Getting into hot water

by Andy Bryenton

Approximately one-third of the average Kiwi power bill comprises water heating, and we use hot water for so many applications around the home that it’s hard to conceive of a time, not so long ago, when boiling a copper kettle was a time-consuming chore. Our ancestors did without electricity, but we can’t so the best option for the modern home is to cut back that bill using technology.

Perhaps the simplest and most time-tested method is to plumb a wood-burning fireplace into a specially adapted cylinder. This wet-back method works fine in rural areas where emissions rules are lenient, and firewood is plentiful, but it has the added drawback of summertime inconvenience. A hot shower and clean dishes are still a priority in summer, but a blazing hearth is not.

Hence the popularity of a technology, which is still just catching on in New Zealand, despite massive popularity overseas. Heat pump hot water systems use the same efficient heat exchanger principle as those heating and cooling appliances, which are not a fixture of many living rooms.

Instead of heating air, they heat water, expelling cold air from a unit outdoors.

Some hot water heat pumps are designed as a single unit and are fitted outside, but for obvious reasons storing a cylinder of hot water out of doors in a southern winter is counterproductive. Thankfully, Kiwi designed and built systems exist that replace the old ‘boiler’ cylinder and its element, leaving just an unobtrusive box tucked away in the garden.

Savings are highest for homes with high hot water use. It may still be more economical to switch to a gas califont for those who live alone or whose children have moved out. Moreover, savings in the hundreds of dollars have been accurately reported by users. There’s also the option to boost the power of a hot water heat pump with solar hot water heating panels in the summer, further increasing efficiency. For those considering a bathroom renovation or a new build, it’s certainly something to explore.