Heating & energy
Power-saving gadgets
Introduction
Power-saving gadgets reduce wastage by measuring your power use or controlling appliances. We check out how they work.
Electricity is expensive. You can do yourself and the country a favour by tracking down wastage in your household - and reducing it. But what's worth worrying about and what's not? Power-saving gadgets can help.
What's using the power
Two types of appliances help rack up your electricity bill.
The first are appliances that use a lot of power while they're going, but don't run all the time. Electric heaters, dishwashers and clothes dryers fall into this category.
You can make savings by using these appliances only when you really need to - like waiting until the dishwasher is full before running it, and drying clothes on a washing line whenever possible.
The second group is less obvious. We're talking fridges, freezers, cupboard heaters, microwaves, towel rails, TV set-top boxes, DVD players and other appliances left on continuously. They often use little power individually - but when several are left on all the time, the results hurt when the power bill comes in.
Savings with this group can be made by being vigilant. Often a simple timer can reduce overall power consumption by cycling appliances on and off. And you can switch off devices left on standby when they're not being used.
Measure-my-use gadgets
Mains-power meter
The Centameter tells you how much power you're using as a household. It costs $190, although a small discount is available for customers of some power retailers.
It's supplied with a sensor - you need to get an electrician to clip this around the main power feed at the back of your meter board. The sensor connects via a cable to a battery-powered transmitter unit mounted on the wall close to the meter board.
The transmitter sends the amount of electrical current you are using to a battery-powered display unit (pictured right), which can be placed somewhere convenient.
You set up the display unit using the nominal voltage (230 volts) and the cost per unit you pay for electricity. (You can even set the greenhouse-gas emissions per unit of electricity - not very useful here because our electricity is generated from a mix of sources that change with circumstances.)
Usually you'd chose to display either your household power use at any given moment, or its cost per hour.
Finding out what any individual appliance contributes to your electricity load is fiddly, though. First you note your total power reading with the appliance going. You then switch off the appliance and note the new reading. The difference between the two readings is the appliance's power consumption.
Plug-in meter
The Elto power meter ($20 to $25) works a little differently. You plug the Elto into a socket and then plug the appliance into the Elto.
The Elto can be set up to display technical information like voltage, current, frequency, power factor, watts, and kilowatt hours. But for most householders the most useful read-out will be running costs. Key-in the price you pay for electricity and the appliance's running cost in cents per hour is displayed.
Are they any good?
Neither the Centameter nor the Elto power meter are laboratory test instruments and so their accuracy is limited. But they do give a good enough indication of the running costs of your appliances - with one exception: they're not accurate at measuring small amounts of electrical current (less than one amp). So they're not likely to accurately tell you the standby power consumption, but they could be useful for comparisons between appliances.
The Elto is likely to be more accurate than the Centameter if you want to measure the power use of appliances with motors in them - such as heat pumps and washing machines. (Why? See "Pointy-head techie talk" below.)
Pointy-head techie talk
To calculate electrical power accurately you need to measure both the supply voltage and the electrical current the appliance is consuming.
The Centameter measures electrical current but not the voltage. It assumes the mains voltage stays constant at 230 volts. Because of this, it'll overstate the power use of some appliances - especially those that have electric motors (for instance, heat pumps).
The Elto power meter measures both voltage and current. This means the Elto can calculate a thing called the power factor, so is likely to be more accurate for appliances containing motors - and for occasions when the mains voltage supply varies from the nominal 230 volts.
Save-me-money gadgets
This group of nifty gadgets help reduce your power consumption by controlling lights and other appliances that are often accidentally left on. They're especially useful if you have household members who leave on lights or towel rails.
Programmable light switch
If your house is frequently lit up like a Christmas tree, the IntelliSwitch ($80), pictured, could be worth a look. It can operate in three settings: a normal on-off switch, a controlled timer switch (which allows your light or appliance to be on for between 15 minutes and 3 hours), and in a "towel rail mode" (4 hours on, 8 hours off ... continuously).
The switch can be bought in one of four versions: single switch, double switch, three-pin socket, and a version for wired-in appliances like towel rails. You can legally install them yourself, if you live in the house and own it - but get an electrician to do it if you're unsure about messing with electrical wiring.
The possible savings with the IntelliSwitch depend on the type and number of things the switch is controlling. For a single energy-saver lamp the savings would be slight. But for a ceiling full of incandescent or halogen downlights, or a towel rail, they could be significant (see table above).
We tried it
We decided to try an IntelliSwitch in a basement laundry where previously one family member had the habit of switching the light on, sorting out some laundry, and then walking out leaving the light on. Sometimes the light would burn for over 24 hours until someone else had some laundry to do. Asking the family member in question to switch the light off was attempted (several times) but the attempts failed.
Installing the IntelliSwitch was straightforward: the unit replaced a standard light switch.
The laundry light now switches off after 15 minutes. No complaints and no electricity wastage, although the savings on one light are relatively minor (see table).
Towel-rail timer
Over a five-month winter, leaving one towel rail switched on all the time could cost you between $43 and $57.
Enter the Celsius Heated Towel Rail Timer. This $39 device can control up to five 100W towel rails - but it must be installed by an electrician. It saves power by automatically switching the towel rails on and off. The times are initially set as 4 hours on and 8 off, although the "on" times can be extended up to 11 hours by flicking the switch a specific number of times.
Report by Bill Whitley