Choose the right water heating system
If it's time for a new hot water system, or you just want to save energy, then choosing the right system for your needs can help you reduce your energy use. As well as giving you lower running costs, an efficient system will help cut your household carbon footprint and ensure that more of today's resources are left for tomorrow.
On this page:
- Your hot water needs
- Options for water heating systems
- Costs of a hot water system
- Environmental impacts
Your hot water needs
Knowing how your household uses hot water will help you make better choices about getting the best energy efficiency and value for money - here are some things to consider.
- The size of your household: how many people live in your house now, and how many might there be in the future?
- How and when you use hot water: do you need a lot at once? For example, do six people want to shower in the morning? Does your dishwasher or washing machine draw on the hot water system?
- How much you pay now: look at your bills over a 12 month period or contact your energy supplier for help in calculating the cost.
- How much you'll pay with a new system: as well as paying for the system and its installation, you'll be charged for running it. You may also have to pay an ongoing supply charge.
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When designing a new home or changing the layout of your existing home, aim to have all areas which require hot water close together - your bathroom, kitchen, ensuites, toilets and laundry. As well as reducing the initial plumbing costs, you will save on energy costs as there will be less hot water wasted sitting in the longer pipes.
Options for water heating systems
There are two main kinds of water heating systems - systems that store water and instantaneous flow systems. The instantaneous flow systems heat water as it runs through rather than storing it, so they don't need a storage cylinder.
The common types of water heating systems on the market are listed below. Keep in mind that they're not all created equal - some types of water heating are more efficient than others, and efficiency can also vary between models of the same type. Some options will also help you reduce your environmental impact.
| Systems that store water | Instantaneous systems |
| Solar water heating | Instantaneous flow gas |
| Heat pump water heating | Instantaneous flow electric |
| Electric storage | |
| Gas storage | |
| Wood or wood pellet water heating |
Costs of a hot water system
Upfront costs
Generally, the upfront cost of a gas or electric system is between $1,500 and $3,000. A heat pump water heater costs between $5,000 and $7,000, and a solar water heating system between $4,000 and $8,000. These costs include installation and building consent costs, if applicable. [1]
If you are planning to install a solar water heating system, you may be eligible for ENERGYWISE™ funding.
Ongoing running costs
Ongoing running costs over a year can vary quite a bit depending on what water heating system you choose to use, how much hot water you use and your energy tariff.
As an example, the following graph shows costs for a typical three-person household. Running costs for larger households will be higher.
Click on the image below to view a larger version of the graph:
Environmental impacts
Choosing a hot water system that uses renewable energy sources like the sun or wood will reduce the environmental impacts into the future.
Whichever system you choose, using it efficiently will mean less energy and water is wasted.
Electric water heating
Electric storage cylinders are the most common form of water heating in New Zealand. An electric element heats the water in an insulated tank to a temperature set by a thermostat. The water can either be heated night or day, as it is used, or can be heated at night using cheaper, night rate, electricity ready for use the next day.
Newer electric hot water cylinders, installed after 2002, will be A-grade and well insulated. Cylinders older than that are likely to have less insulation or be uninsulated.
If the cylinder feels warm to the touch, it means you are paying to heat the air around the cylinder, not just the water. You can stop this heat loss by investing in a cylinder wrap. It will pay for itself in energy savings, and you can still use the hot water cupboard to air clothes and linen.
Even if it is a new cylinder, the first metre of hot water pipe near the cylinder still needs to be wrapped with insulation.
If you already have a night rate electricity meter at your home, night rate hot water is the cheapest option both upfront and on an ongoing basis. You might want to look at a larger cyclinder than was traditionally installed for night rate though, so you don't run out of hot water in the evening.
If buying a new electric cylinder, consider buying a ‘solar-ready’ tank. This can have a solar panel, heat pump water heater, or wet back connected to it easily in the future.
Instantaneous flow electric water heaters heat water as it runs through, so they don't need a storage tank. This reduces heat loss and means they use less energy than an electric storage cylinder.
Gas water heaters
There are several gas water heating options that can use natural gas piped to your house from gas mains or LPG from bottle or, in some areas, gas mains. These include instantaneous gas heaters and gas heated hot water cylinders.
Instanteous gas heaters avoid the potential heat losses from a cylinder. They are up to 95% efficient (95 cents worth of hot water for every dollar of gas used). They can have the added benefit of freeing up some storage space in your house if a cylinder is removed.
Gas hot water cylinders can go inside or outside your house. If considering a gas hot water cylinder, condensing systems are the most efficient type. These, however, have to be located outside.
Adding a wetback to a wood or wood pellet burner
Many wood or pellet fires, ranges or burner systems can have wetbacks fitted to them. This can work as a valuable supplement to your hot water system.
A wetback is a pipe arrangement that fits in the back of the firebox and uses some of the heat from the fire to heat water. Adding a wetback to a new or existing burner does have one important implication – you will get less heat in the room than you would without the wetback.
The type and location of your hot water cylinder can often determine if you can fit or use a wetback. Check with the fire manufacturer and a plumber.
