Energy

Energy can be saved by specifying energy efficient appliances that are sized for the household’s needs, and by locating them to minimise energy use (for example, keeping refrigerators out of direct sunlight). Designers should explain to householders other energy efficiency issues such as standby power.

Energy rating and labelling schemes

There are three main energy labelling schemes operating in New Zealand.

Energy rating labels are compulsory for fridges and freezers, clothes washers and dryers, dishwashers and air conditioning units. The labels contain a star rating for energy efficiency – according to the Energy Efficiency and Conservation Authority, each extra star means a 10% saving in running costs. For air conditioning units, separate ratings are provided for heating and cooling.

The labels also show energy consumption per year. It’s important to consider this because a large appliance with a high star rating can use more power than a smaller appliance with a lower rating. For dishwashers and washing machines, the labels also have to show information about standby power.

Information about energy ratings for appliances commonly available in New Zealand can be found at www.energyrating.gov.au.

The Minimum Energy Performance Standard (MEPS) sets minimum energy efficiency requirements for fridges and freezers, electric hot water units, and air conditioning units. All of these products must meet the MEPS standard.

Energy Star labels are awarded to products which have low energy use in stand-by and sleep modes. The scheme is being phased in, starting with home entertainment and electronic appliances (TVs, CD players, computers etc), as well as heat pumps and air conditioners. New products will be added regularly. You can find lists of Energy Star-endorsed products at www.energystar.govt.nz.Standby power

Many appliances have a standby mode, in which they’re not providing any useful output but are still consuming energy. Some appliances use standby power to light an LED display. Some are waiting for remote control signals to tell them to start operating, or are sending and/or receiving signals to other appliances (for example, home automation systems).

According to the Energy Efficiency and Conservation Authority, it’s been estimated that standby power accounts for 5 percent of total household energy use, or $100 million a year.

Average standby consumption for common appliances is: 2W for a computer; 3W for a dishwasher, DVD player, microwave oven or garage door opener; 5W for a TV or printer; 6W for a VCR; 14W for a security system. Standby power can be saved by turning appliances off at the wall if they are not being used.

Cooking appliances

Cooking accounts for around 6% of the average New Zealand household energy use. Most of this is used by ovens/cooking ranges. With most cooking appliances, only a small amount of energy is actually used for cooking; the rest heats the air around the food that’s being cooked.

Ovens

Gas ovens are more efficient than conventional electric ovens but gas requires a well ventilated kitchen and an extract is recommended. Specifying an oven with a fan is more efficient. Self-cleaning ovens are more efficient than other types because they have more insulation.

Wood-burning stoves are sometimes regarded as a sustainable cooking alternative, but they waste a lot of heat up the flue and into the room, have less heat control than conventional ovens, and produce emissions that may be harmful.

Solar or sun ovens use solar energy as a free heat source. They use reflectors to concentrate sunlight on a black cooking pot. Glass or plastic may be used to keep the heat in. Food can be baked, boiled or steamed. Solar ovens are the most energy efficient option, but they’re not yet commercially available in New Zealand.

Cooktops

When specifying or advising on the selection of a cooktop, the first choice is gas or electric. Generally gas is considered more efficient at transferring heat to the object on top.

If the electric is the choice or only option, the type of element must be chosen. The options, from most efficient to least, are:

• induction elements – use a strong magnetic field for heating, with the element staying relatively cool (these are currently the most expensive option)
• halogen elements – have bright halogen lamps under a glass top and give instant heat
• ceramic glass elements – have electric elements under a glass top, are easy to clean but can break
• exposed coil elements – conventional electric elements that are the most common, and lose heat to the surrounding air
• solid disk elements – require more energy to run, without delivering much more heat to the pot.

Microwaves

With microwaves, about 50% of the energy is used for cooking – this is far more efficient than any conventional oven.

Cooking appliance installations

The energy efficiency of a house can be improved when the design of the kitchen:

• includes a rangehood above it to effectively extract steam without discharging large quantities of heated moist air from the rest of the building
• has a heat recovery exchanger in the air extract system for transfer to an air or water heater
• has ovens and cooktops located on an internal wall so some heat is transferred to other rooms
• has the oven not sited alongside a refrigerator or freezer.

Fridges and freezers

Fridges and freezers account for around 10% of the average New Zealand household’s energy use. These are the biggest consumers of energy of all household appliances, because they are operating all the time. The energy efficiency of fridges and freezers decreases as the temperature of the surrounds increases and also depends on the level of insulation used in manufacture. They should be located in a cool spot out of direct sunlight, and away from cookers, dishwashers and other heat sources. A 75 mm gap should be provided around all sides.

Older refrigerants typically contained chlorofluorocarbons (CFCs) which can harm the ozone layer if released. Refrigerants used in New Zealand fridges and freezers include:

• R-410a – which is ozone-friendly and slightly more efficient
• R-22 – which is being phased out due to ozone damage and is also about 5% less efficient than R-410a
• R-290 – which is also known as propane and is highly flammable.

Clothes washers and dryers, and dishwashers

Clothes washers, clothes dryers and dishwashers account for around 1% of the average New Zealand household’s energy use. These appliances need to be the right size for the household. If they are too small they will be run more often, and if they are too large they will require more energy to run. When advising the owner or specifying:

• front-loading washing machines are considerably more energy efficient and water efficient than top-loaders; they have a higher spin speed which makes drying more efficient
• most clothes dryers are powered by electricity; gas-fired or heat pump powered dryers, if available, are more energy efficient
• clothes dryers must be vented outside via an exhaust air duct to ensure moist air is removed from the laundry – this indirectly reduces the space heating load by not having to provide extract ventilation to the whole room
• it’s more energy efficient and water efficient to use a dishwasher than to wash dishes by hand.

For your clients

To help your clients choose appliances and operate them efficiently to save electricity costs, refer them to www.smarterhomes.org.nz/energy/appliances.