As water prices have increased, so too have inquiries from people wanting to collect their own, tank suppliers say. But to make it worthwhile, you need to stay in your home for a long time.
In Auckland, Whangarei, Tauranga, Nelson and the Tasman District, homeowners are billed for their individual water usage.
From this week, Aucklanders pay $1.375 per 1,000 litres of water and $2.336 per 1,000 litres of wastewater. Watercare charges for wastewater at 78.5 per cent of the water used.
An average household uses about 177,000 litres of water a year, or $554.77 in water bills.
To put in a new tank costs about $3,000, Owen Dibley of Aqua Tanks estimates — so it may take five years to pay off the cost of a tank, excluding any council consent charges.
"It takes a while to break even," he said.
Gail and Frank Simons put in a small tank when they built their house at West Harbour.
"It would only pay off if you had bigger tanks and plumbed it into your toilets," Frank said. "We installed one to save a bit of money on watering the garden."
Growing vegetables gives you fresh produce on tap but won't always save you money. Chris Hall, of Kings Plant Barn, said the cost of setting up a vegetable garden varied.
You can spend hundreds of dollars on planter boxes, compost and dirt, or you can simply turn over a corner of your garden, put in seeds and hope for the best.
He said planting seeds would give you vegetables more cheaply than from the supermarket. A pack sells for about $4 for 100 seeds.
But growing seedlings is only a little cheaper than buying vegetables at supermarket prices. A typical seedling punnet may cost $5 for six to eight plants.
Growing tomatoes and squash tends not to be as effective price-wise because they are sold at deep discounts in the peak season, at the same time home gardens bear fruit.
Cabbage and broccoli take up a lot of ground but are cheap in shops.
Hall said people also needed to avoid ending up with a glut: "There's not much you can do with a dozen lettuces ready at the same time."
Grey Lynn man Bob de Soto has had a vegetable garden for two years, after spending $100-$200 setting it up. "The soil was pretty bad. But once you've got an established garden it's possible to save money."
He said it would work out cheaper to grow your own vegetables than to buy organic varieties from specialist shops.
"When things are growing the best and are in season, that's when they're super cheap.
"But I'd say there are benefits — it definitely tastes better and it's quite fun."
Backyard chickens provide a relatively consistent supply of eggs. Each chicken should lay five or so a week.
But at about $250 for the chicken coop and $20 for a hen, you could buy a lot of eggs — at about 60c per free-range egg from shops.
Hens lay for two to three years, and may stop in winter. You'll also need hay and feed. Pellets are $11.39 for 10kg from Countdown.
Heather Lowrie runs Backyard Chooks, which offers starter packs for chicken owners. She said people who bought free-range eggs would find owning chickens pays off within a year.
"I pay $10 a fortnight for pellets for three chickens. Hay might be 50c a week, and the only other thing is time — to feed them and clean out the coop."
Installing a grid-tied solar power system for $8,000-$10,000 can cut bills 30 to 70 per cent.
Roy Maddox of Solar King said a system generated about $1,200-$1,400 in annual savings for an average household.
"That's a 14 per cent return on the cost of the system and because it's a saving, it's not taxable," said Maddox. Most would find the system paid itself off in six to eight years.
The pay-off is greatest for people who use power during the day when it is being generated, because power companies pay less for power put back into the grid than they charge for power used.
Solar hot-water systems can cost $4,000-$10,000. Water can be heated entirely by the sun for five to seven months of the year, cutting power bills by 30 per cent.
Whangarei woman Liz Woodward said her system worked well. "It was $3,000 to buy and install. Electricity is turned off to the hot-water cylinder for eight months of the year and just used in winter to top up on gloomy days."
She said she spent $90.60 in the past year on heating water.
But Consumer NZ said it was not a reliable money-saver. "Any solar water-heater will have to pay itself off by saving a lot of money each year or by lasting a very long time without the need for repairs."
In many cases, the cost savings and longevity weren't enough, it said.