Huge electricity savings can be made by replacing old fridges and freezers - but it's worth hanging on to your ancient washing machine and dishwasher.
Lurking in homes across the country are refrigerators, washing machines and driers nearly as old as the inventions themselves - and these energy-hungry dinosaurs are adding hundreds of dollars to power bills.
Figures from Fisher and Paykel and the Energy Efficiency and Conservation Authority show the hungriest appliances are fridges and freezers - a 10-year-old fridge will generally cost a third more to run than a newer model. A 20-year-old model will cost double that.
A 16-year-old fridge recently dropped off at Fisher and Paykel's recycling centre was eating up $264 a year in electricity - more than double what a new model would cost to run.
Similarly, a 20-year-old chest freezer will add more than $200 a year to your power bill over a newer model.
The newest generation of fridges and freezers contain computer chips to monitor use and distribute cool air only to areas needed.
Fisher and Paykel is testing a piece of technology that has zero "global warming impact" and is 30 per cent cheaper to run.
On the other hand, an old dishwasher will not be causing much damage to your power bill. A new model will cost around $28 a year to run, based on daily use. A 2005 model will cost $30.60 and a 1995 model just $8 more.
However, Consumer NZ adviser Hamish Wilson recommends buyers be wary of some cheaper "energy efficient" dishwashers, as the power saving can compromise quality.
"It can be a trade-off. A low energy model will probably leave the dishes slightly wet at the end of the cycle. That's because, to get them dry, you have to burn the water off with heat, and that chews up a lot of energy," he says.
There are fewer gains to be made in replacing old clunkers in the laundry. Since 1990, the energy used by comparative washing machine models on a warm-wash cycle has stayed the same. And unlike fridges, washing machines do not get more power reliant as they age.
The exceptions are the machines designed to be energy efficient. Fisher and Paykel's new "AquaSmart" model costs around 40 cents less in electricity for every warm cycle - $150 over a year of daily washes.
In the laundry, it is water efficiency rather than electricity efficiency that will make a real difference to your bill.
A washing machine from 1990 will chew through an extra $150 worth of water a year (based on Auckland rates), Wilson says.
A typical drier from 25 years ago will cost around $2.88 to run for one hour, 24c more than a 20-year-old model and 48c more than a brand new one.
Machines do job at a cost
Linda Brown, 61, has replaced her dishwasher and oven twice in the past five years because each time she moves house the old ones don't fit into the kitchen space.
She retired her 15-year-old washing machine recently, too, but says she doesn't notice a difference in the new model.
On the other extreme, Auckland nurse Jane, 64, was the first of her friends to have a dishwasher and is proud to say it still washes the family's dishes each night 25 years later. In her garage is a chest freezer which has been buzzing away for more than 35 years. But it is costing her hundreds of dollars a year.
In Auckland, Fisher and Paykel offers a free recycling service for all brands.