Solar water heating

Water heating typically makes up 30% of your household energy bill. The good news is that many homes in New Zealand are in reliably sunny areas – well-placed to harness the free energy of the sun for solar water heating.  But solar water heating doesn’t mean having lukewarm water on cloudy days. With a backup system you should always have enough hot water for your needs.

On this page:

Why choose solar water heating?

Is solar water heating right for me?

Things to consider when choosing solar water heating

Why choose solar water heating?

Solar water heating can:

  • Lower energy bills
  • Lessen your impact on the environment

  • Add value to your home.

You could qualify for a $1000 ENERGYWISE™ grant to install solar water heating.

Lower energy bills

A well designed and installed solar water heating system will heat 50-75% of your hot water every year.

In summer you may be able to get all your hot water from your solar water heating system. In winter, or on less sunny days, you’ll need some extra heating from your ‘booster’ gas, electricity or wetback supply.

How much money you save from solar water heating will depend on a number of factors. These include how much hot water you use, how well the system is designed to meet your needs, and the quality of the installation.

For an average household an effective solar water heating system will:

  • Cut between 1,800 kWh (kilowatt hours) and 2,700 kWh from your annual electricity use
  • Save between $350 and $500 a year, depending on the cost of your electricity or gas supply.

Use this solar calculator to work out how long it will take for your solar water heater to pay itself off in savings.

Good for the environment

With a solar water heating system you’ll also be helping to reduce New Zealand’s dependence on non-renewable energy sources.

Each household solar water heating system is estimated to save between 360 kg and 1.6 tonnes of greenhouse gas emissions a year. This is compared to using a standard electric hot water tank. [1]

Add value to your home

As energy efficiency becomes an increasingly hot topic in New Zealand, installing solar water heating may add to your resale value. It also protects you against potential energy price rises in years to come.

Is solar water heating right for me?

The design and location of your house determine how easy it is to have solar water heating installed, and how well the system performs.

You’ll need a section of roof that:

  • Faces north (or close to it)
  • Has good, all year-round sun
  • Is large enough to accommodate collector panels, which usually means roughly 1m2 for each person in the house
  • Is near the hot water tank, your bathroom or laundry.

In an existing house you may need to add pipes in parts of the house that are hard to access. You may also need to add structural framing in the roof so it can carry the extra load of the panels and tank. 

Another option to consider, especially if you don’t live in a particularly sunny location, is a heat pump water heater.

Things to consider when choosing a solar water heating system

There are a number of different kinds of solar water heating systems to choose from.  To get the right one for your situation, the main things you need to consider are:

  • The appropriate size for your household
  • A system that performs well, in the climate you live in.

Size

The size of the hot water tank in your system needs to be matched to your hot water usage and the size of solar collectors on your roof. If your tank is too small or too big you will be paying extra to boost the temperature of the water.

A specialist solar water heating tank has extra water and thermostat connections. This type of tank is specially designed to maximise the use of solar energy. Your system is likely to perform better with one of these.

A standard hot water tank can be adapated, but these usually have a capacity of 180 litres. This is generally too small for a solar water heater to achieve optimal performance for a household of three or more people.

Performance

Suppliers typically offer packaged solar water heating systems.  These include:

  • The collector (solar panels)
  • The storage tank (cylinder)
  • The circulation system
  • Controller or timer.

The overall efficiency of your system depends on the perfomance of each component and how well they are matched together as a system.  In frost-prone areas you'll need to ensure your system has frost protection. This is important as the water or fluid could freeze in the collector panels otherwise.

A simple check of quality is to ensure that all components meet the standard AS/NZS:2712.

EECA lists the indicative energy performance information for all packaged solar water heating systems that qualify for an ENERGYWISE™ grant.  To compare the performance of these solar water heating systems, check out the EECA's list of solar systems eligible for a grant.

Case studies

Tasman couple Vivien Edge and Ken Ross enjoy hot water heated almost entirely from the sun for eight months of the year, after installing a solar hot water system in their Upper Moutere rural property. Read more about their solar project.

Tracey and Robbie Torrance of Richmond upgraded to a solar water heating system to reduce their power bills and increase the availability of hot water. This case study describes how Tracey and Robbie reached the decision to install solar water heating, covered the costs of the project with help from an EECA ENERGYWISE™ loan, and worked with their installer for a hassle-free upgrade. Read more about their solar project.

More information

 

Notes:

[1] Based on average savings of between 1,800 kWh and 2,700 kWh a year and an electricity emission factor of between 200 kg/MWh (replacing an old water heater) and 600 kg/MWh (putting a solar water heater on a new house).

From the Resource Centre

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