- energy rating labels
- Minimum Energy Performance Standards (MEPS).
Energy rating labels
Energy rating labels are compulsory for household fridges and freezers, clothes washers and dryers, dishwashers, televisions, computer monitors, air conditioning units and air-to-air heat pumps. The labels contain a star rating for energy efficiency – each star means a 10% saving in running costs. For air conditioning units, ratings are given separately for heating and cooling.
Fridges and freezers and heat pumps/air conditioners can get up to 10 stars – extra stars appear in a crown above 6-star band.
The labels also show energy consumption per year. This is an important consideration, as a large appliance with a high star rating will use more power than a smaller appliance with a lower rating for the same level of use. Use the annual energy consumption figures to compare appliances of a similar type and size. Air conditioning units/heat pumps have different measures of power use: capacity output is the amount of heating or cooling (kWh) produced by a heat pump at its rated capacity, at 7˚C; power input is the amount of electricity the product uses (kWh) to produce cool/hot air. For dishwashers and washing machines, the labels are also required to show information about standby power.
Minimum Energy Performance Standards (MEPS)
The Minimum Energy Performance Standards (MEPS) set minimum energy efficiency requirements for fridges, freezers, electric hot water storage units, gas water heaters, televisions, air conditioning units/heat pumps, fluorescent lights and compact fluorescent lights (CFLs). All of these products must meet the MEPS.
Running costs calculator
The government’s Energywise website has a running costs calculator for whiteware appliances, televisions, computer monitors and heat pumps. You answer a few questions about your appliance use, the size of appliance and its energy rating, and the calculator tells you the annual running cost. You can make comparisons between brands, models and sizes.
The Energywise website also has a tool called Rightware that shows product details, efficiency ratings and annual running costs voluntarily supplied by manufacturers and importers. Various filters can be used to help selection.
Cooking accounts for 5% of the electricity used by the average New Zealand household. 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.
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.
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 17% of the electricity used by the average New Zealand household. 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 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. Condensing clothes dryers do not need to be vented.
- 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.
- www.eeca.govt.nz – minimum energy performance standards
Updated: 17 September 2018